Weather Flying
Robert N. Buck
Robert O. Buck
Fifth Edition
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For Leighton Collins.
About the Authors
Robert N. Buck (1914–2007) was a leading aviation author who set a New York
to Los Angeles speed record in 1930 at the age of 16. He began a career with
TWA in 1937, initially flying the DC-2 and DC-3. During World War II he flew
with the Air Transport Command, until as a civilian he headed a bad-weather
research project for the U.S. Army Air Forces, flying a Boeing B-17 bomber; for
this he was awarded the Air Medal. He also participated in early thunderstorm
research, penetrating storms in a P-61 Black Widow. Post-war he was briefly
TWA’s chief pilot, then returned to the cockpit to fly over 2,000 trans-Atlantic
crossings, as well as served on numerous aviation committees on safety, weather,
and U.S. supersonic transport efforts. He retired as a Boeing 747 captain, then
remained active through aviation consulting, wrote four more books, and
remained an active pilot until age 88.
Robert O. Buck is a retired Delta Air Lines captain, with roots in general
aviation, where he remains an active pilot, flying light aircraft and sailplanes. He
soloed gliders at 15 and a beloved Cessna 120 at 16, and retired flying Boeing
767s internationally. His aviation path has also included competitive soaring,
flight instruction, aircraft sales, commuter airline flying, and serving as Technical
Editor for Business & Commercial Aviation magazine.
Contents
About Some People
Preface to the Fifth Edition
Introduction to the First Edition
1. Weather Flying
2. A Little Theory for Weather Flying
That Important Dewpoint
How Air Cools
Season and Time of Day
Terrain
Wind
Clouds
3. Some Thoughts on Checking Weather
It Isn’t Easy
It’s Approved and Official
How It Works
You Are the Meteorologist
You Are the Captain!
4. Checking Weather and the Big Picture
The Big Picture
No Surprises
Satellites and Some NEXRAD
What Do Satellites Show?
Valid Old Map Thoughts
Where We Find This Computerized Weather
Get the Picture First
On Days Off, Too
A Deeper Look at the Map
Watch the Slow Lows
The Wind Speed Tells a Story
Highs Are Not Always Nice
Look Up
A Meteorologist’s Big Picture from the Web
5. Getting That Weather Information
Always Learning Where and How
Some Extra Sources
No One Said It Was Easy
Hired Help
Opening Remarks to the FSS—and Ourselves
Synoptic Again
Look Ahead
The Real Thing
6. Weather Details—What They Tell Us
VFR—Not Easy
MVFR
MVFR Is Not Static
IFR—Not to Worry
Test the Forecast
The Late Weather
Regulations Aren’t the Important Criteria
Pollution and Visibility
How Do You Feel?
More about Wind
Altimeter Setting
Temperature and Dewpoint Again
PIREPs
On the Ground, Too
Summing Up
7. Checking Weather for the Route
Weather Is Mostly Good
Something on Fronts
Occlusions and Zippers
Large-Area Weather
The Important Northeast Corner
Go the Short Way
It Takes Time to Know
Why and If
Don’t Fear Weather …
… Or Worry about It
8. Equipment Needs for Weather Flying
It’s Farther Than You Think
Fuel and the Law
Fuel Again
Instruments and Autopilots
Where the Instruments Live
We Can Keep It Simple
A Little More to Do a Lot
Things Can Be Better
Even Better
The Future Will Be Even Better
The Protected Airplane
Power for Instruments
Lighted Well
Paperwork and Gadgets Are Equipment, Too
Go Fast Slowly
Good Housekeeping
An Extra Hand
Navigation
Radar and Lightning Detection Systems
9. Temperature, an Important Part of Weather Flying
Temperature and Density
We Better Figure It Out
How Hot, How High?
Engines Don’t Like It Hot
10. Some Psychology of Weather Flying
Self-Discipline
Think, for Real
11. Turbulence and Flying It
Kinds of Turbulence
How We Fly Turbulence
Convective-Layer Turbulence
It’s Rougher Than You Think
Dust Devils
Turbulence Near Mountains and Ridges
Mountain Waves
Turbulence Up High
Where Is It?
The Tropopause and CAT
The Tropopause Is Important
Shear
Where Is Shear?
Thermals
12. VFR—Flying Weather Visually
VFR
The Famous 180
A Point to Remember
Snow Is Different
Keep Calm
More Snow
Towers
VFR Navigation—and the Important Map
Not Only Airports
Where Is the Wind?
Near Cities
Summertime
Thunderstorms and VFR
VFR on Top
Using Electronics When VFR
Without Radio
13. About Keeping Proficient Flying Instruments
Practice
Self-Checking
With Full Instruments
14. Thoughts on Flying Technically Advanced Aircraft
Single-Pilot Operation in a Two-Pilot World
Dependence on Augmented Indications
Electronic Seduction
Programming Thoughts
Summary of Flying Basics in a Technically Advanced World
15. Thunderstorms and Flying Them
What Are They?
What Is Tough about a Thunderstorm?
Tornadoes
Hail
The Bad Part
Their Life Cycle
A Clue
The Different Kinds
How High?
The Cloud Layers
They Grow Fast
What’s Inside All Those Clouds?
What’s Outside All Those Clouds?
Thunderstorm Detection Systems
Airborne Radar
NEXRAD
Lightning Detection Systems
Data-Linked Lightning Mapping Information
ATC and Thunderstorms
More about Air-Mass Thunderstorms
A Cloud Base Hint
Other Air-Mass Thunderstorms
Dry Climate and Thunderstorms
Frontal Thunderstorms
The Surface Wind Tells
How to Tell a Front’s Toughness
Prefrontal Squall Lines
Some Rules
If We Fly Through
At Night
Where to Bore In
How to Fly It
Are We Scared?
Something to Be Said for Rain
Fly!
Electrical Discharge
Static and Radio
The Noise Is Annoying
Almost through the Storm
Warm Front Thunderstorms
Low Down
Thunderstorms as We Arrive and Land
Don’t Race Thunderstorms
Missed Approach in Thunderstorms
After the Missed Approach and Other Thoughts
16. Ice and Flying It
About Ice
Dealing with Ice
The Propeller Is Important
Wing Deicers and Anti-Ice
Boots
Hot Wings
Fluid Anti-Icing
We Have to See
How We Fly Ice
Is Your Airplane Equipped to Fly Ice?
Propellers, Jet Inlets, and Other Fixtures
Ice Flying Starts on the Ground
Where We Find Ice
Temperature Again
Where Are the Tops—and the Bottom?
Fronts and Ice
An Ice Airplane
Not Always in Clouds on Instruments
Warm Front
Fishing to Get Out of Ice
Taking Off in a Front
Learning Time
Orographic Effect Again
Cold Front
Flying to Feel Ice
Coming Home
17. Taking Off in Bad Weather
Altimeter Setting
Be Prepared
Let’s Go
Radio Thoughts
Don’t Be Bashful!
Off We Go
In the Stuff Quick
How about the Weather?
Once in the Air
Thunderstorms Again
Thinking
18. Weather Flying En Route
Think Ahead
What’s It Like?
Forced Landing with Little Time to See
All Is Normal and It’s Time to Get There
19. Landing in Bad Weather
Flying the Approach
The Instrument Part
Close in, Things Get Tight
Stick with It
When We See Again
Autopilots Doing the Work
Circling to Land
To Touch the Ground
Low Visibility
Ground Fog
On the Ground
An Approach Briefing
The Toughest Case
20. Teaching Yourself to Fly Weather
Where’s the Emphasis?
Learning the Weather
21. Something on Judgment
Limitations
Suggested Reading and Websites
Acronyms and Contractions
Index
About Some People
There are many people to thank for helping me with this book. It starts with a
meteorologist named Mr. Ball, who, when I was sixteen and starting across the
United States alone, briefed me at Newark Airport, New Jersey, on what the
weather would be. I was interested in what he said because I didn’t know much
about weather, or flying either, and I was a little nervous.
Mr. Ball—I never knew his first name—also awakened my interest in weather,
what makes it, and what a pilot does about it. Looking back, I realized that Mr.
Ball was an exceptionally good meteorologist.
After Mr. Ball came a host of meteorologists, most of whose names I don’t
know and never will. They are voices and faces over a telephone or in a weather
office in some city when I was trying to make cross-country records, or just going
somewhere.
Some time later they were in wood-paneled rooms in Gander, Newfoundland,
or Prestwick, Scotland, during World War II, when the Atlantic, sitting out there
waiting to be crossed, was a big, black unknown, and whatever that man said I
listened to carefully because any crumb of information was something to grab for
help in doing a job that I didn’t know all there was to know about doing.
There are meteorologists I got to know well by searching conversation as I
tried to learn, and later in consultation as we probed the atmosphere in research—
men like Ed Minser and J. A. Browne of TWA. I continued to learn from TWA
meteorologists who briefed me on what the weather would be over the North
Atlantic, which became an ocean I respected but felt very comfortable flying over
in a 747.
There is Nieut Lieurance (retired) of the National Oceanic and Atmospheric
Administration (NOAA). Nieut is a pilot’s meteorologist and has done much to
bring good weather services to us all. Chuck Lindsay (retired) of NOAA is one of
the world’s foremost soaring meteorologists and a person always good for a new
piece of knowledge. I thank Chuck also for reading the manuscript of the first
edition and making some valuable suggestions.
Lt. General Ira C. Eaker, a boyhood hero of mine, saw the possibilities of
thunderstorm research and made it possible for TWA and the U.S. Army Air
Forces* to work together using a P-61 Black Widow night fighter, which I was
fortunate enough to fly in the project.
Captain Robert A. Wittke, TWA (retired), my close friend since childhood,
made useful and perceptive suggestions.
Also, Dan Sowa, the superb meteorologist of Northwest Airlines, has given me
many insights into the mysteries of weather, as has his associate, the brilliant
technical airman, Captain Paul A. Soderlind of Northwest Airlines.
I’m indebted to my good friends at the National Weather Service in
Burlington, Vermont, and the staff at the Flight Service Station in Burlington,
Vermont. These men and women have been ready and most willing to patiently
answer my questions and enthusiastically dig out information for me. I especially
thank Ben Martin, Betty Czina, and Jimmy Mason of the FSS and William Grady
of the Burlington NWS.
Years ago, I learned from Dr. Horace Byers and for a brief but exciting and
privileged time from Dr. Irving Langmuir.
I wish I could name all the others, but there isn’t space. I do want it to be
clear, however, that I thank all meteorologists. They are a misunderstood group
who are cussed more than praised, when it should be the other way around.
I want to thank Velma and Dwane Wallace for urging me to get this book
done.
Solid advice and encouragement came from Charles W. Ferguson and
Caroline Rogers of The Reader’s Digest . They were patient and understanding
friends.
I must mention the man to whom this book is dedicated, Leighton Collins,
who with his Air Facts magazine started me writing about weather almost 50
years ago. His enthusiasm and encouragement did the most.
My wife Jean, daughter Ferris, and son Rob, captain on a major airline and an
experienced weather pilot who shares my weather interest and study, all gave their
enthusiastic support, and I thank them for that.
Robert N. Buck
Fayston, Vermont
This version of About Some People is from Weather Flying ’s 4th edition (1998),
and the last revision from the original author, Robert N. Buck (Bob Buck). Since
then, a majority of the folks mentioned have left us, save for my (ROB) sister,
myself, and the folks from the Burlington, Vermont, FSS and NWS. The
Burlington FSS has closed as part of the FAA’s centralization of the FSS system, I
have retired from Delta Air Lines, Northwest Airlines has merged with Delta Air
Lines, and TWA became part of American Airlines. The weather, however, is still
out there waiting for us.
* The United States Army Air Forces of World War II became the United States
Air Force in 1947.
Preface to the Fifth Edition
Crew Change
In the late spring of 2010, my youngest son and I flew our single-engine Cessna
170 from Vermont to the West Coast and back, the trip a father and son adventure
with a nostalgic twist. We retraced a good portion of my father’s 1930 record
flight from New Jersey to California, his adventure flown in an open-cockpit
Pitcairn biplane when he was just 16 years old. That daunting trip was my father’s
first experience in blending aviation’s utility with weather, arguably sowing the
seeds that blossomed into this book called Weather Flying .
Our trip also traversed routes he had flown in TWA DC-2s and DC-3s, starting
in 1937. We thought it interesting that our little airplane wasn’t that much slower
than those Douglas transports and flew at the same altitudes. They battled ice, fog,
turbulence, and harrowing thunderstorms, sometimes flying right through them,
but obviously found good weather, too. We didn’t feel that historically
compulsive, so took the good-weather route.
Our trip also brought fond memories of years I’d spent flying with my father,
both hanging out together, as well as cutting a wide swath through aviation’s field
of dreams. He didn’t smother you with aviation, instead more along the lines of:
“I’m going flying, and if you want to come along I’m leaving in an hour.” I was
ready the moment he said it. If you flew enough with the guy who wrote Weather
Flying , you soon learned this weather and flying relationship was a big deal. His
enthusiasm for the fascinating riddle of weather was infectious, and one quickly
learned that heeding it not only made flying work better, it also kept pilot and
airplane safe to fly another day. Those years were the show-and-tell, lab-class
version of Weather Flying .
When this book made its debut in 1970, a lot had changed since those DC-3
days. It was the year my father checked out on TWA’s shiny new gentle giant, the
747. At the same time, I was working on a formal education that posed
competitive quandary towards an obsession to flying, which included earning
pilot ratings and building flight time. In four years my father would retire, and I
was headed out into my own career. Eventually it would fortuitously find a
forward window seat in an airliner, but not without holding fast to my general
aviation roots.
My career began about where my father’s ended, flying good old round-dialed
analog airplanes, straight forward autopilots, and fair amounts of close-in hand
flying, along with crafty pilots who skillfully mentored the tricks of trade. And
then it began to change forever … our era was straddling the transition to today’s
world of electronic flight instruments, programmed everything, and advanced
automation. Some went kicking and screaming, but more importantly, when new
technology caused a quandary with an airplane and/or pilot, old-school flying
sense provided the tools to think simply and use hand-flying basics, keeping us
upright and aimed in proper direction, then fix it when all calmed down. It was
nothing special; instead, just logical flow from what everyone was used to doing.
This matching of eras was fortuitous when old flying dogs had to learn new
tricks. It’s now been a generation since this technology has come along, and today
we find both airlines and general aviation vying for the fanciest and newest
technology of aircraft equipment; and with that, arguably, a developing over
dependence on the technology. We see a gap developing between old-school
thinking that brings airplanes home versus detached thinking, or lack of flying
basics, that doesn’t. Not all the new dogs are learning old tricks. Whether they’re
misunderstood, not being taught, ignored, or even more sobering becoming lost
art, old-school flying thought and skills are being left out of the equation; and
with that an unfair blaming of this superb new electronic world. From little
airplane to big, flying high or low, privately or professionally, there are too many
red flags and rustling leaves.
Another twist of technology that blends into this book’s new edition relates to
that all-important gathering of weather data, as we prepare our flights in today’s
computerized world; it has become a lonely task. My son and I saw it on our
cross-country journey, before leaving on a leg from St. Louis to Kansas City: we
orchestrated the whole weather briefing on a smartphone. That was a first for us,
and included the whole deal—weather data, maps, radar, winds, and more, then
finally the phone call to a briefer for an update and to file a flight plan. I told my
son there was once a time when you could walk into a weather office or Flight
Service, talk with a briefer eye to eye, and have their knowledgeable assistance
while looking over the data. Whether you were a new pilot or one with thousands
of flying hours, it was a learning experience. Even granddad, I told him, who
understood weather as well as anyone, relished the opportunity. My son’s quick
mind of youth realized that meant today’s pilots better know this weather thing
cold; especially after he saw that flashing, seething mass of thunderstorms half
way to Kansas City, as we turned left and diverted to Wichita.
When the opportunity came along to revise this sage text, my primary task
was not to mess with the book’s core, whose respected story of 43 years tells us
how to fly weather with practical understanding. My father had a knack for telling
a story with concise and comfortable simplicity, and frankly that’s how we should
think about flying. If there is any doubt of this seasoned book’s currency, we need
to remember that the sciences of weather and how airplanes fly have remained the
same since time began, as is the science of bringing the two together. And it’s still
the same stuff even if masked by sleek, powerful airplanes with magnificent
electronics.
One of my father’s memorable comments was something to the effect of:
“Folks jump into equipment they aren’t ready for, depend on the gadgets to pull
them through, then take off and get in over their heads.” It’s obvious what can
happen next. He said that decades ago, but the same unnecessary endings are
being repeated today. These fantastic modern electronics are perfect for serious
weather flying, and a majority use them well, but the equipment also puts us in the
professional realm of more study and practice. Today, the task of managing the
airplane, pilot and weather is a new ballgame!
So this edition’s new writings connect Weather Flying with today’s world of
computerized and electronic weather data and aircraft equipment. We also found a
few new twists in weather science, but again, working to retain the book’s
respected core. This edition does not tell us how to operate every little button or
computerized application. Instead, there’s discussion on how we merge this
technology into our weather planning, then once airborne, use electronics
prudently, while blending the whole process with disciplined thought and flying
basics; including a higher bar of training. And very important is not misusing
technology as a replacement for a pilot’s ability or knowledge.
On the bright side of flight, as my son and I roared along behind our
Continental engine’s six little cylinders, part of my job was placing my father’s
stories into context and in some cases, over almost exact locations. We pondered
his explanation of how he survived flying across the country at age 16, with only
97 hours in his logbook and in a far less air-savvy era; but his generation lived
with basic sense! He said the key was being taught how to fly well, practice,
improve, think, and not push the weather. It’s still that simple today, almost a
century from those early days of aviation!
When my father flew weather research during WWII, he had a plan and
limits; maybe not ours, but certainly his and the airplane’s. I also told my son that
his grandfather was one of the most conservative pilots I’d known, especially
considering his credentials.
And remember the thought of flying at DC-3 speeds and altitudes? Well, that’s
where most general aviation aircraft still fly, and a little turbocharging or
turboprop performance has us up there with the B-17 bomber and P-61 Black
Widow my father used in weather research, with the same turbulence, ice,
thunderstorms, and other meteorological angst, but also the same beautiful sky.
So, when you read Weather Flying’ s references to lessons learned in DC-3s, the
B-17, and later craft, we’re still pretty much in the same corral. The weather sure
doesn’t know the difference, nor do aerodynamics!
With the little stories throughout the book, you’ll see a little “RNB” for my
father’s yarns, and “ROB” for mine. We should remember his era’s stories were
from flying into the unknown and figuring out how to make it work, while my
stores reflect our era, which benefits most from heeding the lessons they offer us.
We also encourage reading Wolfgang Langewiesche’s Introduction to the First
Edition , a few pages on, where you’ll find more of the story that led to this
book’s original core; with Mr. Langewiesche’s career and writings a fascinating
and learned endeavor well worth seeking.
It’s been about two generations since Weather Flying first came out, and since
then the pioneers and era from which it’s writings came are no longer with us.
With this, the needed old core is only available from disciples or the written word.
We hope this book’s original writings bring some of that written word, while the
new words link us to it. And these new words are not mine as claimed source;
instead I’m reporting the learning’s and lessons from countless clever folks in this
flying business. The sky is a wonderful and fascinating place, and we hope
Weather Flying is helpful companion to your hours aloft, treasured as much as
ours have been.
Acknowledgments
When you read my father’s comments in About Some People , you’ll have a
glimpse at some fascinating personalities who helped shape aviation. I’d like to
elaborate the story of Leighton Collins, to whom this book has always been
dedicated, and his magazine Air Facts . Leighton’s devotion to general aviation
and its safety, as well as his quality of aviation journalism, remains the high
standard for today. The magazine was written not only in-house, but also by most
anyone who wanted to contribute; a gift of forum for aviation. The diversity of
articles and range of knowledge for all aviation was phenomenal. Air Facts also
gave a foothold and encouragement to much of my father’s writing, which
ultimately led to Weather Flying , with four more titles after this one. Air Facts
also provided a home for the literary efforts of many young aviation enthusiasts,
including myself. Leighton Collins’ influence, for the industry and to me
personally, has been an immeasurable gift.
So, in switching generations, I thank Richard Collins, who’s encouragement
and helpful input toward revising Weather Flying were greatly appreciated, both
professionally and personally. I’d like to also recognize Richard’s devoted career
in general aviation, where he has mentored multiple generations and eras toward a
safer path. His skilled and experienced writings encourages us all to process the
important task of learning about weather and flying it carefully, especially as he
always has—a pro. And Air Facts is now back with us electronically, again of
superbly diverse content both in-house and from the enthusiasts, as
www.airfactsjournal.com .
In the beginning of the project, Jeff Newman offered helpful guidance that
brought me out of the cold as to the publishing world, as well as sage words
towards taking on the task of family scribe.
Archie Trammell, of airborne weather radar school fame, and longtime
aviation journalist from whom we’ve all been fortunate to learn, offered generous
support and data towards revising Weather Flying . While editor of Business and
Commercial Aviation Magazine , he was my boss and patient mentor as I served
as a technical editor.
George Larson, aviation journalist, pilot and long-experienced editor, whose
superb and diverse writings over decades has brought enthusiasm to so many of
us who love aviation, kindly offered sage words from both the literary and
personal ranks, as well as calming support during moments of angst.
Bruce Landsberg, President of the Aircraft Owners and Pilots Association
(AOPA) Foundation, shared his thoughts about revising the book in the context of
today’s diverse world of general aviation technology, operations, and safety
concerns. His constant concern and efforts towards general aviation is generously
devoted and important.
We’re indebted to John and Dick Roberti’s Vermont Flying Service, including
Steve Skinner—maintenance, and Wayne Chase—instructor, and all the gang of
aviators that make it a fine flying home. They have supported and made possible
our family flying for decades, even in cold Vermont winters. They, as well as their
wonderful parents Edmando and Mary, have offered input and support to four
editions of Weather Flying , and other family writings.
Einar Enevoldson offered valuable input on flight instrumentation, from his
wealth of aviation experience as engineer, NASA and industry test-pilot, recordholder and now as founder and chairman of The Perlan Project—high-altitude
sailplane program. His modest brilliance is a generous treasure to aviation.
Andy Nash, John Goff, and Eric Evenson of the National Weather Service
office in Burlington, Vermont, were an invaluable resource on wending through
today’s superb and extensive sources of weather information and application.
They also continued the kind tradition of NWS-Burlington offering invaluable
assistance to many family publications.
National Weather Service meteorologist Dan Gudgel, offered suggestions of
concept to this book’s direction, both personally and through his diverse writings
on weather and the National Weather Service in Soaring Magazine .
Steve Caisse shared his airline dispatching and meteorology expertise,
especially in an operational sense.
Meteorologists Steve Stock, Fred Brennan, and Erik Wildgrube offered
valuable insights on modern weather information dissemination and application.
Local Vermont meteorologist Roger Hill made available his broad reach of
weather knowledge, especially in the area of climatology. His website
(www.weatheringheights.com ) is an interesting and unique resource.
Dr. Ralph Markson, scientist and aviator, generously shared his long and
determined years of research on, among other phenomena, thunderstorms and
lightning, aiming me down a better path in offering the subject to you, the reader.
Dr. John Hansman, who brings to aeronautics a wonderful blend of academic
prowess and classic stick-and-rudder pilot skills, from sport aviation to flight test
and research, offered helpful insight into timely icing and weather data issues, as
well as related operational inputs.
Captain Douglas Smith, Delta Air Lines (retired), whose career-long
enthusiasm as aviator, flight instructor, and author has given his high-quality of
example to the new and seasoned pilot alike, found time to kindly share his
support and many valuable thoughts to this project. As founder of Vermont Flight
Academy, he made available their facilities and personnel to assist in revising
Weather Flying , including providing the simulator pictures, which Tyler Brown
organized and is our enthusiastic pilot at the desktop trainer.
Captain Monty Sullivan, Chief Pilot for Corning Incorporated, offered
valuable insights into the professional world of corporate aviation and its
operations, especially as to advanced aircraft and avionics.
Captain Steve Green, from his extensive involvement with aircraft icing
research, accident investigation, and operational awareness, offered helpful
updates regarding icing and related operational concerns, as well as generous
readings and critiques to portions of this work.
Captain David Kloss was especially helpful with instrumentation concepts and
operation, drawing on his engineering background as well as extensive
involvement with general aviation and airline flying, including years of
instructing. His reading of the text and sage comments were invaluable.
Captains Mark Shepard and Neil Muxworthy provided an opportune look at
advanced simulation and also offered helpful input to operational aspects of
today’s state of aircraft automation.
Longtime friend Bob Bowden, who defines the words “a natural pilot” and
thinks better and more sensibly about aviation than any of us, was continually
helpful in keeping this book’s revision in touch with core flying sense.
Captain Gordon Boettger, who shared his first-hand skills and knowledge with
high-altitude and long-distance wave-soaring. His picture, Looking North , which
he generously provided for the turbulence chapter, brings us the sky’s power and
beauty from a rare perspective.
Russell Kelsea, from his years of experience in general aviation, offered great
suggestions on merging automation and flying basics.
Paul Gaines, with his business of Composite Solutions, offered consult from
his extensive experience in composite aircraft repair and performance
enhancement, on current general aviation composite aircraft design and structures.
Of the National Soaring Museum in Elmira, New York, museum director Peter
Smith and marketing director Ron Ogden, assisted in archival research and
obtaining current copy of the Robert Symons Sierra Wave picture. The museum is
valuable resource and excellent display of soaring’s fascinating and important
history.
Dr. Graham Ramsden, good friend, professor, and fellow soaring enthusiast,
shared his academic suggestions on plodding through the project, including
tenacity of the effort.
Ryan Oshea gave valuable input, taking time to read part of the text and
offering his experienced input.
Kitty Werner helped immensely in various text and editorial tasks, as well as
continued a tradition by having assisted my father in his writing tasks.
Thank you, Ky Copeland, for always having the answer to my numerous
computer quandaries.
My appreciation to all the folks out there who I may have embarrassingly
missed or with whom I’ve shared this flying business, either in person or during
thousands of hours together in the sky. They have given their mentorship,
encouragement, hints, flat criticism, patience, professionalism, and yes, the great
wit and humor that permeate aviation. One is fortunate to share such a great
world, with memories that last for a lifetime.
I’m very thankful for McGraw-Hill Senior Editor Larry Hager, whose kind
soul encouraged keeping the book in the family and allowed my unpracticed
willingness to take on this project. Larry, along with his assistant Bridget
Thoreson, bore the brunt of my learning curve in this large writing task. Then,
finally, it was a pleasure working with Sheena Uprety and her team through copy
editing to the book’s production. I have to admit flying airplanes for a living is a
heck of a lot easier.
My wife Holly, daughter Heather, and sons Aaron, Todd, and Christian offered
support of task, suggestions, and patience as I orbited in moments of angst and
frustration. In the last throes of the project, Christian’s well-timed college
vacation and computer wizardry allowed him to bring illustrations into usable
format and helped firm up the text, as did Aaron’s reading through part of the
manuscript, his suggestions helpful from his honed writing talent.
My sister Ferris and her family were always supportive of my life in the
clouds, interested in where it was going next and understanding when it became
complex. Ferris also offered her fine input to the writing task, along with many
memories and reminders of our lives growing up around the aviation world.
To my folks, Bob and Jean Buck. We again remember this opportunity of
revising Weather Flying was because my father wrote it in the first place—his
words are the ones that make it valid. When drawn into aviation’s spell at a very
young age, my parents encouraged prudently, and supported kindly. My father
usually mentored subtly and in intriguing ways. My mother coped patiently while
I was a young teenager but well into solo flight, her boys wandering the skies, and
at times not without complex father and son issues. She was always center of
home and patience.
Robert O. Buck
Waterbury Center, Vermont
Introduction to the First Edition
What Captain Robert Buck says in Weather Flying has not been said before. Other
books explain how weather is made; this book explains how weather is flown.
We get to the field in the morning. Here is the weather: the map, the forecasts,
the sequence of current reports from many points, the winds aloft—the whole
package, prepared by experts. However deep our knowledge of meteorology may
be, we cannot hope to do better. For us as pilots, the question is: What do I do
with this? Go or no go? If go: go underneath the weather, or on top, or through?
Or go around it? Follow a railroad? File an instrument flight plan? Go right away?
Delay a couple of hours?
Those questions; they are the last of the real problems of flying. Everything
else has now been quite well mastered. The airplane itself now works: it handles
nicely (at least, those flown by the general public). It has climb to spare, and we
can usually find some level where the air is smooth. Noise and vibration are
subdued: we can stand long hours in a day and make big distances. Electronics
tell us where we are. Airports are plentiful and runways long. Engine failure is so
rare we now almost forget about it. Even the economics of flying are no longer so
forbidding. But the weather …
It is not often clearly impossible. When it is, we have no problem: back to the
hotel. On the contrary (as Captain Buck points out), the weather is normally
flyable. Again, no problem, or only easy ones. But every once in a while—
depending on season and part of the world—something is sitting out there that
worries us. If you fly far enough in a straight line, you’re likely to come up
against some problem weather that very day. How well we deal with those
situations determines how well the airplane works.
Too bold, and we cause emergencies and have accidents. Too timid, and we
destroy the utility of the airplane and let our skill as pilots atrophy. Then pretty
soon we have to be more timid still.
These weather decisions can be painful to make, because we don’t really
know how to go about making them. And we know we don’t know! We make
them often by a process which is a dumb, confused struggle between “guts” and
“judgment,” ambition and fear. How it comes out depends on how we felt that day
when we last had a good scare, whether the girlfriend is looking, or “This town is
full, there is a convention on, you can’t get a hotel room, let’s go.” Things like
that tip the balance. And so (in Buck’s words) we “drag the luggage back to
town,” often for no reasoned cause, or we “fling ourselves into the air,” often with
only a vague estimate of what’s ahead. Or else, more likely, we stand around for
another hour, look at the weather map some more, wait for the next weather
sequence to come on the teletype, and think, “I wish I could talk this over with
some really experienced friend.” That’s where Bob Buck comes in.
Experienced? We could consider 2,000 hours quite a respectable lot of time.
Buck has some 2,000 Atlantic crossings! And those are only half of his
experience. At this writing, Captain Buck’s log records well over 29,000 hours, all
types. He set his first record when he was 16, in a Pitcairn Mailwing, an opencockpit biplane. It was the Junior Transcontinental Record, New York to Los
Angeles, and “It didn’t amount to much—mostly just getting there.” He set
another record, for nonstop distance in light airplanes, in a 90-horsepower
Monocoupe, overnight from California to Ohio—his engine quit there. With the
same airplane he joined an expedition and searched the jungle of Yucatan for
Maya ruins. He joined TWA as a copilot at the time when the DC-2 was the Giant
Airliner, then the DC-3.
In those ships, between Pittsburgh and Newark, on a winter night, a pilot
could learn a lot about flying the weather. It was about the toughest weather flying
ever done. Instrument flying was new then. Radio aids and instruments were still
quite crude, airplanes comparable in performance to present-day private airplanes.
But the airlines flew almost the same weather as now. TWA had a milk run from
Kansas City to Newark that took all night and made nine stops, and some nights
all nine required an instrument approach.
TWA made Bob Buck a captain in two years. Then the war came, and the first
great surge of ocean flying, in four-engined land planes, under the aegis of Air
Transport Command. Buck became Assistant Director of Training for TWA’s
Intercontinental Division (which was part and parcel of Air Transport Command).
He checked people out on the DC-4s and on the ocean routes. Next, for four years,
he was the captain and manager of a special research project that TWA had taken
on for the Army Air Forces. He had a B-17 bomber (“Flying Fortress”) to himself
and a mission to seek out precisely the kind of weather that others stayed away
from—the kind that gave the most trouble. It started with research into snow static
—the kind you find best in Alaska. Icing research was added, then other things;
before long, he was carrying 14 different projects. To find enough weather that
was bad enough, Buck ranged from Alaska to Panama, out to Hawaii, to
Southeast Asia, and, once, clear around the world. He ended up doing outright
thunderstorm research. For this, they gave him a P-61 twin-engined fighter (the
“Black Widow”) with lots of radar and lots of structural strength. He flew
thunderstorms forward and backward, slow and fast, high and low. What was
inside the monsters? Could you get through without spilling your gyros? How
much did you dare slow up the airplane? What was the best way to keep control of
the airplane? How bad was lightning, hail, turbulence? It was one of the first
deliberate, systematic series of flights through thunderstorms ever undertaken.
Buck then went back on the line, but kept doing new flight research for the
military and the airlines both—on airborne radar and on low , low instrument
approaches. When the Instrument Landing System first came in, he was one of
those who had to figure out the best way to use it. Once he wanted to study
runway visibility in fog as it appears to a pilot breaking out of a low overcast. He
let himself be hoisted up into the overcast, hanging in a parachute harness from a
captive balloon. He likes to fly.
He likes that left-hand front seat of an airplane. At one time they made him
chief pilot of TWA. He found that the desk work interfered with flying, and he
quit and went back on the line as a captain. “The sky is my office,” he once wrote.
He was again tapped for the executive side of the company. TWA’s president at the
time talked to him about it and held out the prospect of a vice-presidency. Buck
said: “Mr. Burgess, there are only two jobs on this airline I would want—yours or
mine.”
He owns a high-performance sailplane, which he flies in cross-country
competition. He once made a private tour of Africa in a DC-3. He has been
around the world once sidewise—i.e., via both poles. He sits on various national
and international committees that deal with piloting, is active in the Air Line
Pilots Association, and acts as a consultant to manufacturers of airplanes and
electronics. But always, when you see him again, he is just back from Paris or
Bombay, with a cabinful of passengers riding behind him.
So that’s the man who now comes in, as we stand there studying the weather
map and debating what to do. He knows our problem. We are not engaged in an
academic exercise: We are making, or passing up, a serious commitment. As we
search the weather map, we are also searching our souls: Am I good enough for
this? Can I hack it? On paper, this weather situation can be dealt with by suchand-such a procedure. In reality, when the pressure comes on, will I get flustered
and panicky, so that I can’t do my best? Airplanes are flown in weather by real
people, and the pilots—we, ourselves—are part of the situation.
Buck himself has been through enough tense situations to—well, to write a
book. He’s seen fellows’ knuckles turn white on the controls—and maybe
sometimes his own. There are some interesting short passages in his book where
he touches on that side—panic control, self-control, the constructive use of the
imagination. You can keep an easy touch on the control, he says, even though
your knees are shaking. These passages will convey a little of the man who is
talking to us—his air of ease, cultivated by long self-training and mental
discipline. They will also give you the impression that he is your friend. It’s
interesting to note here some things he does not say. He does not bore us, for
example, with the phony good advice, “Don’t exceed your limitations …” We do
not know exactly what our limitations are. You don’t know the breaking strength
of a material until you have broken it. Nor do we know how tough this particular
weather situation will be to fly. That’s just our problem!
And he does not come at us with an advanced course in meteorology.
Certainly it helps, in flying the weather, to know some textbook meteorology, to
have clear concepts of the things we meet in the air: cold fronts and warm fronts,
cumulus clouds and thunderstorms, inversions, dewpoint and temperature, and
types of fog, the principal air masses in our part of the world. This knowledge
helps us understand the language of the weather-person and the meaning of the
weather map. And it helps us to recognize these weather phenomena when we
meet them. The nature of the brain is such that we see what we have seen before,
and what we have a name for. We are blind to things which have not been
properly introduced. People had fronts passing over them for thousands of years,
but nobody ever saw a front as front —i.e., as boundary between contrasting air
masses. Then, 50 years ago, the Norwegians first recognized the cold front ,
described it, and named it. Now everybody can plainly see many frontal passages
every year. In this sense, some descriptive meteorology helps the pilot fly the
weather. But with the pilot’s main problem—What do I do?— textbook
meteorology helps only little. And just because it helps so little, we are tempted to
give him more—more than he has any use for: to go deep into the question of how
weather is made. The coriolis force, the geostrophic wind, the latent heat of
condensation, the adiabatic lapse rate, frontogenesis and frontolysis. All that is a
fascinating look into God’s kitchen, but the pilot does not want to make the
weather—or even the forecast. All he wants to do is fly it. And for that he does not
need more meteorology; he needs a different kind, and he is getting it here.
What is it Captain Buck does for us? It’s like untying a knot. The bafflement
we feel as we try to judge a weather situation is a sort of knot in which everything
is balled together. Weather. He shows us where to find the place to start and how
to unravel it.
Read what he says about the big picture, the If-Thinking, and Way Out, and
right away the problem takes on order. These are indeed things on which we can
ask questions, find the information, and make judgment. Perspectives open, a
strategy suggests itself. More questions follow. What will be the influence of the
local terrain, the time of day? You feed that in, and you can make more
judgments. Now you have more to judge by: This mountain range is okay now but
probably will have many thunderstorms in the afternoon. Better go now. This city
with this wind direction will have industrial smoke in the morning, but visibility
will improve by noon; you gain by delay. And so on. By showing us what the
productive questions are, Captain Buck arms us with a judgment capability we
never knew we had.
Another problem that baffles us: how to monitor the weather once we are en
route. The weather here and now is okay. But where I’m going it is different, and
by the time I get there it will be different again. Is the situation solid? Should I do
something or just keep flying? How can I know?
Sure, we can get weather information by radio. But the same old problem:
What is the intelligent question to ask? And what do we do with the information?
Should we do anything? Many of us find it difficult to get an effective thought
process started. We just keep on flying and hope the weather will hold. Buck
reminds us that a whole weather system may not move as fast as “they” expect, or
may move faster or may even back up. This is perhaps the most frequent reason
for forecasts going sour. He thereby gives us another productive question to ask:
Is the weather system moving as expected?
Now that we see the question, we can often get the answer we need by
watching (for example, the progress of a cold front) at points that may be quite far
off to the side of our route. It’s really a quite simple idea. It’s just a sample the
captain gives us of what goes on in his mind when he is captain. But it greatly
smartens us up.
Bob Buck writes as he talks and flies, with an easy touch. He uses small
words. Unlike most professionals, he does not try to make his art seem mysterious
and difficult: He makes it seem simple and plain. This might fool some reader into
thinking that he is getting just a light chat. Not so. What we get here is in reality a
sophisticated course in problem solving. Buck shows us not what to think but how
to think. Not “What should I do?” but “How do I go about deciding what to do?”
Rules never quite fit the real-life situation. But a man who acts on rational
grounds and knows what his reasons are can deal with the variety of real-life
situations realistically. And should things not work out as expected, should the
judgments have been mistaken or the information false, such a man discovers his
error early, while he still can do something about it. Rational decision making: In
business or government, we call this the Harvard Business School Approach. It is
an American specialty, and it has been immensely productive. It will be
productive for readers of this book.
Because of this sophisticated approach, Bob Buck’s book is equally useful to
pilots of all experience levels. All pilots do not fly the same degree of weather.
Many people have to fly Visual Flight Rules (VFR); some fly instruments. Many
have to be cautious; some can fly tough. But all have much the same problem of
decision making—the problem the captain shows us how to solve. And so, this
book being about this sort of thing, and written by this sort of man, a pilot needs
an introduction to it like a hungry man needs an introduction to a steak. Just start
right in.
Wolfgang Langewiesche
Princeton, New Jersey
1970
1
Weather Flying
Weather bothers our flying in only a few basic ways: it prevents us from seeing; it
bounces us around to the extent that it may be difficult to keep the airplane under
control and in one piece; and ice, wind, or large temperature variations may
reduce the airplane’s performance to a serious degree.
That’s what weather does. There are degrees and nuances, but all in all, we
fight weather in order to see, keep the airplane under control, and to get the best
and safest performance from an aircraft. The question is, “How?”
Well, we should know something about weather, what it is made of, and how it
moves. But a pilot wants to know practical things: what to do about the weather
and how to cope with its capriciousness. These practical things are a philosophy
for thinking about weather and methods of flying it.
Prior to developing a philosophy and methods, a pilot should have one point
firmly etched in mind: weather forecasting is not an exact science. This statement
is an old one, but it’s true and ought to be thought about before tossing it aside as
old hat.
The best weatherperson or an impersonal computer cannot forecast with
perfect accuracy. The National Weather Service can make impressive statements
about how well they do, and their numbers are valid and true. In the overall
picture, they do a good job, percentage-wise; but the time they miss and pull their
accuracy down from 100 percent to something even a little less may happen to be
the night our destination was forecast clear, but fell on its face to zero-zero! Right
then, the pilot isn’t much interested in statistics—except in trying not to become
one.
This shouldn’t be taken as criticism of meteorologists or computers. Actually,
a compassionate, understanding, and friendly feeling toward them will do the
most good, but understand the cold fact: you cannot count on weather always
doing what is forecast, because even with fancy computer models, satellites, and
perhaps a little witchcraft, we simply cannot outguess it 100 percent of the time.
This means there will be times when the weather is not as forecast, when it will be
bad rather than good. This is a fact of flying life, and we must always be prepared
for it, accepting this as part of the game, ready to cope with it coolly and free of
emotion. And that is the most important statement in the book!
The pilot’s weather philosophy has two parts. The first is skepticism. Being a
weather skeptic is an important ingredient of the formula for living to a ripe old
age. The second part is always to have an alternate plan of action. These two
keys, skepticism and alternate action, are the foundation of it all.
Being a skeptic keeps us safe; having an alternate plan of action adds to
safety, but more importantly, it makes it possible to fly and to make the airplane
work.
If we are completely skeptical, we put the airplane in the hangar and forget
about it, and sometimes this is a good idea. But we are trying to use airplanes; we
want to go places as much as possible. The alternate plan of action helps us to do
so.
Say a pilot is headed for a place that’s forecast clear; skepticism says it’s near
the coast, night is approaching, the temperature is near the dewpoint, and the wind
from the sea—our destination airport could fog in. Now the easiest way out would
be to stay home. However, we can also take off and probably make it, as long as
there is enough fuel to get away from the coast, should it fog in, and fly back
inland to a fog-free airport. That’s alternate action.
That is a very simple example, but it is basic and important. It is the way
airlines operate and the way they keep going. They are skeptical about weather—
skeptical enough to have an alternate plan of action for everything they do.
To fly in weather, a pilot needs certain abilities and various degrees of
equipment. Since all pilots cannot have all the ability and all the equipment, they
must take on weather in amounts that fit their levels of ability and equipment.
This can be done, and the fact that a pilot doesn’t have instruments, radio, and a
rating to use them doesn’t mean he or she has to stay on the ground whenever
there is a cloud in the sky. However, it does mean that pilots must realize their
limitations.
There is a point of confusion in this area that gets people in trouble: the
mistaken idea that equipment makes up for lack of ability. A pilot can have an
airplane with all the trinkets, bright and new, up to par and working well, but if
that pilot doesn’t know how to use them, and how to go back and manage with
just basic instruments should the fancy stuff fail, that pilot is worse off than a pilot
with nothing more than engine instruments and a compass. These issues are
exponentially and dramatically magnified in today’s world of automation and
technically advanced aircrafts. Remember, despite the most sophisticated
equipment available, big airplane or small, it is not possible to fly all the weather
conditions Mother Nature can create!
What all this means is that pilots must know and fly by their limitations. All
pilots, even 40,000-hour professional pilots, have them.
What we are going to do in this book is talk about flying the weather. We will
talk about weather in the meteorological sense and then about how we approach
the weather problem and what to do about it. We will also talk about pilots’
emotions and thoughts when they find themselves, say, in the middle of a
thunderstorm.
There are things to talk about, such as instrument flying techniques and how
to test yourself to get an idea of your limitations. There are matters of technique
and philosophy for the person who doesn’t fly instruments.
One of aviation’s greatest fascinations is the weather. When it’s bad, it
consumes our flying thoughts, but we think about it, too, on a sunny, clear day
with a light wind and pleasant temperatures, if for no other reason than we must
say: “What a beautiful day to fly, but I wonder if it will stay this way.” Weather
has so many facets that we never stop learning about it. Personally, with more
than 80 years of combined flying, it has taught us for certain that one can never
definitely say that the situation is guaranteed, knowing exactly what will happen.
We learn to respect weather and never to be complacent about it.
This is the warm kind of respect we give to a beloved adversary, for after all,
weather gives us many things: green grass, a blue sky with fluffy white clouds,
and the rush of a summer storm that thrills and excites us. It gives the cool, soft
kiss of gently falling snow, and the beautiful following day when the front has
passed, offering gifts of sparkling sunshine and crisp, invigorating air.
Like a good friend, weather rarely bores us; it supplies constant variety for our
lives. How dull it would be, on the ground or in the air, if we never had to ask,
“What’s the weather going to be?”
2
A Little Theory for Weather Flying
Most books on weather start out by saying that air is made up of 21 percent
oxygen, 78 percent nitrogen, and 1 percent other gases. This isn’t that kind of
book, and instead we might say that air is made up of wind, turbulence, clouds,
precipitation, some fog, and a lot of nice, clear days. But we cannot escape all the
theory and must talk about some of it.
You will find lots of things said more than once in this book. This is because
many weather factors apply to more than one weather condition and will
automatically be repeated as different types of weather and flying are discussed.
And lots of points are purposely repeated to be extra sure we understand their
importance.
Weather is complicated. A deep study of the science shows many complex
factors, but when you boil it all down, the keys are temperature and moisture;
visible (precipitation or cloud) or invisible (vapor). Basically, there is always a
certain amount of water vapor in the air, and when air is cooled, this water vapor
is squeezed out and made visible. Much of meteorological study revolves around
the ways water vapor can bother us, and what processes there are to cool the air
enough to make that water vapor visible.
That Important Dewpoint
There are a couple of items that pilots should know. One is dewpoint. Most of us
know it as the temperature at which condensation begins. If the temperature is 15
degrees C 1 and the dewpoint is 13 degrees C, we have only to cool the air 2
degrees for the moisture to come out where we can see it … and if it’s fog, that’s
all we can see. Dewpoint is handy for a pilot. It’s on the weather sequence reports,
and it is a simple matter to look at the temperature-dewpoint pair and decide what
the chances are that they will come together. That is a matter of deduction and
common sense. If night is approaching, the temperature is going down; if there’s a
body of water, with a wind blowing from it toward the land, the dewpoint is going
to go up, giving the same effect as lowering temperature. If it’s early morning, it is
obvious that the sun will come up and heat the air, separating the temperature and
dewpoint.
A little warning, however: Sometimes fog doesn’t form until the sun comes
up. An airport may have the same dewpoint and temperature during a still night
and yet not fog in. Then, just as the sun is coming up and we think everything will
be okay, the airport goes zero-zero. The reason for this phenomenon is that
formation of fog requires some turbulence. We know that fog feels still, and one
would bet there wasn’t any turbulence, but there is enough to mix the air and give
the fog depth; if there were no turbulence, with the dewpoint and temperature the
same, we would only get dew on the grass (hence the name dewpoint), and not the
fog. As the sun rises, however, on the rare occasion when the air is dead still, there
is a delicate period when the air begins to stir, creating slight turbulence before its
heating is sufficient to raise the temperature. With this sensitive setup, fog may
form suddenly; it’s like the situation of ice not freezing in a bucket of water with
the temperature below freezing, until the water is disturbed.
Ground fog will generally burn off with heat from the sun. This burn off,
however, will take longer in winter, especially at high latitudes, and if there’s an
overcast above reducing the sun’s heat, the fog may never burn off. While stewing
on the ground waiting for ground fog to go away, we can contact weather sources,
either through electronic access or by calling the Flight Service Station (FSS),
looking for pilot reports (PIREPs) to see whether a higher overcast exists. If it
does, we’ll have a longer wait for the fog to dissipate.
If rain begins falling from a front, it will raise the dewpoint, and if night is
approaching, it will lower the temperature; thus, both temperature and dewpoint
are working to get together and make it a miserable evening. There are many
combinations that bring these two together, and in most cases it doesn’t take a
scientist to figure them out. The temperature–dewpoint relationship is a key guide
to weather flying, one which pilots should always keep right up front and current.
How Air Cools
We should also review how air gets cooler. The simplest way is by the sun going
down. As we discover at an early age, it gets cooler at night. This type of cooling
is called “cooling by radiation.” Another way to cool things is to bring colder air
into an area; a front goes by, the wind turns northwest, colder air flows in, and the
temperature drops. Cool air can also flow to the land from a body of water. This
process is called advection , and it can bring in or take away moisture.
The other cooling process is called adiabatic . This is simply a physical law
that says when air expands, it gets cooler. What makes it expand? Lifting. When
wind pushes air up a mountainside, it is lifting the air. It goes up the mountain to a
higher altitude, where the atmospheric pressure is lower. The expanding air cools
at a rate of 3 degrees C for each 1,000 feet it’s lifted (5.4 degrees F). If the air is
lifted high enough, it may cool to the dewpoint, and then a cloud forms.
It’s also important to note—that the opposite happens when air comes down a
mountainside. The pressure increases, the air gets warmer, the dew-point and
temperature separate, and clouds or fog dissipate. The entire process can often be
observed on a mountain. The windward side has a cloud near the mountaintop,
beginning partway up the slope and hugging the mountainside and mountaintop
with an eerie white cover. Then, on the downward side, we see the cloud shred off
and disappear, leaving the downwind mountain slope clear; lifting, cooling, and
condensing on the upwind side; descending, warming, and dissipating on the
downwind side.
We can sometimes see the same thing up high, when watching a lenticular
cloud downwind and away from the mountain where a wave has formed. As the
air flows up the front or windward side of the mountain, it continues upward well
beyond mountain height, and is the front side of what we call a “mountain wave.”
Like a mountain made of air, on this upwind side of the wave a cloud forms; then,
as the air flows down the other side of the wave, the cloud disappears. It’s a
fascinating cloud, because it doesn’t drift, it just sits in one place, forming and
dissipating. It is a smooth, curved cloud that we’ve observed when playing with
waves in a glider, often skimming close over the smooth, domed top of a brilliant
white “lennie,” as we commonly call lenticular clouds.
However, beware of flight under a lenticular cloud; that’s where the rotor is
located, and the air is very, very rough—more on that later. One can watch the
downwind edge of the cloud and see the motion as the pieces shred away and
disappear. All this, the flow up or down a mountainside or wave, allows us to see
the adiabatic process at work; lifting, reducing pressure, and cooling; lowering,
increasing pressure, and heating; making a cloud and then destroying it.
If the air being lifted up the mountain is unstable, the cloud does not dissipate;
instead, it keeps going upward and may turn into the type of thunderstorm we
would call orographic. That is the difference between stable and unstable air:
stable air comes back down when the force lifting it is removed; unstable air, once
it has been lifted to the point where clouds form, breaks loose from the lifting
force and keeps going up by itself.
Other things raise air and cool it. A cold front pushes warm air up, or air flows
up over cold air, becoming, of course, a warm front. And the reverse of nighttime
cooling is daytime heating, which makes air rise as thermals, the things glider
pilots look for, to circle in and go up. When this air cools to its dewpoint, we get
cumulus clouds, and if the air has a certain moisture content and is unstable, the
clouds grow into thunderstorms.
A meteorologist sees all these changes and additions, or subtractions, in a
sophisticated way, studying upper-air soundings and weather information from
many places and in many forms. A meteorologist is trained to study this mass of
information and analyze it quickly. Nowadays computers are doing most of that
task, but in some respects not as well. The computer lacks the local knowledge a
meteorologist develops by being stationed at one location for a long time,
knowing the little quirks of terrain, wind flow around it, and a host of other things
the computer doesn’t know. Many old-time instructors and fixed-base operators
(FBOs) have developed a good weather understanding of their areas, and a talk
with one of them about an airport’s weather, for future reference, can be
rewarding.
In a total meteorologist’s sense, we as individuals don’t have all the
sophisticated weather information, but with today’s computerized world we can
access quite a bit of it. However, even with this information, most of us will not
know what to do with it as a total meteorological analysis. We do, however, have
weather reports and digital imaging, which allows us to “see” what the weather is
doing. We can relate what we see and call it the “big weather picture.” We can ask
ourselves, simply: is it going to cool off and is there moisture present, either
coming in now, or possibly coming in later, to go with the cooling? By doing this,
it is possible to reduce all the complex weather factors to a simple understanding.
What makes a front potent? Warm air being cooled. What makes clouds on a
mountain? Warm air being cooled. What makes fog over a seaside airport? Wind
bringing in moisture or cooling the air. What makes fog in the country? Moist air
being cooled at night after the sun goes down. What makes low ceilings when it
rains? Rain falling into lower air, raising the dewpoint, and causing low stratus
and fog. We can go on and on, and finally relate any weather that restricts our
visibility to temperature and moisture.
Season and Time of Day
In our thinking of temperature and moisture, we should consider two important
points: season and time of day. In the summer, things are more phlegmatic, and
the weather is basically good, or it tries to be. In winter it is more violent and
moves and changes quickly. But fall and spring are the most difficult times to
predict. Air masses haven’t decided whether it’s winter or summer; temperatures
can be colder or warmer than expected and give unexpected bad weather. The
nights are not really long, but they are long enough to produce substantial
cooling. A spring day can be mild and docile, or it can blow and be wild.
All our weather thinking should be related to the time of day. We must simply
ask, is it the full part of the day when it is warm, or are we catching up with the
cool night, when temperature and dewpoint get together?
Terrain
Terrain is an important ingredient in weather. Terrain that rises presents a chance
for air to be lifted. Sometimes this rise in terrain—the orographic effect—can be
very abrupt and dramatic. A mountain range may suddenly burst upward from flat
ground, like the Rocky Mountains as one approaches Denver from the east, after
flying over miles and miles of flat land in eastern Colorado. On the other hand,
rising terrain can be subtle, like the gradual slope of the land from the Gulf of
Mexico’s Texas coast to the higher land in eastern Colorado. This rise sneaks up
on us and doesn’t clearly display itself, but the silent flow of warm, moist air up
this gentle slope can produce widespread fog or kick off thunderstorms.
Terrain makes bad weather worse. A cold front being pushed up a
mountainside is nastier than a front crossing Indiana, where the terrain is flat. Airmass thunderstorms are kicked off more quickly when wind flows up a
mountainside. Fog can form sooner in valleys where cold air collects. But to make
things more cheerful, mountains can help clear up weather on the downwind side,
where downflow heats the air and dissipates clouds or keeps ceilings up. This
effect often takes the clout out of cold fronts, making them more docile on the
downwind side of a mountain range.
Air can lose its moisture on the upwind side of mountains and be dry and clear
on the other side. A vivid example of this appears in the far West, where the
Pacific side of the mountain ranges gets a respectable annual rainfall and supports
plentiful vegetation, while the eastern side of these same mountains is a desert,
because most of the moisture is wrung out of the air on the western slopes.
To a pilot over Los Angeles encountering unexpected bad weather, there’s a
close escape by flying over the mountains to the desert, where the weather is
generally good. All this, in its way, is the adiabatic process at work, with terrain
helping it.
When we think of terrain, we should not think only of mountains and valleys,
but also of wide streams, lakes, and nearby oceans as well. Water and land
generally have different temperatures. In winter, the land is colder than the sea—
in summer, the reverse. We can see a demonstration of the temperature difference
between land and sea when flying through the Intertropical Front along the east
coast of South America. During the day the land gets hot, hotter than the sea, and
great towering thunderstorms are everywhere—except over the sea, where it’s
cooler. So, we fly out to sea in nice clear air. At night, however, the sea is warmer
than the land, and more and more showers are found offshore, so now we fly over
land for the best ride.
In winter, the lee of the Great Lakes has snow and stratus, because the wind
blows air across the lakes, where it picks up moisture. Then the air rises as it is
blown up the slope of the Allegheny Mountains. The result is zero-zero, with
snow and clouds on the mountains; the clouds are full of ice, and it takes 9,000 to
14,000 feet to get on top.
Cities are a part of terrain-weather thinking. Cities make smoke and pollution,
and those microscopic particles are something on which fog forms. Smoke and air
pollution make the formation of fog easier, and a wind carrying pollution toward
an airport is a setup for poor visibility. That’s terrain, human made, but still
terrain.
Wind
Another important factor in weather is wind, which plays a major role in a pilot’s
life. It affects us from the moment we take the airplane out of the hangar until we
secure it for the night. Wind tells us how we must handle an airplane on the
ground and during takeoff; it tells us how we must think and act while flying close
to uneven terrain; it tells us how short we can take off and land and what up and
downdrafts we can expect. Wind affects the performance of our airplane. A big jet
weighing 290,000 pounds can take off from a certain runway in calm conditions;
a 10-knot headwind can increase the gross to 300,000 pounds, but with a 5-knot
tailwind, the gross is reduced to 280,000 pounds. The same rules apply for a
Cessna 172 too; only the numbers are different.
Wind is also important when thinking about large-scale weather. First, on a
weather map we notice, almost automatically, that if the isobars are jammed
together like tracks in a railroad yard, it tells us the wind will be strong, or if they
are wide apart, the wind will be lazy.
Then we look at direction. East winds may bring bad weather, west winds
sunshine. Wind from a sea such as the Gulf of Mexico brings moisture that can
create bad weather. Knowing what the wind is, or catching its changes in velocity
or direction, can give us good weather clues.
Wind is layered and blows differently aloft than it does on the ground. The
wind up high tells a pilot about speed for a trip, and therefore, the required fuel
and reserves. Wind just above the ground, within the first 1,000 feet, tells about
shear and its hazards during takeoff and landing. While the wind may be calm on
the ground, especially true in valleys and at night, it can be blasting along at high
speed only a few hundred feet above the ground, which can be devastating to a
climb rate as you suddenly fly into an unexpected tailwind. Part of preflight
weather gathering should be a close inspection of the gradient wind; the wind
above the surface out of the earth’s friction layer. (Another term for this is PBL,
which means planetary boundary layer; a fancy name for what we’ve always
called the friction layer.)
The tremendous force of wind drove this board (measuring 10 feet × 3 inches × 1
inch) through a palm tree in Puerto Rico during a hurricane. (NOAA PHOTO)
An important part of wind action is convergence or, more simply, places
where winds from opposite directions bang into each other and pile up. The idea
of convergence and what happens because of it is difficult to pinpoint, and the
actions it causes are complicated. A convergence area can be very big, like the
Intertropical Front, also know as the Intertropical Convergence Zone (ITCZ),
where northeast trade winds run into southeast trades and create an area of large
cumulus and thunderstorms. Convergence can also be tiny, where a sea breeze
meets inland air and forms a miniature front of no special consequence, except for
a line of clouds a little way in from a coastline. These are called sea breeze fronts
and generally are mild, but just to keep alive the realization that weather’s ability
can surprise us, thunderstorms occasionally will develop along such fronts. Fronts
are a demonstration of convergence, and so are low-pressure areas. The important
point is that almost any time convergence is present, there will be some sort of
weather associated with it, because of the process of air being lifted and cooled.
Divergence is the opposite of convergence. Air flows down and away, which
again, in going back to the adiabatic process, heats up and generally gives good
weather. A high-pressure area is a large-scale divergence, a mass of sinking air.
This sinking air in a high, and the rising air in a low, affect flight more than we
realize.
When I (RNB) began flying the first 747s in 1970, a flight plan filed from
New York’s JFK to Europe made it important to note whether we would be
climbing through a high or low pressure area. That would determine what altitude
to file with Air Traffic Control (ATC) for crossing Nantucket, a checkpoint about
176 miles from JFK. If climbing in a low, the airplane could reach 33,000 feet,
because the converging, rising air would help the climb. However, climbing
through a high, with its diverging and settling air, the climb would be slower, with
29,000 feet at Nantucket. About all those early, low-powered versions of the
airplane could comfortably handle.
The biggest convergence zone: the Intertropical Front, shown in this satellite
picture. Thunderstorms show on South America’s northwest coast westward into
the Pacific. It’s less active eastward until the central South Atlantic toward Africa.
This is temporary as it strengthens and weakens because of activity or time of day.
If you fly between the Northern and Southern Hemispheres, you will have to cross
this area and its big thunderstorms—tops into the 60,000-foot range—and heavy
rains. (NOAA IMAGE)
Of course this effect works on any airplane. No doubt many pilots—especially
those flying small, lower-powered aircraft cross-country in a fresh high-pressure
area—have noticed how the airplane seemed to fly somewhat slower and worked
harder to keep normal cruising speed. This is even worse in mountainous regions,
but that’s for another reason—waves—which we’ll talk about later in the chapter
on turbulence.
A good pilot is wind conscious, aware of its direction and velocity, knowing
how it smells and feels, sensitive to a warm, humid wind or a crisp, cold one,
where it came from, and what kind of weather it will bring. A good pilot awakes
in the morning, looks out the window, sees where the surface wind is coming
from, looks up at the clouds, checks which way they are drifting, and learns the
wind aloft. All through the day, that pilot is subconsciously aware of the wind, and
if it changes, they sense it, then contemplates what this may mean. Any weatherwise pilot puts the wind and flying together, visualizing it tumbling over trees or
buildings near the approach end of a runway and what that will do to the airplane.
Our pilot tries to “see” the downdraft on a sharp mountainside and relates wind to
aircraft performance, as well as to the weather. The good pilot is animal-like in
sensitivity to the wind, feeling and understanding its motions by instinct.
Clouds
A pilot literally looks at the weather to see what it’s up to. One of the main things
observed is clouds. They tell a big story.
There are two cloud types, cumulus and stratus, and all cloud designations are
some combination of them. There are three classifications: cirrus, nimbus, and
alto. Cirrus are high-altitude clouds, and because they occur in high, cold air, they
are made of ice crystals; but they still follow the cumulus and stratus designations.
Nimbus is simply a name given to clouds when precipitation starts to come from
them—like cumulonimbus and nimbostratus. Alto simply designates height; it
means a cloud is at medium height, somewhere between 7,000 and 25,000 feet,
and again it is used with the basic cloud forms, as altostratus, altocumulus. You
never hear “altocirrus,” because cirrus by itself is high.
The important part about the two basic cloud types is their action and this, in
turn, tells how they were made. Cumulus clouds are bouncy clouds. They were
born of instability, born in air that once it starts up, wants to keep on going—for
that’s all instability is. Stratus clouds are smooth and flat, or almost flat; their air
is basically stable.
Heavy precipitation comes from unstable clouds; steady, light rain or drizzle,
comes from stable clouds. Said another way, ceilings and visibilities will be high
enough to land during unstable conditions, except we may briefly have heavy rain
or snow showers, causing the visibility to be near zero, the runway slick from rain
or even flooded, with stopping difficult. Precipitation from stable clouds means
low ceilings. Light precipitation can bring zero ceiling, or near it, with the
condition widespread and of long duration.
So fluffy white clouds are cumulus, and flat, layered ones are stratus. To make
it more confusing, they can be in combinations, as stratocumulus, for instance,
which is a layer of clouds containing some instability. The precipitation from the
clouds of slight instability can be light.
The stories clouds tell are varied. Cumulus clouds are generally thought of as
pretty, fluffy white things floating in a blue sky. They mean good weather. But
they are not all the same. We know that any cumulus-decorated sky will have
choppy air underneath the clouds and smooth air on top. If we look at the clouds
more closely, we can get an idea of how choppy it will be underneath. If the
clouds have a shredded look, like cotton that’s been pulled apart, it’s probably
rough; you are slapped around the sky, and it’s a good bet that the surface winds
are strong and gusty. When we fly gliders in these conditions, the rising thermals
are generally chopped up and difficult to stay in.
If, however, cumulus clouds are bulbous and fat, the choppy air will not be so
choppy, and the up and downdrafts will be better defined. You rise and descend
more like a boat in swells at sea. We also look at these fat cumulus clouds with
more suspicion, because they are the kind that may grow large and turn into
thunderstorms.
We can tell without even looking at a weather map, merely from the type of
cumulus present, a lot about the synoptic situation. The first type, the shredded
kind, are in an air mass that’s close behind a low, and a front has gone by with
fresh, vigorous air flowing into the area. We’re in for a few days of good weather.
The fat cumulus clouds say that we are deeper into a high, perhaps on the back
side of it, and warmer unstable air is coming in. Somewhere to the west a cold
front is probably starting our way.
Stratus clouds tell a different yarn. We may be flying in a mountainous area,
such as the New England states. There is a high overcast made of altostratus; the
visibility is good. Our destination, in the mountains farther south, is reporting
8,000 feet and 5 miles visibility with light rain—good enough. We know there’s a
rain area, a warm front approaching, but the forecasts do not make our destination
really bad until long after our arrival. We fly on and notice rain on our
windshield. The visibility drops some, but there’s enough. We are happy, even
though it rains a little harder. But then, looking down in a valley, we see a wisp of
stratus below, just a little thin glob of cloud floating along by itself. That should
be a red flare signal! Things are happening; enough rain has fallen into the lower
air to raise its dewpoint, and stratus is forming; stratus is the cloud low ceilings
are made of. It’s forming faster than the forecasts indicate; the next thing we know
our destination will have about a 300-foot ceiling or less. We review our fuel,
check the alternate and destination weather, which is going down, and wish we
could hurry and get there before it socks in. All this was told to us by a little piece
of stratus.
Three layers of clouds and the stories they tell. Looking south, from 32,000 feet,
we are flying west. We’ve passed through the jet stream, under which is a cold
front—we’re on the back side, the front moving east. Up high is cirrus cloud, the
thick band from the jet stream: it was flowing from 221° at 155 knots. Below the
jet stream is an altostratus deck, around 20,000 foot. Down low and left is the
front’s back and cumulonimbus clouds. To right and behind the front are typical
post frontal cumulus and stratocumulus cloud, with average tops about 12,000
feet. It’s November, so maybe there’s ice in the cumulus. Position: mid-ocean,
North Atlantic—50° north and 40° west at 1649Z, November 10, 2005. (PHOTO
BY ROBERT O. BUCK)
We are flying westward on a summer day, on top in clear air with excellent
visibility; below, it’s hazy and difficult to see. Way west of us there’s a cold front,
which is forecast to arrive at our destination long after we do. But suddenly our
eye catches a different shading in the high sky far ahead. We take off our
sunglasses to see it better, but we can’t; we put them on and squint a little, trying
to pick it out. We fly on and look some more. Then we’re certain. The western sky
holds solid cirrus, white and innocent looking, but it’s a sign that says let’s check
that front; it may be moving faster than we thought, or a pre-frontal line squall
may be developing.
These are a few examples of the many things clouds tell us; they are an entire
weather story placed in the sky for us to read. We can study for a long time and
never know the whole story, but it is profitable and interesting to try.
1 . Because weather reports (METAR) now use Celsius (C), we’ll do the same,
with an occasional reference to Fahrenheit (F) just for old times’ sake.
3
Some Thoughts on Checking Weather
Weather is fickle enough to justify checking it prior to any flight. Even when
shooting touch and goes at the local airport on a lovely Visual Flight Rules (VFR)
day, information on wind changes, some precipitation beginning, or other weather
issues can be valuable.
Having weather and forecast knowledge cuts down on alarming surprises or
can reward us with some great flying that might otherwise be missed, because we
didn’t understand weather well enough to see through the questionable sky. Being
inquisitive about weather must be part of our flying character, because it creates
an awareness that is necessary even when one’s log book shows thousands of
hours. It comes down to the fact that the moment a person says, “I’m going to
learn to fly,” that person needs to add, “and I’ll learn weather, too.” Flying and
weather should be thought of as one skill, one art, never separated. Anytime we
fly, weather is part of the game, and the pilot, regardless of mission, should know
what the weather is, what it’s supposed to do, and have safe alternatives if it turns
sour. We must always be aware, on every flight, that safety is our goal and
weather the adversary.
It Isn’t Easy
Now where and how do we get this weather information? It isn’t always easy, and
there are times we may takeoff feeling the necessary weather questions are not
clearly defined. Despite all the available information, today’s systems still leave
the weather decisions and their burden firmly on the pilot, a fact that isn’t always
recognized.
Weather information comes from a plethora of services. The most important—
and official—weather information still comes from telephoning the Flight Service
Station (FSS ), [also referred to as Automated Flight Service Station (AFSS ), but
we’ll use FSS throughout the book], which is overseen by the Federal Aviation
Administration (FAA). For those who desire computerized self-briefing, one of
the two FAA-approved weather websites—Direct User Access Terminal Systems
(DUATS ) or Direct User Access Terminal (DUAT )—also makes sure we have
this same accurate foundation of basic weather information. We can also file our
flight plans through their services.
Away from the FSS or DUATS/DUAT, there are other weather briefing and
flight planning sources, many of which source through personal electronic device
applications. A lot of them are excellent, with some providing their information
in-flight, through data-linking of everything from maps and approach charts to
navigation and weather data. Another source comes from high-end commercial
facilitators that offer weather and flight planning services, as well as fuel, lodging,
food, and more. Probably everyone, at various times, watches TV weather for a
look and study of weather’s general setup—the synopsis—but it is important to
realize this is something from which we gain a general plan of the weather picture,
and should not use it as detailed weather information for flight.
Self-briefings have opened a whole new dimension in flight planning. The
quantity of information is extensive, but with its nature of presentation by
computer, requires the user to evaluate the information as a lone entity, one who,
for most of us, is not a trained weather professional. We need to fathom that
weather data is not just information; instead, it requires understanding of not only
what it says, but also what it means and what to do with it. We must weave this
task precisely and accurately, not on assumption. Only then is it useful to safe
flight planning. Weather information should never sway us to accept it passively;
a knowledgeable, constant evaluation–decision process is necessary.
Weather is one of those things about which we learn basics, but the knowledge
is best honed with face-to-face mentorship and subsequent verification by flying
experience, done within the limits of our weather knowledge. This is especially
important when we are new and unfamiliar with the subject. However, an irony
exists in that the task of deciphering weather information has been placed in the
lap of pilots with greater magnitude than ever before, but at the same time with
arguably less mentor-ship, than aviation has ever experienced. The explanation of
this issue is a story we feel worth telling.
Back in the late 1920s, the United States Weather Bureau (USWB ), now the
National Weather Service (NWS ), was given the task of supplying weather
information to the budding aviation industry. By the 1950s, a partnership evolved
between the Weather Bureau and FAA by bringing aviation weather and pilot
briefings to the new FSS system. Often, the facilities were co-located in the same
building; if not, you could brief at either one and call the other. The FSS
briefers/specialists* were well trained on providing the now standard weather
briefing format, using approved weather information from sources like their
neighbors at the NWS and other government weather-related agencies.
Conversely, NWS meteorologists were trained to use their meteorological
expertise in aviation-related weather briefings. FSS briefers also handled other
functions, such as air–ground weather information, airport advisory for
uncontrolled airports, flight planning, and helping distressed aircraft. Most FSS
briefers were not meteorologists, but they developed a lot of helpful local weather
knowledge. Supposedly, they were not to use this, but they did off-the-cuff, and it
was usually very helpful. Next door at the Weather Bureau, a pilot could get a
meteorologist’s sage knowledge of the weather; they dug into some real nitty-
gritty, explained it to you, and when you were ready to fly, your grasp of sky was
pretty good. Not only could we telephone these facilities, but we could also walk
in and have excellent face-to-face weather briefings at the FSS and/or NWS
facilities. As said in this book’s 1996 edition: “There is nothing better than a
human to talk to, ask questions of, and get the picture we need of what’s out there
and how it is going to behave.” The real jewel of this whole deal was that we
learned a heck of a lot from those personal visits, not only about weather and
flight, but also about prescribing sensible limits to weather flying.
What happened? The FSS system became the primary source for all pilot
briefings, and eventually it was decreed that the NWSs would no longer give pilot
weather briefings. During the peak years of the local FSS system, in the early
1970s, there where nearly 400 airport-located facilities nationwide, making it very
likely most flying trips had some opportunity for face to face weather briefings,
and all they offered in thorough weather analysis, as well as assistance to the less
savvy weather pilot. Then, by the later 1990s, with computerized weather data
coming up to speed, political powers and budgeting began consolidating the local
FSSs, and today, in the lower 48 United States, there are three main centralized
facilities, plus as of this writing, three other augmenting facilities which assist the
work load of the “big three” centralized FSSs. An exception is in Alaska, where a
system of multiple, local FSS stations remains, which is a smart move for that
areas demanding weather flying environment. Also, many of the 120 or so NWS
offices began relocating away from airports, and today not all are accessible 24/7,
whether by telephone or walk-in. So has ended the era of walk-in briefings at
FSSs and many NWS offices. The big loss, in our view, was the mentoring that
went with it; especially helpful to the new or not too weather-savvy pilot, let
alone experienced ones who were old-school smart and respected a good briefer
or meteorologist’s input. And this is why we believe the modern pilot needs to
understand weather, and its application to aviation, more than ever before.
So what is left? Fortunately, the centralized FSSs gives us reliable, consistent
weather briefings and in-flight weather data, along with flight plans, assisting
distressed aircraft, and so on, through telephone or radio contact with a real
human being, the FAA briefer/specialist, and the next best thing to face-to-face
contact. Actually, there was originally a bit of a challenge with FSS centralization,
as the FSS briefer we’d talk with was the first available one who answered the
nationwide phone system; such as chatting with someone on the East Coast, and
the familiarity with briefing that area while we were flying in, say, California. The
FSS briefers were stuck with that as much as pilots were, but at the same time
they’re professional attitude worked hard to fulfill our needs. Today’s FSS system
has improved, doing a good job in matching FSS briefers familiar with areas we
are flying; that’s why the current phone system asks what state we are flying from.
Actually, many FSS briefers/ specialists are general aviation pilots, enhancing
their understanding of the important pilot-weather interface. With FSS
communication being human, it is not as fast as our own view on a computer or
personal electronic device, so may take a bit longer. However, this trade-off gives
us the latitude of human contact, and the briefer’s trained expertise, versus a
computer’s pragmatic inability to question and discuss. So with a little patience,
phone contact uses the system as it has successfully worked for decades. Maybe
our impatience is a by-product of the times. Never the less, whether we get our
weather from the FSS or a computer, the task is still the same; the pilot must
ultimately understand, apply and make decisions from the data, allowing a safe
flight.
And the NWS meteorologist? The NWSs can be reached, depending on how
proactive we find each office. If we do reach an NWS meteorologist—either by
phone or walk-in—while they do not give aviation briefings, they are free to give
an opinion of the weather. Usually, they are quite helpful and concerned about our
needs. It is worth making an effort to call (their contact numbers are accessed
through the NWS website), as well as visit an NWS office, as it is a great learning
experience.
On the other hand, if we decide not to call the FSS or NWS and are using the
very popular computerized weather, we need to have that well-studied
understanding of all this weather business, especially what we should have as a
minimum for an appropriate weather briefing. With that thought, how many pilots,
either new or well experienced, can always say they are on par with well trained
weather personnel who immerse themselves in it everyday, solely for our benefit?
In a final thought, there are quite a few pilots who feel computer weather is
plenty adequate, and that the system could alleviate the FSS human briefing all
together, being instead totally dependant on computer-only weather data and flight
planning. Of those who feel this way, how many forget they came into aviation in
an era where we had face-to-face FSS and NWS briefings, or learned from spoonfed airline or military environments–with superbly equipped and performing
aircraft that can handle weather far better than most general aviation operations?
By going solely with computer weather, where do aviation’s new pilots find
mentorship as was afforded for many of us in years past? And we consider the
inability to get computer access, for whatever reasons, were a quick phone call
can save the day. If the aviation industry goes this way, it risks creating a whole
generation unaware of how delicate and important is the weather-aviation
relationship, and how to orchestrate it. A century of honed understanding, shot.
Then, how many accidents, rules, and restrictions later before we have to reinvent
the wheel of aviation and weather; if there is still someone around who
understands it?
It’s Approved and Official
A very important point is the difference between getting any sort of weather
information versus approved weather information. The official government term
for this is “Primary Weather Product.” These forecasts, actual weather reports,
adverse weather statements and warnings, wind products, synoptic analyses, and
airman notices are approved by the FAA in conjunction with the NWS and other
governmental weather facilities. They are deemed worthy of the regulatory and
safety needs, necessary and suitable, for aviation weather decisions and flight
planning. When we get a weather briefing from the FSS, or DUATS/DUAT, as
well as flight-planning services that reference these same methods and are
approved accordingly, it is not only of Primary Weather Products but also
packaged into a briefing format called a “Standard Briefing.” This guarantees we
get full coverage of adequate data needed for safely planning a flight. The briefing
also puts us on record as receiving this data, which basically covers us if there is
an incident where, no doubt, the FAA will want to know if we received a full
weather briefing.
So when we stray from an FSS or DUATS/DUAT briefing format, we are best
to know what we’re looking for and also realize we are not on record as receiving
an adequate pilot weather briefing. The Standard Briefing looks at its data for
complete coverage over the whole route of the flight. Below is a short list of the
weather-related criteria of the Standard Briefing:
•
•
•
•
•
•
•
Adverse conditions
Synopsis
Current conditions
En route forecast
Destination forecast
Winds and temperatures aloft
Notices to airmen (NOTAMS)
We can find a guide to weather products considered primary, fulfilling most of
the above criteria, through the NWS Aviation Weather Center (AWC) website.
But wait—that’s not all! If we have already briefed a flight, yet want a final
check of things before takeoff, we call the FSS and ask for an “Abbreviated
Briefing” that updates things without another long Standard Briefing. On the other
hand, if we are more than six hours before a planned flight and want a look at the
weather toward what to expect or whether we’ll go at all, the FSS offers an
“Outlook Briefing.”
Then there is also weather information the FAA calls Supplementary Weather
Products. These are weather offerings that by definition offer enhanced situational
awareness of the whole weather picture. This is very important to understand, as
many of these products are the most user friendly and enticing of all weather
products; primary or supplementary. They offer excellent graphical displays,
giving layered and sometimes profile views of icing, turbulence, thunderstorm
activity, temperatures, winds and cloud cover. They can tempt us to accept them
as primary data, but they are experimental and remain as supplements to Primary
data. For a concise explanation of Primary and Supplementary products, the
FAA’s book Aviation Weather Services AC 00-45G (version G as of this writing)
outlines the whole system.
Lastly, once airborne, we continue sourcing Primary Weather Products
through the FSS system. Using radio, we either contact the FSS directly or use the
excellent En Route Flight Advisory Service (EFAS ), also known as Flight Watch .
If we’re fortunate to have electronic flight instruments allowing data-link weather,
we can have the data on a snazzy display, right in front of us.
So we can see that years back, we lowly pilots didn’t worry about official or
legal weather information. It came in standard form from these FSS and NWS
professionals. They had what was needed, and walked us through those nuptial
years of our relationship between aviation and weather. Now, a lot more is up to
us.
How It Works
So a scenario might be something like this: We’re going from Burlington,
Vermont, to Morristown, New Jersey. We can call the FSS folks by phone,
requesting a full “Standard Briefing.” There is also that choice of self-briefing
through DUATS/DUAT, whether from a computer or through their application on
personal electronic devices. Another slant is to access one of the popular flightplanning applications, also self-briefing. In this example, however, we usually go
through the self-briefing, study it, then print it out, and finally call the FSS for a
“Standard Briefing.” This way we have heads-up to all the data, which helps us
process and picture the FSS briefers’ spoken weather data; this comes up again in
subsequent chapters. Again, with the FSS briefer, we have that chance to ask
questions and know we’ve covered the minimum data necessary. We’ve also
checked some of those Supplemental Weather Products, in this case allowing us a
“forecast” picture of possible icing, turbulence, and thunderstorm potential. Also,
our destination of Morristown does not issue a Terminal Aerodrome Forecast
(TAF), only an Aviation Routine Weather Report (METAR). So we cover this lack
of a Morristown TAF by looking closely at the Area Forecast (FA) covering New
Jersey, which gives us an idea of conditions during our arrival. We also call up
two nearby New Jersey airports that have published forecasts, Newark and
Teterboro. However, these two TAFs are only reference, as the area of TAF
validity only covers a five statute mile radius from an airport’s center.
This process verifies both weather and other flying information, including the
NOTAMs, SIGMETs, AIRMETS, and PIREPs. 1 To really verify the weather,
especially if it is a real challenging day that leaves us feeling a bit uncertain after
the briefing, we can call or, if possible, visit the local NWS office and chat with a
meteorologist. This is where we ask their idea of the weather in the Morristown
area, what the weather will be like from Vermont down through the Hudson River
Valley into New York and New Jersey, and how confident they are about the
prognostications. That gives a better feel for the weather and completes an
excellent briefing.
What we do with all this information remains the same as it has always been.
The key to keep in mind is that a preflight briefing is just what it says: before the
flight. Once the wheels leave the ground, the ball game changes. Then it becomes
the serious task of keeping up with the weather, watching to see if it’s doing what
the forecast said or not. “Not” is the important word and emphasizes the need for
being prepared to handle the situation a “busted” forecast will confront us with;
go to alternate, turn around, climb, descend, whatever.
Weather can change very quickly, and in no way does the currency of
information before takeoff relieve us of the responsibility of keeping an eye on
what’s going on, watching for weather’s periodic fickle actions.
A very important point about all this slick weather information is that it is still
weather with all its faults. The clipped, official look that electronic access and
airborne data link gives us doesn’t relieve the pilot one iota from watching how it
goes, being cautiously cynical about forecasts, and having alternate action well
thought out and provided for—this is very important.
Another important part of any weather briefing is the “IF” information: if it
doesn’t do this, it may do that. This is the kind of information we always got when
talking face-to-face with a meteorologist, leaning over a weather map, absorbing
the picture of lows, highs, fronts, and the rest. To show how this “IF” information
works, read this forecast issued:
SYNOPSIS VALID UNTIL 270400
AT 10Z LOW PRES CNTRD OVER THE CAROLINA CSTL WTRS. WILL
MOVE NWD DURING PD. 00Z LOW CNTR LCTD IN NEW ENG CSTL
WTRS. RMNDR PD LOW WILL MOVE NEWD.
[At 10Z low pressure centered over the Carolina coastal waters will move
northward during the period. By 00Z low center is located in New England
Coastal waters. Remainder of the period the low will move northeastward.]
In addition to the synoptic, note the area forecast for New Jersey:
NJ
CIGS BLO 10 OVC VSBYS BLO 3SW. CLD TOPS ARND 160.
ARND 17Z BCMG 15-25 OVC VSBYS 3-5SW. OTLK … MVFR CIG.
[New Jersey: Ceilings below 1,000 feet overcast with visibilities below 3
miles in snow showers. Cloud tops around 16,000 feet. Around 17Z becoming
1,500–2,500 overcast with visibilities 3 to 5 miles in snow showers. Outlook
is for Marginal VFR due to ceilings.]
So our grasp of this situation is that a flight into the New Jersey–New York
metropolitan area will have low clouds, but, as we learned from the New Jersey
forecast, quite flyable after 17Z, because the real nasty stuff will be tracking off to
the northeast. Of course that might affect our flight en route, so we’ll be checking
that carefully.
Gradual improvement is what it’s saying, because the low will move off to the
northeast. However, lows tracking along the coast often have a sneaky way of
sliding north, up the Hudson River Valley, slowing down, even stalling, and
leaving the weather poor and marginal much longer than forecast. Also, with snow
showers in the data, if in the clouds on an IFR (Instrument Flight Rules) flight, the
possibility of ice comes to mind.
If available, we should also check satellite weather, giving us an idea of cloud
cover, and NEXRAD (radar), for convective clouds, even if low-level winter stuff
that are not thunderstorms; the radar is, after all, showing precipitation. However,
the satellite picture is not for interrupting cloud bases, so we also take a look at the
Weather Depiction Chart, as well as Supplemental Weather Product of graphical
forecasts for ceilings, icing, convection and turbulence.
Ultimately, we need to remember that fronts, lows, highs, and other weather
can move differently than forecast, and pilots need be alert to this fact. But what
do we do about it?
You Are the Meteorologist
Chances were, in the good old days, if we talked to a meteorologist, they would
tell you how confident they were about the movement of that low pressure or
some other forecast situation. So getting ready for takeoff, we not only knew what
the weather was likely to be, but also that a suspicious eye should be kept on the
development, making sure that low pressure, or whatever phenomenon, didn’t
change its mind. In our present age, however, the weather information we may
have written down or seen on an electronic display has no “IF” information, so
we have to assume the role. Be that meteorologist.
Today, the pilot should be weather-wise enough to know when to be wary of a
setup and that it is necessary to keep an eye on it. In the TAF format, there’s a hint
of the forecaster’s confidence when you see a statement such as: “PROB30
0120/0122.” Decoded, this says there is a 30 percent chance between 2000Z and
2200Z on the first of the month of something possibly changing—for example,
snow showers, visibility lowering, and so on. A percentage like that in the forecast
should make us a little more wary, because it admits that a variable exists that the
meteorologists are not dead certain about. On the other hand, if there is a better
than a 50 percent chance of that something occurring, the statement in a TAF may
say “TEMPO 2812/2816,” meaning the phenomenon may be temporary. That
temporary weather is part of the whole weather forecast that encompasses either
side of the temporary time frame; the worse weather is that which governs our
decisions. A little more complex, we offer an example that is part of a forecast:
2812/2912 03005KT P6SM OVC012
TEMPO 2812/2816 4SM -DZ BR OVC008
[The forecast is valid between the 28th of a month at 1200Z until the 29th
at 1200Z. In that time, the wind will be from 030° at 5 knots, with visibility
greater than 6 statute miles, with an overcast at 1,200 feet. However, between
the 28th at 1200Z until 1600Z, the weather has better than a 50% chance of
dropping to a visibility of 4 statute miles in light drizzle and mist, with an
overcast at 800 feet.]
The deal here is that we have to flight plan for the lower temporary weather;
which just happens to bring Marginal Visual Flight Rules (MVFR ) conditions to
IFR , because the clouds are a ceiling, and it is below 1,000 feet.
As we see, these conditions of probability and temporary are just two
examples of science’s complex but fascinating mechanisms. To be good, safe
pilots, we should address these challenges with that study of weather—
meteorology. Also, we again emphasize this basic importance as being so relevant
today, with weather information and briefings coming from automated,
impersonal presentations. There are many excellent books and other sources that
go into the science and make it painless and interesting. We have quite a few listed
in the Suggested Reading section. Historically, however, the study of weather has
been hard to sell, even to very active pilots, and possibly this issue would make a
fine thesis from psychological study. Maybe it’s the science, possibly weather’s
pragmatic nature, or maybe it’s complexity comes to some as something far too
abstract; or annoying. Who knows? But the study of weather isn’t all that bad and
can actually be enjoyable if properly mentored and taken in stride.
The payback for weather knowledge is making aviation work better for us
through safer, more comfortable, and enjoyable flying, which is also far less
intimidating to accompanying friends and family. We remember that this flying
business is not a 100 percent completion operation … we’ll spend some nights in
unique motels. Those nights will quickly pass in trade for the many flights we do
complete that offer us utility and pleasure from being flown knowledgeably and
without angst.
Obviously, few of us will be meteorologists enough to know all the situations.
A good meteorologist pursues extensive and on-going study of the science, then
develops the innate skill of an intuitive investigator. However, we can protect
ourselves in two ways: one, never be smug about a forecast, and two, while
flying, keep up with the weather by periodically getting current airport weather
and then comparing it with what the forecast promised. If there is a difference,
such as lower ceilings and/or visibilities, or the weather is not improving as
forecast—anything not as originally forecast—then it’s time to check more recent
METARS, get new forecasts, and find out about any new or updated SIGMETs,
AIRMETs, PIREPs, and Convective SIGMETs; as well as investigate through
satellite and NEXRAD, if we have that equipment onboard our aircraft. When
things begin to look poorly and are not working out as expected, it is also a time
to review and recompute our fuel supply, at the same time thinking which way
we’ll run to stay out of trouble.
With weather information a mass of codes and formats, it’s important to
remember that they periodically change. Though sometimes subtle, there are also
times when big changes occur, as in 1996, when METAR and TAF were
introduced and our Fahrenheit world became Celsius. At the time, few liked the
change, but it happened, it’s now everyday stuff and life goes on. This is a
reminder that with aviation information often critical, we have to go with it and
keep on top of things.
The constant changes to weather information not only helps pilots directly, it
enhances forecasting. One example was the introduction of Automated Surface
Observation System (ASOS ) and Automated Weather Observing System (AWOS ).
The great part is there are now hundreds of airports reporting weather; a majority
of smaller airports considerable distance from larger airports that are reporting
METARs and Automatic Terminal Information Service (ATIS ). Checking these
many ASOS/AWOS airports by electronic access, listening on radio while flying
by, or calling ahead on their individual telephone numbers, (available in the
Aeronautical Information Manual (AIM ), the Airport/Facility Directory (A/FD ),
as well as off the FAA’s website www.faa.gov ) , can reveal weather issues even
before we depart. This data is filtered through the aviation weather system,
allowing us to have it in aircraft via data link to Electronic Flight Instrument
Systems (EFIS). It is also used by the NWS and affiliates to improve forecasting
accuracy, which along with other information leads to the previously mentioned
data for icing, thunderstorms, turbulence, and so forth. With all of the data put
together in flight-planning presentations, not to mention the model concept of
weather forecasting and easily available atmospheric information … well, it goes
on and is a book in itself. We think it makes investigating weather fascinating, as
well as enhances our use of aviation.
However, even with all this, it will still be the pilot’s responsibility to get the
weather, interpret it, decide what to do about it, and be suspicious of its fickleness.
Of course, a pilot must always be aware that technology can hiccup and miss the
weather, tell it wrong, or forget to put it out at all.
There are various ways to keep up with weather as we fly, and more on that
later, but there are a few methods worth mentioning now—even if we repeat them
later on:
1. Through our aircraft radios, we should ask and listen for weather updates on
Flight Watch (EFAS)—122.0 MHz. If Flight Watch is unavailable, we can get
the information by contacting the FSS. Also, please give PIREPS—they are
the only source of real conditions shared for other pilots and can be extremely
important as go–no go information or as an alert for imminent weather safety
issues. It is especially helpful if we are the first flight of the day.
2. As you fly, listen to ASOS, AWOS, and ATIS for the current weather at
airports along your route, noting if they are different from forecast. If so, it’s
wake-up time to learn what’s happening. ASOS/AWOS are usually minuteby-minute weather data, whereas ATIS is from observations up to an hour old.
There are, currently, nine different versions of the popular AWOS, but most
have the key weather data of altimeter setting (pressure), wind, temperature,
dewpoint, and density altitude. Better systems emulate ASOS, adding
visibility, cloud ceiling, and precipitation identification. High-end AWOS gets
into lightning and thunderstorm data. However, because these systems take
observations as though looking vertically through a narrow funnel, they can’t
tell us what the surrounding weather is (fog bank north, clouds on hills, etc.),
nor do they warn of approaching thunderstorms, except when they are directly
overhead, and then only in those versions doing so. Some AWOS systems,
however, have the ability to inject human observation, which brings us back
to the quality of original human-observed weather reports. ASOS and AWOS
weather observations are considered good for a 7-mile radius, so in between
we rely on area forecasts, PIREPs, radar, and so on. Sometimes the systems
can seem inconsistent, with visibility possibly confused by haze, ice crystals,
and snow. Fluctuating temperatures can be caused by clouds drifting over.
Winds, clouds, visibility, and precipitation seem out of whack due to a passing
shower or thunderstorm or even a good thermal or dust devil. However, these
anomalies are small compared to the excellent benefit of ASOS and AWOS,
and they are improving all the time.
3. Hazardous In-Flight Weather Advisory Service (HIWAS ), available on
selected VOR frequencies, gives us a heads-up to contact FSSs or Flight
Watch for details.
4. The most important way of gathering the latest information is to look through
the windshield at the signs of weather: clouds, sky, precipitation, ice,
thunderstorms, wind on the surface, and anything else in the atmosphere.
There will be constant improvements allowing better information, userfriendly displays and communication sources. But forecasting will never be 100
percent accurate, so the final weather responsibility will always be ours! In short,
as my son said: “the sky is weather and the sky is where we fly … learn it.”
You Are the Captain!
As we’ve tried to make very clear, it is the pilot’s responsibility to get the weather,
analyze it, and then take action. It’s more difficult for lower-time pilots to make a
decision after looking at the weather briefing material, but regardless, the final
decision to go or not must be theirs. FSS specialists have made mention that pilots
frequently ask “Should I go or not?” This raises the hackles on experienced pilots
who have spent a lifetime protecting the command authority of pilots; take that
away and you might as well give up f1ying. It’s the sacred part, because the pilot
finally is responsible—attend an accident hearing and see how true this is as the
blame is placed on the pilot, as it is about 80 percent of the time. Aside from that,
no one knows how a pilot feels, not just the physical feeling for that day, but how
the pilot feels about his or her experience level, ability, aircraft, and equipment.
If pilots don’t maintain a sense of control over their operations there will be a
degeneration of command, and it’s not impossible to visualize a ground-based
government “dispatcher” telling us if, how, and when to fly. Worse may be
considerable restrictions to our flying, training, and so on. The powers that be
measure concerns from incidents, (accidents) and public concern—often the
nonflying public. At this writing, this issue needs serious improvement.
It is appalling to think of a pilot asking a briefer whether or not to fly. If a
pilot cannot make that decision and has to ask someone else to make it, then the
decision has already been made, because if there is that much doubt and
uncertainty, then the pilot should stay on the ground. The uncertainty is the
decision!
*
terms briefer and specialist both used for the same FSS person who provides
briefings and information to pilots.
1 . NOTAM: Notice to Airmen. These reports include things like a VHF omnidirectional range (VOR) being out, runway out of service, etc. Obtained during
briefing and when requested.
SIGMET: Significant Meteorological Information. Issued when significant
weather may affect the safety of all aircraft. These reports include severe and
extreme turbulence, severe icing, and visibility less than 3 miles in sandstorms,
dust, or volcanic ash.
Convective SIGMET: Convective Significant Meteorological Information.
Issued for thunderstorms (TRW) and imply severe or greater turbulence, severe
icing, and low-level wind shear. Some of the criteria include a line of
thunderstorms at least 60 miles in length, with TRWs over at least 40 percent
of its length. Also, an area of 3,000 sq. miles or more with 40 percent storm
coverage, as well as tornadoes, line squalls, embedded thunderstorms with
wind gusts of 50 knots or more and hail of ¾ inch or more. This stuff is bad in
any form, so just because it might not be up to the SIGMET criteria, does not
mean it’s smart to fly in it.
AIRMET: Airmen’s Meteorological Information. These are notable weather
phenomena of less intensity than SIGMETs. Also including areas of at least
3,000 sq. miles having cover moderate icing, turbulence, winds over 30 knots,
ceilings under 1,000 feet, visibility less than 3 miles, mountain obscuration,
and other nasty things. AIRMETs apply more to small aircraft without
abundant equipment and performance, but are still worth listening to for the
big boys. An AIRMET may be part of an FSS briefing. These all are issued as
needed, and you pick them up by warnings on certain VOR stations, Flight
Watch, ATC, FSS, as well as NWS computerized products.
PIREPs: Pilot Weather Reports. It is just what it says. Call the FSS on radio or
telephone, either directly or through the EFAS—radio call “Flight Watch”—
and give your flight conditions. PIREPs are solely dependent on pilots’
reporting; the information is often extremely helpful and sometimes critically
so.
4
Checking Weather and the Big Picture
The flight begins when we start to think about the weather, look over the data, and
scrutinize all the information available from the multitude of sources we have
already talked about. But in this world of electronic weather information, there are
many more places to look.
A standard weather briefing aside, what is a basic, commonsense look at what
we check and how—before, during, and after flight?
1. The big picture—the synoptic. Start this a day or so before, using
computerized weather maps, which make this easy but detailed, and calling
the FSS for an Outlook Briefing. Barring this access, we can watch television
weather.
2. The forecasts—airports en route, departure and destination, area forecasts,
upper air winds and temperatures, and outlooks for ice, turbulence and
thunderstorms.
3. The latest hourly reports (METARS) and then past reports—what has it been
doing and what is it doing compared with the forecast?
4. In-flight—keep alert to the situation by obtaining current reports—what’s
actually happening, forecast revisions, SIGMETS, AIRMETS, PIREPs, and
what you see out the window. Listen to other aircraft on EFAS and Air Traffic
Control (ATC), being alert to any problems they are experiencing and the
weather information they are requesting. Listen to ASOS/AWOS/ATIS for
airports you are flying over or near, checking to see if their reports conform to
the forecasts. If data-link weather information is available, keep tabs on radar,
satellite, and so on.
5. Manage the flight with the information, and be ready to take alternate action.
6. For learning purposes, and to build experience, take a moment after landing to
inspect what happened in relation to what you thought would happen before
takeoff. If possible, talking about the flight with the FSS or NWS is
worthwhile and justified; they may appreciate it, because you can tell them
what’s actually up there.
The Big Picture
As noted, our number one weather briefing interest should be the big picture—the
synoptic—which tells us the orientation of fronts, highs, lows, and other general
weather. Often during a briefing, the synoptic is passed over as we eagerly look
toward the “actual” weather. This isn’t smart, as the synoptic should be thought of
with care, as it is the foundation on which we build our weather picture. It should
pose questions such as: Where does my flight route pass in relation to the fronts,
highs, and lows? How would changes in the picture (speeding up, slowing down,
or stalling of weather movement) affect my flight? What kind of weather do these
fronts and systems have? Ice, thunderstorms, low ceilings—what do they mean in
relation to our equipment and ability? And what about the synoptic’s past? Has it
been behaving as predicted, or has it been inconsistent?
In studying the synoptic, it is important first to see an actual picture. If we do
not have maps and charts, 1 it is difficult to try and create a picture by either
grasping text descriptions of the weather layout as we read it from a computer, or
writing it down and picturing what is being told to us by an FSS briefer. Adding to
this difficulty is the special language computers use in describing weather and its
location; a language developed for convenience to the computerized system, not
ours. Yes, today’s computerized weather information often has the ability to
decode its unique language into normal text, but total dependence on this is not
prudent. This cryptic jargon is something we must learn well, whether for
understanding text weather should it not be decoded—yet may be critical—or also
for using it as a kind of shorthand when writing it down, as when heard over the
telephone or radio. It’s particularly confusing when the cryptic message “defines”
the location of, say, a line of thunderstorms or fronts, by reference to a series of
obscure station identifiers that are, at best, only vaguely familiar.
For example, try making a synoptic picture in your mind of the following
actual message from the Dallas Area Forecast; first will be a synopsis of the
general weather setup—highs, lows, and fronts—then a regional forecast for
Central and Eastern Oklahoma. (They are copied verbatim from the actual
forecast, but we’ll add a translation under each one.)
DFWC FA 101945
SYNOPSIS AND VFR CLDS/WX
SYNOPSIS VALID UNTIL 111400
CLDS/WX VALID UNTIL 110800…OTLKVALID 110800 – 111400
SYNOPSIS…TROF OVR WRN TX BY 14Z OVR S CNTRL TX. BY 00Z
CDFNT WL MOV OVR OK/TX PNHDL-SERN NM-FAR WEST TX BY
14Z OVR SERN KS-W CNTRL OK-W CNTRL TX.
[The Dallas area forecast was issued on November 10, 2012, at 1945Z, and
is valid until November 11th at 1400Z. (Month and year not in actual data, but
added here for originality sake.) The clouds and weather forecasts run until
0800Z on the 11th, but the outlook is valid from the 11th at 0800Z until the
forecast ends on the 11th at 1400Z.
Synopsis … at the time the area forecast began, a trough is over western
Texas, and by 1400Z it will be over south-central Texas. By 0000Z on
November 11th, the cold front will move over Oklahoma and the Texas
Panhandle through southern New Mexico and Far West Texas. By 1400Z, the
cold front will be over southern Kansas through western-central Oklahoma
through western-central Texas.]
OK CNTRL…SCT045 SCT150 SCT-BKN CI. 03Z BKN050 TOP FL180.
ISOL-TSRA. CBTOP FL400. OTLK…VFRTSRA 09Z MVFR CIGTSRA.
ERN…SCT040 SCT150 SCT CI. TIL 00Z WND S 20G30KT. 04Z BKN040
TOP 080. OTLK…MVFR CIG 10Z TSRA.
[Over central Oklahoma … clouds scattered at 4,500 feet, scattered at
15,000 feet, and broken cirrus (that’s way up high). At 0300Z clouds broken at
5,000 feet with tops to flight level 180 (18,000 feet). Isolated light
thunderstorms and rain (a light thunderstorm is still a thunderstorm and should
be avoided—ROB). Thunderstorm tops to 40,000 feet. Outlook is for VFR
with moderate thunderstorms and rain. By 0900Z marginal VFR conditions
due to ceilings and moderate thunderstorms.
Over Eastern Oklahoma … clouds scattered at 4,000 feet, scattered at
15,000 feet, and scattered cirrus. Until 0000Z, wind is to be south at 20 knots.
Gusting to 30 knots. AT 0400Z, clouds become broken at 4,000 feet with tops
to 8,000 feet. Outlook … marginal VFR due to ceilings and after 1000Z,
moderate thunderstorms and rain.]
While a rough mental picture can be created, the details are missing, and that’s
a lot of information to stuff into our heads. As the old saying goes, there’s nothing
like a picture, and in this case an actual surface weather map. If a map has been
seen before the above synoptic information is read or delivered to us over the
phone from the FSS, the text or telephone description makes better sense.
In the text-weather example above, we note that although thunderstorms are
not forecast in eastern Oklahoma until 1000Z, they are forecast to begin in central
Oklahoma at 0300Z. This is a clue that tells us to check for developing
thunderstorms, comparing time of development to the forecast. In the above
example, an excellent enhancement would have been Next Generation Radar
(NEXRAD) or even a relatively current satellite image. Now we would have a
picture of actual weather, making our thunderstorm check easier. But let’s say we
don’t have NEXRAD.
We’ll say our flight is heading into Oklahoma City (in central-eastern
Oklahoma) from the northeast, kind of partially paralleling the approaching cold
front. We’re planning to arrive about 0400Z. We are kind of tight on time for
missing the thunderstorms, but this evening that’s the way our schedule worked.
Suppose we are flying on instruments without radar or at least a lightning
detection system, 2 feeling smug because we expect to get there ahead of the
thunderstorms. Then some information from Flight Watch, ATC, or a new
Convective SIGMET tells us of an earlier development or weather movement,
alerting us to thunderstorms popping up ahead of schedule. It’s a double concern
with respect to running into storms; one is the concern of beating them into
Oklahoma City, and the other is meeting some activity ahead of the front, which
may force us east and away from our course, as well as our destination. Suddenly
we aren’t so smug anymore, and it is time to think about avoiding untimely
thunderstorms as well as checking our destination weather, consider time en route,
fuel, and possible diversion. Also, being on instruments around embedded
thunderstorms, without radar or a lightning detection system, isn’t a happy
situation! So now that we’ve tested our mental geography, let’s look at a sample
surface chart, on page 34, for our above example.
Synoptic Surface Chart valid at 0000Z on the November 11, 2012 … the
corresponding map for the forecast above. Now we can run through the synopsis
again and see that it corresponds pretty well, especially the 0000Z forecast for the
cold front position. The trough (the dotted line into Mexico) seems to be a bit
behind and must rotate into Texas to follow the forecast. The weather north of the
Dallas Area Forecast is covered by the Chicago Area Forecast, which we’d call
up if we were going that far.
With the real picture in mind we see the orientation of the frontal systems,
which makes it easier to relate those thunderstorms to an actual geographic
location. We would know that the development of thunderstorms “after 03Z” will
be dependent on the movement of the fronts, and for that matter, the whole system
of fronts, highs, and lows. By obtaining current reports as we fly and keeping tabs
on how the weather is actually moving—faster or slower—we can apply that
knowledge to the 03Z forecast and determine how we stand. If we do not have
access to a printed surface map, we can draw weather maps, crude and simple
though they may be, sketching the confused messages of fronts and storms on our
navigation charts or a small blank copy on a flight plan form. We have used
plasticized Weather Advisory charts, either purchased from pilot supply stores or
copied from the NWS website’s “AWC Advisory Plotting Chart.” Those “not for
navigation” plasticized maps used for airline passenger announcements have
enough aeronautical data to make them useful for grease pencil sketches of
convective SIGMETs, turbulence areas, and synoptic setups.
In today’s world of easily accessible weather information, it seems oldfashioned and improbable that we would not have some sort of synoptic weather
image, or for that matter, any map or chart product. With graphic presentation of
maps and charts, thunderstorms through NEXRAD, and all sorts of other
information, we can easily form a big picture concept. However, there are times
we may not have this big-picture weather information, which makes it harder to
have solid planning for options before we begin our flight. We have to become
very clever with voice weather information en route and having good old-school
“in our head” imagination of geography and the synoptic weather concept, which
used to be the only way and, for some, still is the case. That’s okay, as long as
we’re sharp in doing so. The problem here is not having the total mental picture
correct, then flying up to a “wall” of weather problems, while at the same time
being trapped—unable to turn back or escape and in the middle of something we
can’t handle.
No Surprises
With this big picture in mind, plus carefully monitoring its movement—especially
in today’s world of so much available weather information—we should never
have surprises, get caught in nasty situations, or have to use that timeworn alibi:
“The forecast wasn’t any good.”
Satellites and Some NEXRAD
Satellite and NEXRAD weather images can be of huge help. We ought to talk
about them as an accessory to the total answer of big picture weather. They are an
excellent addition to the many sources of computerized weather information.
First, satellite images are not the actual raw photo but are enhanced by various
processes. This isn’t something bad. It actually improves the picture, but different
methods make the pictures a little different. Infrared is used to give temperatures
of the clouds. That’s how meteorologists tell tops, but sometimes, with snow
cover in winter, the information is difficult to interpret. If the image shows no
clouds, we’re looking at ground or sea temperatures. Water vapor satellite images
display water vapor quantity in the middle to upper troposphere, (700–200
millibars [mb], or about 11,000 feet on up to about 39,000 feet). This is not
precipitation, but moisture hanging around in our atmosphere’s make-up; water
vapor satellite image’s best use is showing movement of weather systems, jet
streams, and thunderstorms. Both IR and water vapor can be seen as a night
image, but regular visual satellite, like our eyes, sees nothing at night.
Satellite images, like weather maps, have to be related to time, and the most
value comes from the latest picture. When we look at commercial TV coverage
and satellite images, the time the images were made, which should be shown, is
generally unknown. However, with aviation weather services, the image time is
given which not only allows important comparison with forecasts, but also
function as a check on the time maps and images that were produced versus when
they were made available for our viewing. For example, look again at the map on
page 34; although a surface map (analysis), this concept is important whether a
map or satellite image. It was valid at 0000Z, but was not issued until 0122Z, so
the data on the map is an hour and twenty-two minutes old, when we first see it.
That delay under a big sleepy high pressure is one thing, but the position of a fast
moving front or squall line could be critical. So on surface maps where we are
evaluating data for the present, it really isn’t. This time issue is important, will
come up again in the book, and is the reason we need to check actual current
weather to jump this time gap. With satellites this delay is less, but never the less
worth noting. And NEXRAD delay? That’s a big deal, which is discussed in
Chapter 15 on thunderstorms.
When we add NEXRAD to a satellite image and/or surface map, we’re really
getting a complete picture. Since NEXRAD is a “look from above” of
precipitation, just as is a satellite image, we get an overall big picture view.
However, after that moment of observation, it has changed. More on that will be
mentioned next.
What Do Satellites Show?
We see that satellite images show cloud cover and, to some degree, how thick the
clouds are, but the pictures do not tell cloud bases or ceilings, and they don’t tell
the height of cloud tops, although satellite experts say they can tell top heights
within 2,000 feet. Infrared image plays the big part in this situation. The images
also show convective activity—thunderstorms—as bright white blobs and lines in
daylight or by infra-red at night. However, when this occurs, NEXRAD or Radar
Summary charts give a better idea of thunderstorm areas. NEXRAD is timelier
than the Radar Summary chart; the latter has worked for years and still can if we
don’t have other sources. Both NEXRAD and radar summary charts can give us
data on storm heights and directions, defined areas and lines, and so on. The big
advantage to NEXRAD is that it’s so easily displayed, from many potential
sources, both before our flight begins and in-flight via data link to aircraft with
electronic display capability. It should be remembered that this combination of
images, charts, and digital electronics is a good reference for planning how to
avoid an area of thunderstorms, but in no way should it be used to weave through
a mass of thunderstorms; this takes airborne radar, maybe further enhanced with
NEXRAD and lightning detection equipment as supplements.
An infrared satellite image at 0200Z on November 11, 2012, two hours after the
surface chart on page 34, and valid for the time-frame of the earlier area forecast
example.
A NEXRAD image for 0215Z on November 11, 2012, again about two hours after
the surface chart on page 34 and respective area forecast.
The infrared satellite and NEXRAD images, along with the surface chart of
page 34 and the area forecast of page 33, gives us a full picture of what’s going
on. In our flight example, we see the cold front is about where it should be per the
area forecast and extrapolation of the surface chart, but it is drier into north
Texas and on south. That low pressure on the border of west Texas and Mexico
rekindles some weather.
There are thunderstorms in west-central Oklahoma, verified with tops about
37,000 feet; but that’s then, and could be changing rapidly, because those wind
arrows say some storms are moving faster than 30 knots, which is a cause for
concern. We’ll talk more about storm velocity versus severity in Chapter 15 on
thunderstorms. The satellite image shows some lighter shade cloud near
Oklahoma City and a dim echo on the radar; maybe it’s something forming ahead
of the front, so we need to keep our eyes open. The bright white of the satellite
image into central Kansas and eastern Nebraska indicates a line of
thunderstorms.
Potential thunderstorms extend all the way north along the front, to that low
pressure in western Minnesota. We can see the less dense cloud turning west,
probably lesser activity associated with the trough shown on the surface chart,
extending northwest from the Minnesota low pressure. There is a lot of moisture
slinging counterclockwise northwest of the low, and the brighter the white, the
thicker. If cold enough, there is ice potential, and NEXRAD also shows some tops,
so there’s convection in one form or another. There is also quite a bit of less dense
cloud color—lower tops—maybe a few hundred miles west of the front, over the
western Dakotas and Nebraska. That’s typical backflow around a low and
probably a stratocumulus deck, with tops possibly approaching the teens and
again, if cold enough, icy. This comes up again in Chapter 16 on ice.
We see other activity north of the stationary front to the east across the Great
Lakes, and again some higher tops are shown on the radar. That’s another story,
and it’s a big country. Overall, with this satellite and NEXRAD data being for the
evening, we see most thunderstorm activity as being caused by frontal effects. If it
were daytime and warmer, along with frontal effects, it might get real spicy—
something to think about if we’re heading back east the next day.
The gray scale across the top of the satellite image shows temperature and
therefore cloud tops. Dull gray is probably lowish stratus, as mentioned earlier,
while bright white indicates very high tops—again, that thunderstorm indicator.
What are the best uses for satellite imagery? First, they confirm what the
weather map is saying. The clouds of the satellite image should corroborate the
weather map’s structure, and it should be easy to pick out front locations as well
as post-and prefrontal cloud masses. If the picture and the map do not match, then
it’s time to dig deeper and learn what’s wrong. The first thing to check is how
close the times are between the satellite image and the weather map. If the weather
map and satellite picture have been produced many hours apart, this could account
for the differences. If this isn’t the problem, then we should be suspicious that the
weather isn’t working as the map and forecast indicated it would. We talk about
this concept later, but basically it’s a job of checking actual reports against
forecasts.
Frequent satellite images give us an opportunity to study a series of them,
seeing how the weather has moved over a period of time. With this capability,
pilots can see if the weather is moving off course or becoming thicker and
clobbering the route we plan to fly. With today’s computerized weather, this issue
is enhanced by “looping” of the satellite image. For that matter, modern
computerized weather loops everything: satellite, NEXRAD, and just about every
map, chart, or graphic out there. That’s also what they show on TV. However,
when we loop weather using a computer or personal electronic device, we can
slow images down or use stop-action to better analyze whatever we’re
investigating.
We again look at the fact that satellite looping is what has already happened to
the weather and not what will definitively happen in the future. What we see in
this past image is the direction of weather movement, trends, and timing—fog
dissipation, growth or dying of convective weather, but most importantly the
overall flow (winds aloft) of weather systems, high and low clouds, and so forth.
It is this visual rhythm of the sky, from which we can sketch a fairly decent
forecast, whether on paper or in our heads. This can give us fair judgment of what
will influence a flight. Actually, it seems sometimes it is easier to memorize an
image in motion rather than a stationary one. A great education is watching the
looping of different weather setups, at different times of day, then comparing them
with forecasts and “the big picture.”
There are certain sources of “forecast” radar, which could really snare the
unwary. It is just that—a forecast—and not to be depended upon as actual future
convective weather. It might have fair possibility of accuracy to an overall area of
future convection, but the reality is that convection/thunderstorms are where they
are when they happen. To guess or assume otherwise is dangerous game.
For the VFR pilot, satellite imagery is especially useful, because the pilot can
then see where there are clouds and where it is clear. If the flight is over a long
distance, the satellite picture can help the VFR pilot plot a course around all
clouds, again enhanced by looping, and tells where the weather may be headed or
changing. Just remember, we need to be open to change, since it is a guess from
the weather’s past movement. If the VFR pilot finds it necessary to go through an
area where the picture shows clouds, then it’s a job of checking actual reports
such as METARS, ASOS, AWOS and so forth to see what those clouds are doing
to ceilings and visibilities, then—very importantly—what they are forecast to do.
There is a lot satellite imagery can do for us, whether we are flying IFR or VFR.
Besides the previously mentioned convective weather, general cloud structure and
air mass flow, we may see areas of fog, lenticular clouds lined up to show
mountain wave conditions which give us hint to strong winds producing
turbulence, and in cold weather, potential ice-producing clouds, just to name a
few.
Back in 1974, your two authors used satellite images while flying a Cessna
402 across the Pacific Ocean to Australia. The mid-Pacific stops were exotic atolls
and islands, but lousy on weather information. For some reason of South Sea
mystery, once beyond Honolulu, we could only get faxed satellite images and
some printed weather. At Tarawa and Guadalcanal (yes, for real), the airport
facilities were small offices with a lonely fellow who was obsessed with correct
completion of the then tortuous International Civil Aviation Organization (ICAO)
flight plan; my father was mysteriously absent every time we had to fill it out.
This all in between the fellow turning around to a high-frequency radio and
working static-infested communications with someone hundreds of miles away,
giving an aura of exotic oceanic aviation decades earlier; and exactly my father’s
point of the trip! Anyway, the satellite images let us look at the synoptic picture
and some wind verification over a time sequence. Fortunately, the mundane
weather of the central and south Pacific, during that time, helped make the satellite
guesses pretty much dead on.
When using satellite images, pilots learn more about them and the techniques
for deciphering them. Asking questions of a meteorologist, if we are lucky enough
to see a real one, will improve our knowledge of satellite images’ usefulness.
Despite the earlier sea story, it is important to remember that these images are
normally not the only weather information available and should not be used alone
to make decisions. We still need forecasts, actual current reports, and all the rest,
including weather maps and charts.
Valid Old Map Thoughts
As mentioned previously, before computerization, hence printable or constantly
accessible maps and charts, if you wanted one to carry along on your flight, you
had to be creative; this is where one would draw a weather map on a napkin, flight
plan, or your navigation chart. Also, if you could not get a forecast map, but had
previous maps showing a weather system’s speed of progress, you could estimate
its future path. Tracking time of weather movement, which gave a wag on what
was ahead.
In 1965, I (RNB) stood in a weather office in Buenos Aires looking things
over for a flight to Christchurch, New Zealand, over the South Pole. Since that
wasn’t a regular route, the weather information was slim. The only weather map
covering the other side of the globe was a day and a half old. We made an
educated guess. Nieut Lieurance, the weatherman with us, guided our guessing,
and he thought a front would go through Christchurch six hours before our arrival.
He hit it almost on the nose, and after a 14-hour flight, we arrived over
Christchurch in sparkling, clear air washed clean by a recent frontal passage. Not
the way we like to do business, but much better than nothing. The big picture had
told the story.
While again it would seem rare these days to not have some sort of portable
weather map, it does happen. I (ROB) have always been an avid user of daily and
accurate newspaper surface maps. The New York Times was a favorite, with a
mid-week and weekend series of forecast maps, including a jet stream outlook.
(The Penn State Meteorology Department still provides the Times ’ fine maps.)
Torn out, the little pieces of newspaper lived ready for action in my uniform
pocket. Antiquated, yes, but the point is, if we want a map and can’t get to a
computer or TV, we can look for good newspaper maps with fronts, highs, and
lows, not cute little clouds with sun or lightning bolts. The point we are driving
home is not to let our aviation endeavors get too hung up on technological peer
pressure or seduction, throwing out proven methods just because it’s oldfashioned, especially when the new era doesn’t produce something we need and
the old can provide it. Common sense and simplicity can still go a long way.
Anyway, the best part of carrying a newspaper weather map on the airline was
pulling it out and giving it a serious study when the FAA or a check pilot was in
the jumpseat.
Where We Find This Computerized Weather
Today, however, it is more than likely we have some form of graphical weather
display, from traditional surface and upper air charts, to in-flight warnings, area
weather, forecasts, convective weather, icing, turbulence, and a lot more. Also,
much of this data can have that looping mode to give rhythm to the sky;
remembering looped data is what has happened versus what is supposed to
happen whether it’s a guess off looped data, or published forecasts. We also
remember that the shorter the forecast, the more potentially accurate it is, but not
an exact look towards the future. The weather is only exact when we are in it.
So where do we get all these weather graphics? There are a lot of computerbased products, from many different sources, whether retrieved off computers,
dedicated electronics or personal electronic devices. The most consistent sources,
as mentioned earlier, are the National Weather Service and their web-sites of the
Aeronautical Weather Center (AWC) and Aviation Digital Data Service (ADDS ).
They offer a complete menu of maps (charts) and required aviation weather data.
Then, through the menu of these sites, we can dig into an almost endless path of
information and tutorials. We also like referencing the Weather Prediction Center
(WPC ), formerly called the Hydrometeorological Prediction Center (HPC ), with
its website offering more detailed maps and forecasts; HPC supplies a lot of the
data that feeds the NWS. The Storm Prediction Center (SPC ) focuses on mostly
convective-related weather (thunderstorms), adding detail to what they provide to
the AWC/ADDS sources. (Refer to the Suggested Reading section for access to
the above websites.)
When we access flight briefing websites such as DUATS/DUAT and the many
other application-based products on personal electronic devices, they include
various maps necessary for our briefings. If, however, we want further detail, we
again encourage use of the above references. However, like so much of today’s
computerized information, there is extensive data available and numerous sources
for it, far beyond the space and scope of this book. This will come along as one
delves into the study of weather, but we do recommend the earlier mentioned joint
FAA and NOAA publication of Aviation Weather Services Advisory Circular AC
00-45G as the official explanation for the core of the government’s weather maps
and data. It’s available on the Web at www.faa.gov , but a printed copy for quick
and easy reference is always helpful; these are available from aviation supply
sources.
A few thoughts on television weather. It certainly is not any sort of approved
weather—primary product or otherwise—but it is something many pilots watch,
so it seems worth mentioning. With today’s weather-dedicataed TV channels such
as the Weather Channel , and many local stations presenting fairly detailed
weather, a look at their surface maps, radar information, or satellite images can be
a worthwhile, big picture glance. The only problem, as said before, is verifying
the time and accuracy of these presentations; this isn’t always easy to do. A good
place for TV weather is when you are running around the house or hotel room,
getting ready to leave for a flight. It’s best used as a heads-up situation, after
which we research official weather through aviation sources.
One day, before the computerized weather era, I (ROB) took off from Atlanta
into a summer afternoon filled with happy, low-topped, fair weather cumulus. The
weather information had not mentioned any significant Convective SIGMETs;
that system was still relatively new. However, when I was packing for the trip, the
then-new Weather Channel had highlighted a potential line of thunderstorms
percolating to the west of Atlanta. Remembering that black-and-white TV’s
afternoon forecast map, we turned on the radar. Just as the radar lit up, a bright red
line of weather lay not far ahead of us, and at the same time we popped through
the tops of those fair weather cumulus, staring face to face with a wall of water
towering into outer space. There was not much time to avoid it, so we told—not
asked—ATC which way we were turning and did, avoiding a wild ride. Today
we’d most probably be well warned from Convective SIGMETs, a good look at
NEXRAD radar through some electronic device, calling the FSS, and yes, maybe
the Weather Channel . Without some sort of electronic weather information or a
phone call to the FSS, that TV weather might be very useful.
A last thought on TV weather. When stations like the Weather Channel run
episodes explaining weather phenomena, and all that makes them happen, we can
learn quite a bit. They also run synopsis forecasts and long-range outlooks that
can be quite helpful to that big picture of the weather; again, not official aviation
weather but a good synoptic look. This is a great stride in making the public more
street smart concerning weather. Television weather is worth watching, not only
for what it has to offer, but hopefully to inspire us to learn more through personal
study. For example, the constant discussion, explanation, and TV presentations of
“weather modeling” are bringing us up to speed on what’s going on in the
backrooms of our forecasting weather world. We can find these models ourselves
on the Web at the AWC/ADDS/ HPC and other places.
Get the Picture First
As we now realize, there’s lots of data out there to provide a good picture of the
general weather. The key point is to get this picture and visualize it before setting
up your weather briefing. Then it will be much easier relating to the data we
retrieve from a FSS specialist’s words or what is divulged as we pick data off a
computer or personal electronic device. This makes it easier for everything to
soak into our heads. Now we have a total picture of what’s out there.
Another point worth repeating is that if we use weather information that is not
an approved product, such as TV weather, it should not take the place of a proper
briefing! An important point.
On Days Off, Too
With weather information so readily available, electronically or otherwise, we can
look at it daily. We have the opportunity to keep up with weather and be
conscious of its movement and development, even on the days when we are not
flying. This allows us to better judge weather and hopefully, become more
intrigued and curious.
A daily look at good weather maps, a decent TV weather station, or if really
curious, some of those weather models, we can keep pace with the flow and
development of how the sky is behaving, whether it is erratic or reliable. There is
a cadence to the sky, so on the days we do fly, if we have been keeping up with
things, it will be easier to pick up the action, understand the situation, and be
ready for the demands it may place on us. The weather situation will be easier to
cope with if we’ve kept abreast of it. This is all part of weather and flying being
one skill. Suddenly, the sky opens up to an interesting world previously taken for
granted and little understood. Aside from all that, it’s fun.
A Deeper Look at The Map
What does a weather map show? First, we remember that the information is old
when we look at it, and by the time we use the information, it will be older still.
This is all a reminder that weather is always in motion, it moves and changes, and
the movement and change are the things that make it necessary for a pilot to keep
an eye on the action all the time.
How many hours ahead we want the forecast to be is a key factor in
determining how accurate it is or will turn out to be. Will the ceiling be above
limits for the next hour? A forecast of that can be pretty accurate. Will it be above
limits five hours from now? That’s more difficult to call, and the accuracy has
moved from near 100 percent to something quite less. Will the ceiling be above
limits five days hence? Now the accuracy is way down. So it is important to relate
any weather information to the time it was forecast, the time of maps and satellite
images, the time of winds aloft, and the time an actual report was made. Time
difference directly relates to how confident we are, and the caution needed, in the
use of any weather information. As mentioned earlier, a pilot should, as a habit,
look first at the day and time noted on any weather information before considering
it. We have another example relating to the Prognosis or “Prog” Charts, which are
available off the NWS’s ADDS website. They give different forecasts—or
prognosis, hence their name—of the surface weather over 6-or 12-hour time
periods. We occasionally may see the same map validity time on two different
forecast periods. Looking carefully at the bottom of the chart, we see that the
“issued” time is different between the two, so one was created later than the other.
That later one, obviously, is the important and more valid chart. However, we still
look at the old one, comparing the changes, which tell us how the forecast has
changed.
A weather map is like a snapshot. If the shutter clicked at 00:00 hours Z time,
Universal Time Coordinated (UTC); that was the moment everything stopped, but
at 00:01, it started up again, the characters moved in their own way once more,
and the map you saw at 00:00 hours is no longer valid.
What isobars mean on a weather map.
A weather map reminds us of a work of art; the sweep of isobars and fronts is
graceful and pleasing to the eye, as is so much of nature’s work. But there is more
than beauty; there’s also an important story. At first it may seem surface weather
maps are confusing with all the numbers and meteorological hieroglyphics
clustered around the various airport locations; these are known as station models.
Actually, that information is mostly for meteorologists. What may be interesting
for us in those numbers is found in the actual weather reports; METARS. There
are important things we do want from a surface map. Most important is where the
fronts, highs, and lows are located, and how the isobars curve, because they
picture the wind flow and tell us from which direction it is coming. Isobars also
tell us the velocity and source region, telling us from where the air is coming and
what it’s like—cold, hot, wet, dry, stable, or unstable—which in turn tells us about
the weather.
When we see a deep low in the vicinity of British Columbia, with isobars on
the westerly and northerly sides that sweep generally in a southeast direction and
are packed closely together, we know immediately that cold, wet air is being
swept into the area, and that it’s pushed by high-speed winds, because the closepacked isobars tell us the wind is howling. There will be lots of wet weather in the
area: low clouds and rain, with big snow in the mountains, and wind, lots of wind.
During winter in New England, a low off the Maine coast will act the same,
sweeping inland with easterly winds and blizzard-like conditions.
Another day, another map. A northwest flow is over the Midwest, with the
isobars coming from continental Canada, and we know the weather will be
excellent, with fair weather cumulus and good visibility.
A flow from the south and southeast in the center of the United States means
hot, humid air is flowing from the Gulf of Mexico, creating thunderstorms. If a
cold low of north winds is headed toward the Gulf, then the two air masses will
meet as a cold front and that will make for very nasty thunderstorms and even
tornadoes. This setup is unique to the United States—the cold winds that can flow
southward from arctic regions without obstructions such as a mountain range, and
the warm, wet winds from the Gulf of Mexico, likewise flowing unobstructed,
toward the north. They meet like two warriors, and the wild mixing of these
contrasting air masses makes our Midwest weather famous for its violence and
changes. I (RNB) flew around the world looking for bad weather while doing
weather research and never found any worse than in the Midwest of the United
States. There’s not a geographic air-mass flow setup quite like it.
In that first look at the weather map, we should notice the isobar trajectory and
learn from where it brings the air and what that air is like—cold, hot, dry, or wet
—and how large an area it has crossed that will modify it. The map on page 45
shows some features of a weather map in relation to the isobars. Notice the flow
on the east side of the low. The air is coming from the Gulf region and will put
warm, humid, sticky air over the eastern part of the country, with thunderstorms,
too. Study how the isobars on various parts of the map show where the air has
come from: the Gulf, warm and humid; central Canada—called Polar Continental
—cold and unstable, bouncy, but good visibility. When inspecting any weather
map, be extra wary when the wind flow pattern brings the air from ocean areas or
large bodies of water—West Coast, East Coast, Gulf of Mexico, Great Lakes—
and be watchful if you’re flying abroad, especially Europe or other parts of the
world which have maritime surroundings. Oceans, large bodies of water, and in a
micro-sense, even rivers, bring moisture. And moisture makes weather. (The Seine
River wraps around the east end of Orly Field at Paris, France. Early-morning fog
rising from the river often makes the east end of Runway 26 zero-zero, with the
west end of the airport ceiling and visibility unlimited [CAVU].)
Wind flows and isobars above influence of surface.
Where the hot, cold, and wet or dry air comes from to make our weather.
Drift vs. high- and low-pressure areas in the Northern Hemisphere; reversed in
the Southern Hemisphere.
Isobars connect points of equal barometric pressure, but they also show the
wind direction, because the wind parallels the isobars to make a picture of the
wind direction pattern. The closeness of the isobars tells the wind velocity; if they
are tight—close together—it will be a windy day.
If the flight path is toward a lower pressure, drift will be right, requiring a left
correction. Toward a higher pressure, drift will be left, requiring a right correction.
This can be picked up with altimeter settings; if the setting ahead is higher, then
you’ll be drifting left, and the opposite toward a lower altimeter setting. Of
course, in the southern hemisphere, it’s all reversed.
So it is the winds, along the isobars, that brings air masses to us. Arguments
about what causes the wind and how all this movement gets started and pushed
really don’t matter to pilots; we simply know that the wind-isobar pattern is
transporting air and it will mix, heat, cool, climb, or get pushed to manufacture
the weather.
What else do we look at when we see a weather map? There are two basic
items: the pressure systems and the fronts. We look at them and visualize their
movements and possible changes in relation to our flight path.
Unfortunately, sometimes we overlook the pressure systems to study the
fronts. We are apt to forget that a high-pressure area, sometimes called a ridge, is
also a system, and not just a place between two lows. A high can often put out a
lot of bad weather, and we ought to look at it with that in mind.
Where the lows are is also important. The fronts are a part of them and move
or trail along as the low does. It is important to realize how far we will be from the
center of the low. A long cold front coming out of a low in Canada and trailing
back to the southwest has different weather in different places along its length.
The weather at Burlington, Vermont, will be different from the weather at
Harrisburg, Pennsylvania, and that will be different from the weather at
Greensboro, North Carolina. Each front has its own character, and the weather is
always different as we progress along a front. There can be a lot of weather along
a front or none at all—such as a dry front. Sometimes the weather can be ahead of
a front or behind it, all of which means you have to study the big picture plus each
front’s characteristics on sequential weather reports.
Weather is more intense near the low’s center. In winter, the ice is heaviest, the
cloud masses thicker, more confusing, and more difficult to top or fly between; in
summer, the thunderstorms are wilder. If the flight path will be near a low center,
we can be assured that things will be “interesting.”
The frontal systems of a low are well known: a warm front, which generally
moves south to north; a cold front, which moves northwest to southeast; and, as
the low gets older, an occluded front, which rotates backward around the low. If
the low moves, so do the fronts. If it keeps moving, its movement is easy to
forecast, and a pilot will notice that things are working out as advertised. There
are stationary fronts, too, which are what the name says—fronts that don’t move.
They bring messy weather of fog and reduced visibility and, in summer,
thunderstorms on a sporadic basis. These storms are difficult to see due to haze,
fog, and cloud layers. Stationary fronts aren’t violent like fast-moving cold fronts,
but they can cause problems due to low visibilities, especially at night, as well as
early and late in the day. The thunderstorms, once formed, can be tough.
Stationary fronts make a meteorologist’s day trying, because it’s very difficult to
say when the front will move or whether it will just sit there.
Watch the Slow Lows
Lows that slow down are the nasties that really ruin a forecast. There isn’t
anything more difficult to figure out than a stalled front. If a cold front was
supposed to go right through the East Coast but instead slows down and stops in
the New York area, things go to pieces. Instead of clearing, the skies remain
cloudy; wind hangs limply around the southerly quadrant, getting over to the
southeast perhaps, which can cause fog and low ceilings to prevail. With such a
situation, a kink may develop on the stalled front, a wave may form, and a new
low-pressure area may move up along the coast, following the stalled front’s line
and putting out a lot of weather.
What this means is that if a forecast calls for frontal passage at 20:00 hours,
but the front hasn’t gone through by 21:00, it’s time to be suspicious. Actually, to
prevent surprise, a good weather watcher will check a front’s movement as it
crosses the country, noting whether it passes other stations on schedule. This way,
a slowing or accelerating tendency can be discovered in advance. Which proves
the importance of watching past weather to see how things have been acting.
Sometimes past weather reports can be as important as current ones.
Again, wind is important. If it doesn’t shift as expected, or its velocity
changes, the wind has become a warning sign that something different is
happening. Winds picking up generally mean things are beginning to move,
probably getting wilder; the rain or snow will be heavier and the air more
turbulent. The good part is that the front is on the move and finally will pass, but
first there is the battle as it engulfs us.
If the winds slow down in our frontal system, we can worry about very low
ceilings and visibilities—perhaps lower than one can land in, at this stage of
weather-flying art. Also, the low ceilings and visibilities can extend over a wide
area. Depressingly, the slack winds are also a clue that bad conditions will prevail
for a lengthy time.
The Wind Speed Tells a Story
The difference between high winds and low winds and the resulting weather is
experienced by pilots leaving the United States for northern Europe in the winter,
a time when Europe has much fog. If winds are slack and there is little pressure
movement, pilots worry and take lots of fuel, but if a low-pressure area is
approaching the west coast of France, and Paris is forecasting 300 feet with rain
and gusty winds, pilots are quite happy and fly off without much concern; there
will be enough ceiling and visibility to get in.
We become extra wary in slack winds and bad weather if we have one of the
following: an airport near any body of water, such as rivers, lakes, oceans,
swamps; flight late in the day toward darkness; flight toward mountainous areas;
flight to a place where there is a lot of moisture on the ground from snow cover in
relatively high temperatures, which creates a surefire fog condition; ground
soaked by previous rain; and flight toward cities and heavy industrial areas.
Highs Are Not Always Nice
As we visualize a low-pressure area, we often have a dark and foreboding feeling;
thinking of a high brings sweetness and light and a feeling of well-being. As we
said before, it’s not necessarily so. Highs contain, on occasion, fog, ice,
thunderstorms, strong winds, turbulence, and low clouds. Highs also bring things
we may not worry about directly but should, such as high temperatures that affect
our performance or, in winter, very low temperatures that make an altimeter
indicate higher than it should. A high has all of these things, and many of them
depend on where a low ends and a high begins.
Our low ceilings and poor visibility in snow over the Allegheny Mountains
come with a northwest wind, which we think of as the front of a high, although
you might call it the back of a low. The unstable air that a high brings to western
Pennsylvania will build a cloud deck in winter that often extends as far west as St.
Louis. On the mountaintops to the east, the ceiling and visibility will be zero;
farther west, where the air is older and modified, the tops will be lower and the
bases higher. The instrument pilot will have a delightful trip on top, despite
battling some degree of ice getting up there and then getting down again; VFR,
it’s hazardous, and across the mountains impossible. Some of our wildest
turbulence can be found in a high where strong westerly winds flow over a
mountain range and cause standing waves—also known as mountain waves.
Air-mass thunderstorms occur in highs. Most of them are scattered and easy to
detour around, but a single thunderstorm becomes a major problem if it’s sitting
right over the destination airport. To make it confusing, air-mass thunderstorms
occasionally line up and, for a while, give the appearance of a front.
The location where the back of a low and the front of a high meet is an
important place. We tend to think that when the cold front has passed, the low is
gone, and we’re now in a high, which means fair weather. Well, it isn’t always so,
because the northwesterly flow on the front side of a vigorous high may be
pumping in wet, cold, unstable air that’s often a continuation of the low and its
messy weather.
Highs, like lows, move, and when we see a high on a weather map that gives
good weather, it’s worth visualizing that it is in motion and will depart. Then,
what is behind it, such as a new low, will be moving in to take its place.
High-pressure areas are often fog generators. The quiet, clear air near the
high’s center will cool at night, by radiation, to its dewpoint; low land and valley
areas may well be fogged in from early evening until after sunrise. How early,
how late, and how much depends on the season of the year and how long the high
has lingered over the area. Be especially wary of snow-covered ground with air
temperatures below, but not too far from 0 degrees C. The air above the snow
becomes saturated, and as the air cools with darkness, the dewpoint is easily
reached, and dense fog forms to stay socked in for a long time.
At certain times, Northern Europe is a great fog generator, because in the fall a
high settles over it and often stays for many days. (It’s also one reason why
touring in Europe is best in late September and October—no rain.) But the flat
high brings nighttime fog, and as the days become shorter, the fog burns off later
and later in the day. In October, fog forms in the predawn morning and burns off
by 9 a.m. or so, but by December, it forms near midnight and may not burn off
until noon. Some days it never burns off, and I (RNB) once sat in Paris for five
December days waiting for takeoff minimums! No particular hardship.
So, while we’re sitting in the middle of a tranquil high, airplanes are having a
difficult time landing and may divert to other European airports that offer better
visibility. Many trips to Europe during these fall and winter highs gives their
share of approaches below 400 meters visibility and some, at this writing, to 75
meter minimums for automatic, Category III landings. (Aviation minimums are
measured in either meters or feet, usually depending on country of use.) However,
when flying any approach to these stable but foggy conditions, a good aspect is
that in such flat highs the winds are calm or light; there wouldn’t be fog
otherwise. So whether automatic approaches or hand-flown to higher minimums,
these instrument approaches are easy to fly because there isn’t any drift or shear.
Europe is a prominent example, but these conditions have similar catalysts all
over the world.
The back side of a high—or we could call it the front of a low—has southerly
wind flow that kills off the probability of fog, because the air is warmer, doesn’t
cool off as much at night, and is moving. This inflow of warmer, moister air is
where the afternoon air-mass thunderstorms develop. And this air, moving from
the south, runs up over the back side of the colder dome of high pressure and
begins the process of the warm front for the next low-pressure area. Milky, high
cirrus clouds that dull sunshine tell us, in an upward glance, that this process has
begun.
So high-pressure areas need serious attention, too; what’s the wind, how old is
the high, are we flying in its front, center, or back? It’s all important.
Look Up
We are apt to only think of the surface map when, really, that isn’t where we fly.
Fortunately there are maps drawn for where we do fly, in the sky above. These are
often overlooked, and they should not be.
They show wind patterns, velocities, and temperatures at different flight
levels. They aren’t listed as altitude maps, but as pressure-level charts expressed
in millibars (mb). (Actually, millibars as a name has been changed to
hectopascals, which is used in altimeter settings, except for the United States,
where we’re still using inches of mercury. However, reference to upper air charts
has stuck with millibars.) Sounds complicated, but it isn’t, and all we need to
think about is these millibar levels as altitudes. These charts of various levels start
at 850 mb, which is roughly 5,000 feet. So, if 5,000 feet is where we fly, then a
study of the 850-mb chart will give a more realistic picture of what the winds are
and what’s going on up there.
These pressure charts are made for:
mb
feet
850
700
500
300
250
200
150
5,000
10,000
18,000
30,000
35,000
39,000
45,000
There are higher charts for 100 mb and 50 mb, but they are not as readily
available. Probably it is because we don’t fly up there, especially with the sad
ending of that being the relm of the supersonic Concorde, but alas, some very
high-end corporate aircrafts are sneaking up that way, let alone some spooky
aircraft.
The altitudes are approximate, because the maps actually show at what level,
in meters, we find 850 mb, or whatever. So the charts, if viewed sideways, would
undulate as the pressure levels do, reflecting lows and highs.
All we’re doing in this little exercise is showing how the millibar-level charts
relate to altitude and saying that if we’re flying near 10,000 feet, we should study
the 700-mb chart and others for other altitudes.
The locations of highs and lows are different aloft than on the surface. At high
altitudes, one may not even see a low, because it’s all down underneath, and the
200-mb chart, 39,000 feet, may have the isobars in a straight line, with the low
nowhere in sight. However, if it does show up at the 200-mb level, you can be
sure it’s a lulu!
The sequence of charts starting on the next page shows the changes between
the surface and 300 mb. The surface chart has a deep low on the Canadian border
west of Lake Superior. At 700 mb, 10,000 feet, we see the strong wind gradient
on the south and southeast side. At 500 mb, 18,000 feet, the low isn’t as intense,
and the isobars start to become more west-easterly. At 300 mb, 30,000 feet, the
intense, tight circulation has smoothed out and started to join the zonal west-east
flow. Most of the action is down low, and the 30,000-foot-plus jet airplanes will
have little weather beyond ice-crystal clouds and probably some light turbulence.
The charts illustrated here were drawn from actual charts for the same day and
time.
Surface chart, beginning a series of four mb charts—same day, same time,
different levels. These are available via the AWC and ADDS websites, and other
sources.
According to the 700-mb chart, if we were flying from Seattle toward San
Diego, we’d have a constant left drift, because we would be flying toward a high
and would require a plus drift correction, 3 although not much, because the winds
are light along that route. We can judge the wind velocity by the isobars or the
barbed arrows on the chart.
Another point is that the winds at the 500-mb height tend to direct our surface
weather movement. In other words, looking at those highs, lows and the front, we
want to know where they’re heading, so a look at the 500-mb chart can give
direction to our surface weather map.
What we’re trying to get across is that those upper-level charts are very
important, and not enough use is made of them. We should always consider which
chart to concentrate on in relation to the airplane we’re flying: If it’s a small,
single-engine we’ll look at the 850- and 700-mb charts, the charts up to 10,000
feet. For a turboprop or turbocharged piston aircraft, the 500 mb is the interesting
one, because we’ll fly in the vicinity of 18,000 feet, although some of these
airplanes are getting up above 30,000 feet. In a pure jet it is 300 mb and up. Of
course, we take a glance at them all to see which way the lows are leaning, how
deep they are, and what’s going on at other levels. Again, these charts are
important, because that’s where we’re flying, and we should know what’s going
on up there.
700-mb analysis height/temperature (about 10,000 feet).
500-mb analysis height/temperature (about 18,000 feet).
300-mb analysis height/temperature (about 30,000 feet).
A Meteorologist’s Big Picture from the Web
In previous chapter, we mentioned how beneficial it can be to have a
meteorologist’s opinion of the weather. We also mentioned today’s challenges in
getting access to various NWS offices and an audience with one of their
meteorologists; again, not of their choice but that of bureaucratic decision.
However, there is a computer-accessible product—a forecast—that we feel not
only gives a good meteorologist’s view of the big picture, but is often pretty close
to having that meteorologist’s personal opinion of the weather which we’ve
harped on as being so helpful.
Called the Area Forecast Discussion (AFD ), this is a plain language forecast
that is produced at each individual NWS office, by their in-house meteorologists.
(This is not to be confused with the aviation area forecast (FA). Also, since the
acronym A/FD also refers to the Airport/Facilities Directory, in this writing we’ll
refer to the area forecast discussion as “forecast discussion”; a term often used for
it.) They offer not just a valuable meteorological discussion of the weather as
forecast but also the why; this opens up subtle little inputs of phenomena that are
causing the weather, giving us a better picture of the day’s sky. Often there is also
comment on why the forecast might vary, which gives us that “IF” situation so
important to aviation weather.
The forecast discussion is usually interspersed with some technical
meteorological jargon, but one can pretty easily pick out the meaningful flow of
the forecast. At the same time, should we wish to learn more of weather, we can
go into the NWS glossary and other sources to seek definitions of and information
regarding terms unfamiliar to us—great weather education. A requirement of the
forecast discussion criteria is to end with an aviation specific forecast, which is
again written in mostly plain language, save reference to some familiar aviation
terms and abbreviations.
If we want to review each forecast discussion over our path of a flight, we
need to call up each weather service’s individual forecast discussion along the
route. Their forecast coverages are sometimes quite broad, so unless we’re flying
a long-range flight, this isn’t too extensive a task. Also, some forecast discussions
can be rather brief, often in areas where the weather is very good and
straightforward. However, with the requirement for an aviation segment, we find
that portion sometimes of more substance than the main body of the forecast,
which is obviously to any pilot’s benefit.
The area forecast discussion, in its total form, is not on the main menu of the
AWC/ADDS Web site, which makes accessing this helpful resource unfortunately
complex. However, typing in the city you wish to access in the upper left of the
site will bring up that city’s weather page, and the forecast discussion has a blue
link on the right side over a map of the respective NWS’s location. Another source
is through the website of the NWS Southern Region Headquarters, which gives a
“click-on” map of the United States that allows us to access whatever NWS office
we wish. We can access just the aviation portion of any offices forecast discussion
through the AWC/ADDS Web site. In the blue column on the left, with numerous
weather data subjects, select “Forecast,” click the words “TAF Forecast
Discussion” and you’ll find a map similar to that mentioned above, but again, this
one only sources the aviation portion of each weather offices forecast discussion.
Lastly, we can also type “area forecast discussion” in the AWC or ADDS website
source box.
It’s a lot of stuff to just get a forecast, but sometimes that’s what we have to
do in aviation. Cutting corners doesn’t work well in the business; and once we’re
in the swing of it we’ll be glad we took the time.
1 . “Chart” and “map”: For the purposes of our writing, this refers to the same
thing, as pertaining to graphic weather display, such as “surface weather map”
or “500 mb upper air chart.”
2 . A “lightning detection system” displays thunderstorm activity by registering
lightning discharge. For further information, see Chapter 15: Thunderstorms .
3 . In navigation, when you change heading clockwise, you increase your number
of degrees, hence a positive or “plus” correction. The opposite direction,
counterclockwise, decreases heading degrees, hence a “minus” correction.
5
Getting That Weather Information
When we have the synoptic and map well in mind, remembering that the upper air
charts are part of the synoptic, the next step is to study the weather in detail. We
want to know what’s actually going on: the actuals (METARs), upper-level charts,
satellite images, radar and radar summary charts, pilot reports, and forecasts.
There is more, too. We also need to understand where to find this weather
information, how it works, and how to keep up with its changes.
Always Learning Where and How
As was said previously, there is constant change in the weather dissemination
process, but in this day and age, we occasionally go beyond just modifying known
products and methods. Today, we are seeing totally different concepts in these
areas that not only need to be understood technically, but they also bring new
concepts to how we gather weather information and conduct our flying. An
example is NEXRAD. It changed the whole way we looked at convective weather,
especially having equipment to detect the phenomena in the simplest of aircraft;
overall a superb addition to aviation. However, with it came the need to
understand not only what the service provided, but also learn how to use it
effectively and safely. All said and done, it adds another layer in defining our
weather flying. Most importantly, with such influential new products, if not
properly understood and used, they can actually increase hazards to our flying.
So, it is necessary to ferret through all this weather information, finding out
what’s a change in an old product or what’s something totally new that requires
extensive study and practice of usage. Either way, when these issues come around
to weather services and all they offer, we need to frequently review what changes
have been made and the extent to which we need to study and understand these
changes.
To this end, there are publications that are important in both the regulatory and
operational arenas. The Aeronautical Information Manual (AIM ), under the
umbrella of the FAA, is a definitive guide of how our aviation system in the
United States operates and how we as pilots must function within it. The AIM is
not a regulation, but it’s important that we consider it as a common operational
practice so that as an aviation community we function with some sense of
standardization. The AIM, of course, includes weather (meteorology in their term)
which falls under Chapter 7 , interestingly titled “Safety of Flight.” Of course we
cannot forget the all-important Federal Aviation Regulations (FARs ). Both the
AIM and the FARs are regularly revised, so keeping up with these changes is
important. If we consult an FSS briefer or NWS meteorologist, we can learn how
these changes fit into the system, which of course helps our understanding. Also,
regular recurrent training with an up-to-date instructor can keep us aware of
changes.
Reading aviation magazines for a general idea of what’s new, as well as what’s
on the horizon with coming technology or changes to regulations and procedures,
is not only interesting, but almost a necessity. With that, we refer readers to the
FAA’s magazine Aviation Safety Briefing , (either hard copy subscription or online via the FAA’s website www.faa.gov ), as a neutral complement to the many
fine publications available. The NWS AWC website offers access to an
instructional newsletter called The Front , and a Web-based tutorial on many
weather subjects, called Jetstream . We highly recommend them. Also,
memberships with national and international aviation organizations are helpful
and important, with most offering excellent publications.
Saved for last in this subject, but of great importance, is the concept that we
have reached a stage of aviation technology and operation, and how weather is
woven into the process, that needs more formal education. Arguably, we are late
in this area. It would seem a solution is more proactive dissemination of weather
education, both theory and how we use it, as well as equipment-and productspecific education. There are quite a few competent sources in this direction—
some classroom-based and others via electronic media—that offer excellent and
necessary education towards the flying environment, as well as increasingly
complex aircraft and equipment.
In summary: the responsibility for keeping current in all aspects of the flying
world cannot be taken lightly. Those who have only a shallow knowledge will
eventually find themselves in trouble.
Some Extra Sources
With the advent of computerized weather, we have seen continued improvements
of current weather products, as well as new efforts. One thing is for sure, these
improvements and new products will just keep coming along. There are a few
products we like that are helpful for obtaining weather information, or taking a
broader look into forecasting that, until recently, were unavailable.
Center Weather Service Unit (CWSU ): This is a weather product designed to
assist the air traffic control system. It uses a map of the whole United States to
show airports that report weather data; METAR and TAF for those which do
so, and ASOS/AWOS airports as well. The airport symbol is a small “plus”
sign, and by selecting each airport with computer mouse, we can find history
of past weather observations, TAF and METARs, PIREPS, graphical history
of the past weather, Skew-T charts, and satellite images. There is also the
NWS forecast page for the city of the respective airport’s location, and on the
right side of that, we can reference the Area Forecast Discussion mentioned in
the previous chapter. Also, if we click the cursor away from an airport, the
national map will change to a more detailed map comprising that ATC center’s
area, or hit it again for even more detail in high density air traffic areas such as
New York, Los Angeles, etc.
With the CWSU map on the computer, we can check various airports along
our intended route of flight, getting instant METAR and TAF, as well as the
more in-depth details. One of these is called the TAF Tactical Decision Aid
(TAF TDA ), which is kind of an all-in-one page, as it relates to TAF and
METAR data, with a color underlay explaining how the weather relates to
conditions of VFR through Low Instrument Flight Rules (LIFR). This CWSU
page, along with a good synoptic surface weather map, is a nice big picture
overview. We can also chase around the map in a particular weather
phenomenon, learning how it affects the weather at different locations.
For more information, access the March 2010 edition of the NWS/AWC
online publication The Front . The Suggested Reading section also lists
website access for the CWSU.
Models: We hear of these products almost daily on radio and television
weather broadcasts, the latter often showing these models graphically, with
coverage usually extending over a period of days. Models are the core of
modern forecasting, along with the old-school sixth sense of sage and
experienced meteorologists. Ironically, old-school meteorologists still feel
there is a valid place for human input, versus excessive dependence on hightech instrumentation, automation, and data, which is the same argument of
old-school pilots. You have heard and will continue to hear that song as our
book proceeds.
Models are made up of immense quantities of weather-related data that are
massaged through extensive computerization. This data comes from satellites,
radars, weather balloons, surface observations, aircraft, and more. The aircraft
aspect is kind of interesting, with data of temperature, winds, and so forth
being automatically transmitted from thousands of daily commercial aircraft
operations. These models are revised frequently—sometimes hourly—which,
of course, constantly updates their accuracy. As in any forecast, the longer the
forecast period of the model, the lower the accuracy; but these things are
getting pretty darn good. There are many model products available worldwide,
which are linked through computerization. In the United States, a lot of the
modeling information is produced through another NOAA affiliate—the
National Centers for Environmental Prediction (NCEP ). We can take a look
at models ourselves, on the computer of course, which let us look into the
weather crystal ball on our own time. It’s a good education and quite
interesting.
Model Output Statistics: There is also a model product quite helpful to
weather forecasting at airports for which a TAF is not produced; it’s called
Model Output Statistics (MOS ) and is part of the Localized Aviation MOS
Program (LAMP ). This is a statistical forecast system that, as of this writing,
is worked for around 1700 airports in the United States; that’s almost three
times the number of airports that produce TAFs. MOS guidance is created
through modeling, is updated frequently, and depending on which MOS
product can reach out over 24 hours or up to a few days into the future. These
forecasts are presented differently than TAFs, in a table-like format, with
some data, such as cloud height, sky cover, visibility, and obstructions to
visibility, supplied as a coded number relating to a range of visibilities and
ceiling heights; the numbers correspond to the various visibility criteria from
LIFR through excellent VFR weather. Model Output Statistics considers
fluctuations that can occur in flight conditions, which gives us a kind of
envelope in planning our flights. Also, graphical presentation of these
forecasts, along with some probability input of the data, is also available, as
compliment to the numerical product.
These MOS forecasts are not approved primary weather product, but their data
can be quite good. Their importance is related to the fact that TAFs are only
valid for 5 statute miles around the reported airport’s center, and all else must
be covered by the rather broad area forecast. With somewhat over 600 TAF
airports, you can see there are lots of voids in individual airport weather
forecasting. If we’re flying to an airport without a TAF, after we’ve checked
the legal primary weather product of the area forecast, we can check our
supplementary product of MOS. It effectively puts a forecast into many small
airports previously without. Of course, we take it as any forecast, with that
“what if” mindset.
To learn more of MOS, its use, and how to read it, access this book’s
Suggested Reading for websites accessing both MOS data and tutorials on
how to read the data. We also recommend the June 2006 and March 2010
editions of the NWS online publication The Front .
Skew-T log-P: This product has been around from the beginning of modern
weather analysis. It is the core of reading what our atmosphere is doing, taking
a vertical look—a snapshot—of temperature and dewpoint in comparison with
the atmosphere’s pressure, which of course means altitude; all this is in
relation to a specific location on the earth. From this, we can derive where
clouds will form, meaning we can predict cloud bases and tops, as well as the
potential for phenomena such as thunderstorms, ice, fog, inversions, and so
forth. There is also very concise upper air wind information from the surface
to the troposphere. The data is displayed in a graphical, thermodynamic
diagram called a Skew-T log-P diagram, also known as a sounding chart;
there are others, but we’ll stick with the Skew-T log-P.
To get this data, meteorologists launch and track weather balloons from, at this
writing, seventy-two NWS locations in the United States let alone other
countries. The balloons, which carry a transmitting instrumentation package,
rise to upward of 100,000 feet, where they pop, after growing to the size of a
small building. A little parachute returns the well-packed instrument package,
with identification of its government status, in hopes of return and subsequent
reuse. [The voyage of the balloon and its instruments are referred to as
rawinsonde observation (RAOB ); they used to be called radiosonde .] The
data is transmitted back to the NWS facility, where today it eventually winds
up at the NCEP and is analyzed and presented in the Skew-T log-P diagram.
Before the computer world, this data and the diagrams, along with the related
weather forecasts from this data, were totally derived from balloon data. Now,
however, the balloon data is supplemented by other sources, including the
many data points from aircraft—mostly airliners—that transmit constantly
updated temperature, altitude, and wind data through their advanced avionics.
Also, satellites are looking down on us, reading similar data. All said and
done, this relates to weather modeling and the ability to create Skew-T log-P
information, and forecast data like the above-mentioned MOS forecasts, for
those 1,700 airports and locations. With this wider variety of Skew-T log-P
data, we can supplement data such as MOS, giving us a look at things like
localized thunderstorm potential or cloud formation as it relates to an airport
and its surrounding terrain. Another help could be seeing cloud and belowfreezing temperatures at our altitudes of flight; we can then consider icing
conditions, and if freezing temperatures reach the ground, we know we’ll
potentially be trapped with the phenomenon, with no altitude where we can
escape it before reaching the ground! Skew-T log-P wind data is of close
altitude spread, and as displayed on the chart, easily allows us to spot wind
velocity and direction changes. That’s where turbulence and other wind
weather–related issues can form. This is tighter information than from winds
aloft forecast data, as that product can spread as much as 3,000 feet and over
six hours; a lot can happen in those voids that Skew-T’s more current data can
show us. And, if you’re a sailplane pilot, we can predict thermal height and
strengths or tell how high we need to climb in our powered aircraft in order to
top a good soaring day’s thermal turbulence. There is plenty more. Oh! where
did that quirky little name “Skew-T log-P” come from? Well, the story goes
that the temperature (T) is plotted upon reference lines “skewed” at an angle,
and the pressure (P) plot is not linear, instead somewhat logarithmic, hence
“log.”
A good start to learning more of Skew-T is the February 2004 issue of the
NWS/AWC online publication The Front . There are also relevant website
addresses in this book’s Suggested Reading section.
Once we get into the swing of it, MODELS, CWSU, MOS, and Skew-T log-P
can add an interesting, helpful and enjoyable aspect to curiosity of the sky.
Refer to the Suggested Reading section at this book’s end for further resources
on learning about and using these very interesting and helpful resources.
National Oceanic and Atmospheric Administration (NOAA) Weather Radio:
Lastly, we’ll take a trip back to low-tech, following that philosophy of not
chucking out the past just because of what’s new. If we’re not glued to a
computer or otherwise and want a feel for the day’s weather, most of us
probably recall the NOAA network of radio stations, which continually
broadcast local weather on frequencies from 162.40 to 162.55 megahertz
(MHz). These are not specifically aviation oriented but give a good picture of
the weather over an area of roughly 100 miles. They are changed three times a
day, except if there is an emergency or sudden adverse weather development,
when they’re changed immediately. There are about 1,000 stations around the
United States, so most of the country is covered, and about 90 percent of the
nation’s population is within range.
Special receivers, some of which have an alarm that warns of any imminent
dangerous weather, can be purchased inexpensively. These frequencies are
also located on numerous hand-held aviation communication radios. There is
one at the local airport where we fly, and it’s paid for itself. With no one
staring at a computer and its radar, the alarm alerted us on more than one
warm summer afternoon to an approaching line squall. There was mad rush to
tie down aircraft, and the warning probably prevented aircraft damage as the
wild wind and rain rushed in.
Older technology, yes, but it works, prevents problems, and if you have ever
been in a real weather emergency without other communications and dead
computer and smart device batteries, this will give us timely, accurate
information. Besides, like TV weather, if we want to get a feel for the day’s
weather, it’s a nice way to connect while we run around our home, getting the
day started or whatever.
A Skew-T sounding chart for Cincinnati Covington Airport (CVG) in northern
Kentucky, just south of the Ohio River. Of the many lines are the ones from lower
left to upper right—the “skewed” temperature lines, representing 10-degree
temperature differences. The vertical of the chart is non-linear altitude in
millibars left and feet on the right (hidden by wind flags). Wind is the graph on the
right, showing typical wind arrows and velocity flags. Upper left of Skew-T log-P
is wind path and velocity as compass orientation. The two squiggly lines in the
middle of the graph are dewpoint on the left and temperature on the right. The
temperature line going left is a decrease; going right it is an increase—an
inversion. Other lines represent things like lapse rate, etc. The chart’s top legend
says type of sounding, date, and time. Very important is noting where the sounding
was taken; along the top legend we read “8.8 miles at 124° from CVG.” This can
be an issue if around mountains, bodies of water, etc. Ground elevation is about
830 feet, and where the temperature and dewpoint lines are close or meet, we can
expect clouds if there’s enough moisture. First at about 2000 feet above ground
then again around 19,000 feet. At the same time, the METAR had a few clouds at
1,600 feet and overcast at 18,000 feet. A picture’s worth of many words.
No One Said It Was Easy
It’s difficult to sort out the mass of acronyms, contractions, and coded information
that invariably come with weather’s extensive resources and diverse amounts of
information. Also challenging are the different and overlapping services. There are
many references to where we can hear weather on aircraft radios and find it on
electronic access, both on the ground and airborne, while the sheer mass of data
compounds the muddle. Here again, we recommend the AIM, this time the
glossary and index, and the publication Aviation Weather Services AC 00-45G .
The previously mentioned NWS/AWC website will also lead us to many tutorials
and their own glossaries of terms. And the FAA website also addresses weather
services, including, as mentioned in previous chapter, that of the ASOS/AWOS
stations: where they are and their frequencies and phone numbers, along with the
FAA’s airport facilities directory, which we can purchase with a subscription.
With these publications and Web pages supplied by the NWS, FAA, and NOAA
—the government—we’re dealing with aviation weather’s primary source of data
in the United States. Also, with Canada our close neighbor, we should not forget
their services, Nav Canada .
Regardless of all these problems, the need for weather information is still
there, and when you climb in an airplane and prepare to fly, it isn’t any different
from the way it was when things were simple. It is important to mentally set aside
the “modern” methods of communication—the confusion of frequencies,
telephones, computerized sources, and mass of data—to clear your mind and
focus on the gut things that count, like fog, ice, thunderstorms, ceilings,
visibilities, wind, turbulence … the lot, no matter how it’s packaged. You must dig
for information and ask questions until your mind has a clear picture of what’s out
there and how it may or may not act.
How do we sort it out? As we‘ve mentioned, FSSs give briefings of present
weather, forecasts, a condensed synoptic, winds aloft, and any weather warnings
in force. The NWS offices can give that important meteorologist’s opinion we
talked about. Now, with electronically accessible weather, we can get everything
we want, if we know where to get it, what to get, and what it means. However, as
also said before, the weather given to the pilot presents a picture of weather
straight ahead, down the course line. It tells little of the action off course, where
fronts or other kinds of weather may be in motion to eventually create problems
along our course.
Hired Help
There are private meteorological services, where we pay for the service. These
private services, however, are not just meteorological. They are full-service,
flight-organizing, and in some cases dispatching services. With today’s
complexity of aviation, especially international flying, they will file flight plans
fitted to our airplanes, get all the international paperwork and clearances
organized, and arrange for the all-important fuel, sometimes at special bulk rates,
as well as many ground needs. However, back to weather, they can plug us right
in to a meteorologist we can talk with about the weather and our flight.
These services are excellent, especially in packaging the whole works, a big
help to busy flight operations with complex demands. Also, when we think of the
reduced availability of weather briefers and meteorologists, these organization’s
private meteorologists are appreciated professional help. If you are going to use
one of these services, it is important to check that the service has meteorologists
who interpret the data, massage it, and talk to you about it—just like the good old
days. Without that part of it, it’s just a streamlined way of getting the data we can
get ourselves; save, of course, the helpful organization of paperwork and facility
needs. Of course, these private services cost money, and the average private
airplane owner isn’t likely to add the extra costs when the government or our
favorite electronic gadget supplies it. Interestingly, even pilots flying very heady
aircraft, such as high-end corporate jets, can use their personal electronic devices
with flight-planning applications to brief a flight and file the flight plan. If their
operations are not complex, this is an astounding state of our industry. One
concern, however, is that we hope this self-service ability to get our weather
briefings and plan flights won’t inspire some aviation-unaware officials to reduce
quality of the government weather dissemination, making the methods more
impersonal, of lesser quality, and maybe less accessible, and the whole system
less safe.
However we do it, private service, computer access, FSS, NWS, or what have
you, the game is the same. Pilots must ask the right questions, whether to a briefer
or to ourselves, to have the proper picture and knowledge, in order to make the
correct decisions to fly (or not) the weather.
Opening Remarks to the FSS—and Ourselves
When FSS and NWS were the only weather show in town, the business had a
colloquial feel, especially if you had an FSS at the local airport. Often, these
facilities were a Saturday morning meeting place talking about weather, flying,
and all that goes with it; we learned a lot. However, when away from our local
FSS, especially when calling another while on the road, the key was not to glide
into the office or pick up the phone and simply say, “Hi y’all, how’s it look to
LA?” If we did, many briefers would tell us, just as unceremoniously, “It’s VFR”
or “It’s not very good” or whatever. To get the weather we need, VFR or IFR, it
was, and still is, very important to open the conversation with a professional
sounding sequence of the appropriate information we need for a briefing. In this
day and age there is a standard sequence of information the FSS likes in proper
order; the big reason is for conformance of how they enter it into their computer,
from which comes our briefing. It speeds things up for both ourselves and the
FSS. Now the briefer knows what’s needed, not just of the flight, but with some
sense of our limits as a pilot and aircraft.
So the sequence is:
•
•
•
•
•
•
•
•
•
Type of flight: VFR or IFR
Aircraft identification or our name
Aircraft type
Departure point
Estimated time of departure
Altitude
Route-of-flight
Destination
Estimated time enroute
Now we pick up the phone and it might go like this: “We’d like a standard
briefing for a VFR flight. Our aircraft is N-whatever, a Cessna 182, and we’re
departing from Montpelier, Vermont (KMPV) at an estimated 1500Z, cruising at
6,500 feet and whatever route-of-flight to Elmira, New York (KELM). We’re
estimating one hour and forty-five minutes enroute.”
It’s important to say and spell the airport identifiers, as with the centralized
FSS system we might be talking to a specialist in say California; it’s a big
country! On the other hand, we can also request a specialist familiar with, in this
case, the New England area, who if available will have better grasp of local
weather issues, easing the briefing for both them and us. Also, the “Z” after 1500
means “Zulu Time,” the same as Coordinated Universal Time (UTC) which used
to be called Greenwich Mean Time (GMT).
So we have asked for the works, which is what we should be asking for, and
now it’s time to pay close attention to the briefing. This learned approach on our
part is professional, the briefer knows we’re serious and that we want a good
picture of what’s out there—from synoptic to sigmet.
Doing it offhandedly and informally can invite an offhanded and informal
response and, for those very few briefers who might like to tell us how to fly, a
chance to editorialize rather than detail the weather. Again, this is most likely an
issue of the past, but if it happens we might find the pilot departing with a sketchy
idea of what’s really out there. It may sound stuffy, but this is the time to be
formal and serious!
Since today’s FSS briefings are over the telephone, we again mention three
thoughts to make it easier:
1. Check a computer, personal electronic device, TV, or even newspaper weather
map to know the general weather setup—the synopsis—before our call to the
FSS.
2. We shouldn’t be afraid to ask the briefer to repeat things.
3. Train ourselves to write down weather symbols so we’re using a sort of
shorthand to copy what’s being said.
Synoptic Again
So where do we start? We start with our old friend the synoptic, no matter where
or how we get it. If we have a good mental concept of this big picture, we’ll know
whether there are fronts on the move and troublesome weather stirring for our
flight. We are trying to learn what to be wary of—weather speeding up, slowing,
stalling, and changing to lower ceilings for landing. Possibly thunderstorms or ice
are developing, then again they might already be in the picture—things that will
seriously harass our flight. An important point is that if our synoptic homework
was done well, we are in a position to ask, after the routine briefing, some
searching questions about off-course weather that might worm its way onto route,
making the day difficult. Where is the front that’s not scheduled to be over the
route until after we’ve landed? Any chance it’s moving faster—fast enough to
clobber the route while we are flying over it? How about those thunderstorms
forecast for tonight—might they mature in the late afternoon, about the time
we’re expecting to reach our destination? These are the important questions, and
the protective intelligence to ask them comes from what we learn by scrutinizing
the synoptic in advance.
Look Ahead
Much in tune with the above is the wisdom, when getting a briefing, of asking for
future forecasts—forecasts for the next period after our estimated time of arrival
(ETA)—so we can keep an eye and ear out for the possibility of weather moving
or developing sooner and giving us trouble. Such inquisitiveness backs up the
basic fact that one should always approach weather forecasts with a certain
amount of skepticism.
The Real Thing
Now on to the actual weather reports—what is it really doing? These should be
studied along the entire route, not just for the airport of destination, but for each
reporting point along the way, so we’ll know what to expect en route. This is
especially important for the VFR pilot, and even more important if there is rough
terrain—mountains—along the way. The higher terrain will have lower ceilings
and visibilities under conditions of poor weather. A scrutiny of the reports will
give an idea of what to expect.
There’s nothing sloppier or more hazardous than the pilot who simply asks: “Is
it VFR?” and, armed with that, and perhaps winds aloft, charges off into the blue,
flying from a position of ignorance.
The study of the actual reports for airports along, behind, ahead, and to the
side of the route for the latest and past few hours, is important for learning how
the weather has been acting. To be thorough, a past forecast should also be looked
over and correlated with the actual weather sequences (METAR) to see how the
weather has been, compared with what it was supposed to have been; this is far
less difficult to obtain than in years past.
When in the air, the weather we’re flying should be related to each hourly
report, which should be gathered routinely and religiously while flying. The past
reports, compared with the new hourlies, can give a strong insight to weather
changing, developing, deteriorating, or, happily, getting better. This constant
study, while flying, of the latest actual weather reports cannot be overemphasized.
Equally important is the wily pondering of what’s changing, which sends signals
that not all’s well in the sky. The key point here is that the actual reports should be
gathered each hour we fly, then compared with the past hour’s report and the
forecast.
Obviously, if we’re flying across a big high and it is CAVU all over, we don’t
have to check weather every hour, but the more inclement the weather, the more
we have to be on top of it. It doesn’t hurt, on that CAVU day, to gather a report or
two, confirming it’s really staying CAVU. There is always the possibility for
surprises, and if the weather is that good, there isn’t much to do anyway.
It’s only natural that our major attention is toward the destination, but there’s
much to be learned about development along the way, especially if thunderstorms
are in the forecast, as well as ice and turbulence. So again, attention needs to be
given to reports for stations along the route as well as the airport we’re headed for.
Constantly, however, we check the destination’s hourly actuals—METARS—
to be certain the weather is holding up and not starting a downhill slide of ceiling
and visibility. There’s little or no excuse for a pilot to arrive over the destination
airport and be “surprised” by below-limit conditions.
Actual weather reports, either the hourly METARs or Special Weather Reports
(SPECI), which are issued when there is significant weather change between the
usual hourly observations, are tremendously important. Because weather
forecasting is not exact, and probably never will be, we need the actual reports to
know how the forecasts are doing—is the weather as promised or something
different?
The actual METAR is the point of truth. All the forecast charts, maps, and
reports we’ve seen are not real . They are only estimates of what will happen, and
the radar charts, satellite images, are all what was, not what is, when we’ve seen
them. Even data link weather graphics during flight are instantaneous pictures of
the time they were taken, and we need to verify that time. With NEXRAD we
have a time-delay issue that, as mentioned before, we’ll detail in Chapter 15 on
thunderstorms.
The METAR is the latest weather information at the moment it’s taken, but
then it can be an hour before the next one, possibly significantly different when
we arrive. Say we start an instrument approach with the weather reporting 200
feet and half a mile, within our limits, but when we get to 200 feet, the ground
doesn’t show up, and the ceiling has gone down since we started the approach.
Now what are we going to do? What we’re pointing out is that finally the flight
will be directed by the pilot in command who, we hope, understands that the real
conditions affecting the flight are what is seen and experienced, not what charts,
maps, or reports say. Now the pilot is in command, performing the best way
possible, using whatever experience and skill is in that pilot’s background, to
complete a safe flight.
But in weather, gathering these things—the synoptic picture, forecasts, and
actual reports—is the key. If this book only gets that across, it would be
worthwhile.
Many years ago, teletype sequences went west to east and south to north,
giving actual weather reports in geographical order. To check weather, one read a
tape of the reports, like the old stock market ticker tape. That was logical, because
weather moves in these directions. You could observe a front moving toward the
east as you read each station’s weather report in line. The wind would be
northwest at Kansas City, but still southwest at Columbia, Missouri, and you
knew where the cold front was—somewhere between the two stations. Or one
could see a warm front progress from south to north, graphically, because the
reporting stations followed the same path. Computers have taken over, and all this
logical order has become history. True, this has been reintroduced in graphical
computer displays, from which we want to make sure we conceptualize what’s
happening. In other words, when we see changes in weather as it progresses along
our route of flight, we ask “Why?”, in lieu of just taking it as an event. Then, of
course, there are the times we don’t have that graphical display, of which an
example is seeing computerized graphical display for briefing but not having data
link graphics in flight. We need to know how to think those weather maps, just as
we had to visualize the weather’s lay in the old teletype days.
Today, when getting our briefings, we get the actual reports for stations along
the route we’ll fly—not too far beyond or before or off course. It’s as though
we’re looking down a route wearing horse blinders. However, what is beyond the
station and moving toward it, or what’s happening with that front off to one side,
and what was the previous weather compared with the forecast? These are all
things a pilot should know. The information is available, whether we ask the FSS
briefer for it or get it ourselves electronically; then we study the setup and its
possibilities. This is necessary, and a pilot should have the discipline to do it. The
present system will tend to make the lazy pilot take the route forecast and go with
it—a good weather pilot will dig deeper.
The pilot must keep digging until satisfied that there is good and sufficient
information to tell the weather story. This can be difficult on telephone briefings,
because the person on the other end of the phone may be pushed to get on to other
briefings, as we ask for more information than the normal briefing gives. This is
rare, but can happen. They are busy, but that shouldn’t intimidate us.
Years ago, I (RNB) was talking to a briefer on the telephone about weather
from Philadelphia, Pennsylvania to Burlington, Vermont. He said it was all VFR.
But from the TV map—no computers then—I knew there was a front to the west
that could move on course if it speeded up. Asked about it, he said: “Oh, that
won’t bother you. Your route’s forecast VFR for your time period.”
Not satisfied, I started asking for actual weather reports at stations like
Buffalo, Rochester, and Harrisburg in an attempt to learn where the front really
was. The briefer became irritated and said rather strongly, “What do you want
those stations for? You’re not goin’ that way. I just told you it’s VFR!”
Although such an attitude is rare with today’s professional briefers, this
example demonstrates how people get in trouble with a sketchy picture of the
weather. That front was moving faster than forecast and did mess up the course,
and I eventually had to file IFR later in the flight. Now, what about the VFR pilot
new to the game and starting out on that briefing? Would they know enough to
land? Turn around? Run east, or press on, getting lower and lower, with less and
less visibility in mountainous country, thinking it ought to be okay because the
briefer said it would be VFR? It’s the typical setup for a weather accident by
pushing VFR too far.
This also makes the point that a pilot cannot depend on a briefing being so
accurate that the statement “It’s VFR” covers everything. Weather science isn’t
accurate enough to do that, but the tendency of the system is to make it appear as
though it is, and this means another adjustment in pilots’ thinking; they must not
allow the official-looking maps, charts, forecasts, graphics, and briefings lull them
into feeling that the statement “It’ll be VFR” is solidly accurate. Once we’re
airborne and flying through the weather, in clouds, ice, thunderstorms, fog, or
whatever, the authoritative appearance of the weather briefing quickly fades, as a
pilot combats the weather and wonders what is this phenomenon that the briefing
didn’t divulge—and what to do about it!
Preflight study and constant updating will be the pilot’s defense, as well as an
aid, when there’s a sudden discovery that the forecast—and the statement “It’ll be
VFR”—are inaccurate, with the real world different and tougher!
Of course, if we can access data-linked weather in our airplane, we can call it
up anytime, easily keeping current. Otherwise, without data link weather in flight,
a pilot should feel free to pick up the mike and ask for weather. We need to
remember that getting weather information is the pilot’s job, and nobody is going
to spoon-feed us. It is easily possible to be flying along feeling good about the
world, never realizing there is some tough stuff ahead or at the destination. This
euphoric, and dangerous, situation could exist simply because the pilot did not
assume the responsibility of keeping up with the weather.
Pilots should always remember that the route of flight or destination may have
to change with the weather. It is folly to plug along without flexibility of thought
and willingness to realize that one may have to fly differently, change route, go
IFR, divert, turn back, or even land.
This is a significant point—being flexible. The fixation of plugging toward the
destination, even though the weather has turned foul, has killed too many people.
One should be ready and willing to toss aside the idea of “getting there,” in favor
of turning away to a safe-weather airport. Important!
These problems of gathering and studying weather information, we believe,
are the genesis of more weather accidents than any other single factor. The
system, along with aircraft flaunting equipment that tempts pilots to believe they
can fly almost any weather, has seriously threatened the idea that pilots need to
make weather judgments and at times respect the fact that their original flight plan
is not going to work. As we’ve said again and again, a safe pilot must be a
weather person, too!
6
Weather Details—What They Tell Us
When we look at weather details, chances are that the first thing we’ll glance
toward will be the destination weather. What is it, VFR or IFR, and how close is it
to the legal limits? These details come mostly from actual reports like METARs
and TAFS. Graphical weather may give us a good overview, but not the finite
details of data we discuss in this chapter. So despite our marvelous world of
graphical weather, this chapter helps reinforce why we still need clever, old-school
analysis of weather reports.
It doesn’t take too much soul-searching to judge if weather is within one’s
ability and equipment. Basically, the flight can either be made VFR or it requires
IFR, and marginal weather between the two can cause trouble. If it is marginally
VFR, then the pilot had best be prepared to go IFR in case suddenly, en route, it’s
discovered that IFR has become a necessity. Trying to hang onto VFR when
things have deteriorated, and IFR weather is becoming more of a reality each
moment, is a proven method of getting into serious trouble!
VFR—Not Easy
If it’s decided VFR is going to be the way of the flight, then the pilot may have a
more difficult decision than the IFR pilot. In many respects, the VFR pilot needs
to learn more about the weather setup than the IFR pilot, because the VFR pilot
must know if the weather will remain VFR from takeoff until landing at the
destination. Sometimes this demanding decision is being made by the least
experienced pilot! Either way, experienced or not, pilots should make the decision
and not simply depend on a briefer’s statement, or our own weak briefing efforts,
that “It’s VFR all the way.”
When we do get our briefing from the FSSs, the statement that should get a
pilot’s attention and be considered seriously is the briefer saying, “VFR flight is
not recommended.” This comment creates a great deal of angst and frustration for
pilots, and not being of a fixed criterion, other than the FSS briefer feeling the
flight cannot be completed VFR or at least safely so, may sometimes be perceived
as an unnecessary legality. However, standing in the FAA’s and FSS’s shoes, we
need realize a briefer does not know our experience, how we think as pilots or
orchestrate our flying. Second, they see something potentially compromising to
the weather affecting our flight. What is most important when hearing the
comment are two things. First, the statement is not binding and the final weather
decision is still the pilot’s. Second, “VFR flight is not recommended” should be a
warning to dig even deeper for more weather information. Sometimes this will
yield nothing, but that one time we do find something sketchy with the weather
might just have been that critical event.
MVFR
The Weather Depiction Charts, as well as various forecasts, digital presentations,
and weather warnings, tell us of areas where conditions for IFR, VFR, and MVFR
can be expected. It’s the MVFR portion that should be considered very carefully.
It would be more realistic to change the label of MVFR to HVFR, which would
stand for Hazardous VFR. Why? Because that’s what it is, hazardous! MVFR is
defined as “ceiling 1,000 to 3,000 feet and/ or visibility three to five miles
inclusive.” This can be dicey weather for VFR. Poking along, down low,
especially in mountainous areas, with such reduced ceilings and/or visibilities is
asking for trouble. If precipitation is falling, then it’s much worse, because threemile visibility with rain smearing a windshield reduces what you can actually see
to far less than three miles.
Imagine. We’re nervously sneaking through this murk in mountainous
country, maybe a high peak just ahead, or in the seemingly safe flat lands, missing
awareness or warning on an electronic flight display, or that map on our lap, of a
communications tower dead ahead that reaches into the sky to a scary height.
Suddenly, it appears out of the gray world—a hazardous way of flying.
Ceilings are defined as broken to overcast clouds. This means scattered clouds
can be floating around in the falling precipitation of an MVFR area below the
1,000-to 3,000-foot ceiling. So as one flies in the rain-reduced three miles, clouds
can be encountered almost half the time, because scattered is defined as 0.1 to 0.5
sky cover. Bumping into these wispy pieces of cloud or twisting along trying to
miss them can add to the difficulty of struggling to stay VFR. You can also feel
nervous when it’s raining and lower scattered clouds are encountered, because
they most probably will increase and become broken to overcast as the moisture
of the rain raises dewpoint. Then, two things can hap-pen—the ceiling could
become well below 1,000 feet with lower visibility, and we might just get stuck
on top of this new, lower overcast (undercast) deck.
MVFR Is Not Static
An additional and very important point is that MVFR areas are not static. The
weather doesn’t stand still very often or very long. Remember, it is always in
motion! Poorer weather may be on the increase, or things may be getting better.
Either way it is tricky, because things can get worse sooner or better later than
expected. The pilot planning to fly into that MVFR area needs to be very aware of
the weather prognosis and study it carefully before the flight, learning which way
conditions for the MVFR area are forecast to change, up or down. Then, watch it
carefully in-flight by gathering weather reports and looking through the
windshield to see how the MVFR is behaving. Finally, what you see, or cannot
see ahead, is the moment of truth, the real thing, the actual weather, regardless of
the forecast.
In VFR, there is little time for decision. One cannot keep pushing in hopes it
will get better. The decision to turn and run or go IFR is now!
One can lay down a basic rule that anytime you are headed into MVFR areas,
you should be willing and able to suddenly go IFR.
There’s no way of knowing, but bets are that MVFR displayed on weather
charts has suckered people into flying areas where they should never have gone—
and never came out.
IFR—Not to Worry
The IFR pilot, and a properly flown IFR flight, doesn’t have to worry about
clouds and terrain en route, because IFR flight is at safe altitudes above it all. An
IFR pilot doesn’t fear flying in clouds—or shouldn’t. But the VFR pilot who does
not have an instrument rating has a very strong concern not to get into clouds or
areas of reduced visibility that do not give enough reference to fly the airplane and
maintain control, as well as see what’s ahead.
As said before, and because it is so important we repeat it, once a pilot looks
at the weather and decides it’s good enough, the question to be answered is: Will it
stay that way? To answer that, we look back at the big picture to see if weather is
approaching in the form of a front or if there is air-mass deterioration. On the
other hand, possibly and happily, a front has passed, indicating improvement, or
the airport is near the center of a high that affords good weather protection on both
sides. An exception may be early-morning ground fog, but that will burn off after
sunrise.
The destination, however, isn’t the only area of interest. We want to consider
alternate airports for both our destination and departure points. Either VFR or
IFR, we may want to return when still reasonably close to our takeoff point and
should know whether the departure field will be accessible. If it isn’t, then we
need an available airport where we can go in case of trouble—in the formal world
this is called a takeoff alternate. The airlines, obviously flying IFR, are required to
have a takeoff alternate if they take off when the departure airport is below
landing minimums. This is figured over a maximum allowed time with an engine
inoperative, a worst case scenario, but there are many other reasons we might
return, most all of which also apply to light aircraft; things like system failures,
doors open or more traumatic, fire. Airliners, corporate jets, and some turboprops
are very redundant designs, but privately flown lighter aircraft, not as redundant
and of freer regulation, let us decide how far to stretch things; we need to exercise
this opportunity with good sense. So, with regard to airport weather, we are
interested in destination and alternate, as well as departure and departure
alternate.
If the destination is too bad, then a pilot wants to know when it is going to
improve. What do we look at first? The forecasts. The best way of studying them
is to check them over a period of time. We check for the current time—that is,
what the forecast predicts for this very moment, then for the previous four hours,
and finally for the period of our expected arrival and a few hours after that.
Test the Forecast
With all this firmly in mind, we go to the actual sequences (METARS) and see
how the forecasts have been performing. What was the weather during the
previous four-hour period, compared to what the forecast said it would be? Then
the present—what is it actually doing compared to what the forecast says it should
be doing? Note how many special observations (SPECI) have been made.
Specials show that something is different—changing—and should act as a signal
to look closer and be alert to what the changes are. Now we have a feel for the
weather, for the kind of weather it is, and whether or not it’s acting according to
plan. If it hasn’t been acting as expected, we’d best look again at the big picture
and try to decide what’s been going on. Are the fronts moving faster or slower, are
the lows slowing, has a flow of air from the sea remained instead of turning
around? The important point is to give the weather forecasts a test and see how
they have been performing. Good forecast performance can indicate an easily
forecastable situation. A bad forecast generally means a tough setup that has the
weather folks guessing. We learn to look at forecasts with a degree of confidence
based on their past performance.
Once we have seen what the weather has done and what it is now doing, it’s
only necessary to fill in what it will be doing when we get there.
The Late Weather
There’s another point worth considering—what our airport is forecast to do after
we get there. We should know the expected weather for a period of four hours
after our arrival. This isn’t in case we’re late, although that could be important,
but rather to give a picture of the trend. If, for example, the airport is forecast
clear and unlimited for a long period after our arrival, we feel more relaxed about
the chances of its being good when we arrive. If, however, it’s forecast to begin a
gradual deterioration four hours after our arrival, then we keep an eye on the
possibility of this deterioration occurring much earlier than expected. What we are
doing is bracketing the expected weather for our arrival by getting the forecast for
before and after our arrival. What we do is slip the time of arrival, that we will
really use, in between the current weather and the future weather, seeing toward
which time, now or future, the weather is developing.
Regulations Aren’t the Important Criteria
When checking our weather data, the first things we look at are ceiling and
visibility. Are they forecast to be within VFR limits or will an instrument flight be
necessary? This question involves the FARs, which say that you need a certain
minimum ceiling and visibility to fly. These minimums are determined by
regulations, but an important point about legal minimums is that they are a batch
of words in a book and aren’t to be considered a substitute for good judgment. An
airport may be forecast to be better than VFR limits and still not be a place to fly.
Suppose it’s down in a valley surrounded by mountains that are cloud-covered;
there just wouldn’t be any way of getting in there VFR. The legal minimums may
not always be good enough for some situations.
When looking at ceiling reports, remember that the ceiling reported isn’t for
the scattered clouds, but for the broken and overcast. So if a ceiling is reported as
800 feet with scattered at 200, realize that you may have ground contact at 800
feet, but there will be annoying scud occasionally blocking your lower visibility.
If it’s raining, you can bet that the scattered will become broken or overcast and
become a 200-foot ceiling later on.
Visibility is an important factor for all pilots, whatever their experience. If
ceilings will be at or near minimums and the visibility is good, then we know it
won’t be difficult to fly, but if visibilities are low, a minimum ceiling makes flying
much tougher. If we are poking around mountainous terrain with low ceilings and
low visibilities, we are in a difficult situation. A visibility of five miles with a
1,000-foot ceiling doesn’t sound bad in Indiana, but that same weather between
Winslow and Kingman, Arizona, would be very hazardous and difficult.
The same applies to the low approach. A 200-foot ceiling with a couple of
miles’ visibility isn’t a difficult approach if turbulence and wind are reasonable,
but when the visibility drops to half a mile, the approach is much different.
Conversely, we can handle reduced visibility if there is a lot of ceiling,
allowing us to get up high enough to clear all the terrain we cannot see. In
practice, however, we prefer visibility to ceiling if we cannot have both.
Whenever we consider visibility, we should note whether or not there is
precipitation. Four miles reported by the NWS can be much less when seen
through a rain-smeared windshield. Four miles may in reality be only one bleary,
wavy mile. Airplane windshields vary in their ability to shed precipitation, and
some are really awful. If we have an aircraft equipped with windshield wipers or
any other effective system, such as pneumatics or rain repellants, this helps
tremendously. When first dealing with this issue of rain on an aircraft’s
windshield, pilots may not think there’s any problem, because they can see
through the windshield in rain. However, turn on that wiper or system, and
suddenly there is a dramatic increase in what’s visible, making us realize we had
been cheated out of a couple of miles of visibility with a rain-covered windshield.
So the airplane windshield, and how well you can see through it in rain, becomes
an added weather factor. Make this little test the next time you’re flying in rain,
straining to see ahead: look out a side window that isn’t getting rain from straight
on and see how improved the visibility becomes.
Pollution and Visibility
Visibility is also a function of smoke and haze coming from industrial areas.
Perhaps an airport is reporting reduced visibility, while the general weather
conditions are good. The reduced visibility may not be cause for alarm, because it
could be industrial air pollution drifting in from the city. A look at weather reports
from other airports in the area that are not downwind of a city will show the real
visibility trend.
In the days before a lot of industrial pollution and automobile smaze were
cleaned up, at New York’s La Guardia Airport with a light west wind, which
basically said the weather ought to be good, the visibility could be one mile, while
Newark airport, upwind from smoke-producing areas, had seven miles or more.
This still plays out in some parts of the world, at times also instigating early and
late-day haze—a possible hint to fog.
An airport’s location can mean a lot. If Long Island, New York, has a northeast
wind and there’s worry about fog and low ceilings, it’s a cinch that La Guardia
Field, on the north shore, will have worse conditions than Kennedy on the south
shore. The wind has to flow slightly down and over land to reach Kennedy, and
this will help to raise the ceiling. Conversely, a south flow in the right conditions
will clobber Kennedy, usually stopping about halfway up Queens, to the north,
with La Guardia okay. What we’re saying, again, is that we must include the
factor of terrain in our weather evaluation.
If we are going to fly instruments into an airport, we can accept a forecast that
calls for weather within legal limits for an instrument approach. However, these
limits, again, are only legal verbiage, and because it’s legal doesn’t always mean
you should go. Legal means regulations with fixed numbers like “200 feet,” but
numbers cannot cover all the factors in weather flying. Wind and turbulence can
affect an approach and may make a 300-foot ceiling seem awfully low. In an
extreme example, you might have a legal 300-foot ceiling forecast for Daytona
Beach, Florida, during a hurricane! You certainly wouldn’t want to go there. To
some degree, these elements enter into all weather judgments. If it’s going to be
necessary to descend through a thick layer of icing when a pilot’s experience and
anti-ice equipment are limited, the pilot should not be interested in making an
approach, even if it is legal. There are a lot of commonsense factors in judging
whether to fly or not, and legality shouldn’t always be the deciding one. It is folly
to think that as long as there are legal minimums, everything is okay; there’s more
to it than that! Of course, a pilot cannot operate below legal minimums unless
ready to declare an emergency or pay fines; and maybe get hurt.
There are other times when the legal minimums look too restrictive—for
example, a low stratus condition with calm air and little wind. In such a situation,
a person could probably cut a ceiling below legal minimums without much effort,
but obviously, for reasons that go beyond weather, such is not smart. Generally,
however, legal minimums are something not to go below, and there are times
when one should remain above them, times when they are too low.
Cheating on minimums isn’t clever. It’s well worth remembering that
minimums are based on many things, and the important ones are terrain and
obstructions under the descent path, to the sides of it, and in the missed approach
area based mostly on things like airplane performance, radius of turn at an
assumed speed, etc. Sneaking below minimums means we are taking the risk of
hitting something.
Speaking of not descending below minimums, of course we don’t do so unless
we see, by the time we reach minimums, the actual legal airport environment. It is
worth mentioning that aircraft with Primary Flight Displays (PFDs ) showing
artificial terrain—synthetic vision—should never tempt us to cheat on minimums,
and at the same time, we need make sure we do not get target fixation on these
displays, slipping through minimums. Once below minimums, we’re visual, with
any PFD reference only for primary flight data, which is just basic attitude,
airspeed, altitude and heading, as well as navigation indications. These displays
are amazing technology, but for whatever reasons, it is not approved, so we don’t
do it.
How Do You Feel?
Another serious factor in weather judgment—often overlooked—is how a pilot
feels. Some days we feel good and very tigerish—we’ve had a good rest, our
physical condition is tip-top, and we feel able. At other times we may be tired or
have a cold that lowers our efficiency. We may be unhappy because of anything
from a bad business situation to a fight with a spouse. It’s an honest fact that we
aren’t the same every day—athletes aren’t, and they play, fight, or compete better
on some days than others. It is difficult to stand off and objectively analyze how
we feel. But some days you’ve got it, and some you don’t, and the ones you don’t
should, under some conditions, raise your ceiling and visibility limitations.
I (RNB) can remember an all-night flight from Kansas City to New York with
stops at St. Louis, Indianapolis, Dayton, Columbus, Pittsburgh, and then Newark.
It was back in DC-3 days, and the weather was bad, with an instrument approach
at each station down through an icy overcast to minimums. The flight was a heavy
mail flight and at each station, we were delayed while they loaded and unloaded
mail. I had a new copilot, too. Finally, 5 a.m. found me in Pittsburgh looking at
Newark’s weather, which was forecast poor with precipitation. I turned to the
agent, and told him the flight would hold for six hours and quickly added that it
wasn’t that the weather was too bad, but only that I was exhausted and didn’t
think it wise to fly any more bad weather without some rest. The airline,
incidentally, never complained about it, and when I dropped by the chief pilot’s
office a few days later to tell him what I’d done, he complimented me on the
decision.
More about Wind
We’ve looked at the forecast, the ceiling, visibility, precipitation, and at how we
feel … what else ? Wind direction and velocity in relation to terrain, such as light
winds flowing from bodies of water or strong winds flowing down nearby
mountains. Some airports, snuggled beautifully against the side of a mountain,
can be a tough place to land with high surface winds. Hidden in the winds can be
the rotor from wave action downwind of the mountain, or even flow off low hills
or ridges. It may be only a few hundred feet above the ground and have very
nasty turbulence, plus areas of strong sink that will have you pouring on power
while wrestling with the rough air. The trick is to be suspicious of such things
close to mountains, or even those lower hills, and not be caught off guard.
There are details, too, of runway alignment. Now and then we may be headed
for a field with a single runway, where a crosswind will be too much to handle.
This can catch us naked even with simple VFR flying. One day, flying a Piper
Super Cub, when young and foolish, I (ROB) approached the old Evanston,
Wyoming, airport’s single runway, thrashing in a strong and gusty west wind,
only to find it dead across the runway. With the Super Cub’s short field ability,
you rarely worried about runways, but this time I should have checked before
launching over those long western distances. Thoughts of an across-runway
landing were dashed by fencing either side. Fuel was tight but okay for a return
downwind to Rock Springs, but I succumbed to destination fixation and landed. It
wasn’t pretty, all was safe, but I was not proud of the decision to land. When I
tried to leave in haste, having a commitment to be elsewhere, the airport owner
made a great statement: “Well, if you really have to leave …” I left the next
morning, the winds calm.
High wind velocity is an indication of turbulence, made even more spicy and
difficult when we are IFR on an instrument approach to low weather.
Calm winds and approaches are delightful; they are easy approaches, but
again, if we are on instruments, quite probably, because of the calm air, these
approaches will be low ones with reduced visibility.
Speaking of airports, we should check NOTAMs for the destination. Has the
snow been removed? Are the lights and facilities all working? What other things
are affecting the airport’s condition?
Altimeter Setting
Altimeter setting is reported on the weather sequences, and as we look at present
and past reports, it’s a good thought to make a mental note of the pressure and see
if it’s increasing, decreasing, or staying the same. We can catch a weather trend
this way and, keeping in mind the pressure, we have a reference for altimeter
setting in case we don’t hear one along the way. This is not recommended for IFR
flying, for which an accurate altimeter setting is needed all the time, but the
information is a little backup “just in case.”
Temperature and Dewpoint Again
On those weather sequences, we find our old friends temperature and dew-point.
We want to keep them in mind to relate to the present and forecast weather, and as
a reference when watching the trend at our destination. It’s important to note,
again, that time of day affects the value of temperature and dewpoint: sun coming
up, they tend to separate; sun going down, they get closer with chances for fog;
they come together when it starts to rain, too.
PIREPs
Pilot reports are worth careful consideration, because another pilot reporting the
height of the cloud tops, for example, is the next best thing to being there oneself.
Like almost everything else, however, these reports must be absorbed with some
thought about their validity. A report of the tops is a pretty definite thing, but
reports of turbulence can be questionable. How turbulent is it, really? One pilot,
being the nervous type, may yell severe turbulence, while old hard-nosed Joe says
it’s just choppy. Notice, also, what kind of an airplane the report came from—one
with a high wing loading, usually meaning bigger airplanes, wouldn’t be as
troubled as a lighter airplane of the two- or four-place variety. So, what do we do
if turbulence is reported? Look over the general situation and decide if there
should be turbulence; if there should, and it’s reported, that’s that. If there
shouldn’t be turbulence, and it’s reported nevertheless, then either a Nervous
Nelly was flying the reporting airplane or something has started to move in the
weather pattern that’s different from what’s forecast, and we’d better look things
over again and decide what it might be. In either case, the turbulence report didn’t
hurt and has only caused us to study things a little more and be prepared.
As pilots, we should make an effort to report the weather we find, particularly
cloud tops and bases, icing, turbulence, thunderstorms, or anything unusual. These
reports not only help pilots directly, but they help the meteorologist, which finally
comes around again to better weather information, helping pilots and a lot of other
people, too. Meteorologists have information on places that report weather, but
they do not know what’s in between. Sometimes weather will cook up something
they never knew about. A pilot has a chance to see these in-between places and
realize that something different from the report may be happening. This is the time
—an important time—to make a pilot report and to let the meteorologist know,
too. A report that says, “Snow encountered between Albuquerque and Gallup,”
may be an important clue that things are happening faster than expected, and the
meteorologist should revise the forecast.
It is important to remember that PIREPs only happen if pilots make them.
We’ll need to make those calls to the FSSs, either on their specific frequencies
in the area we are flying or on Flight Watch’s (EFAS) designated frequency—
currently 122.0, if we are flying below 18,000 feet, or on the airport’s appropriate
controlling frequency if an airport-area event. If we don’t have time to make a
PIREP in flight, say from a cockpit workload situation, and on the ground we feel
the information still timely, we can call the FSS phone number of 1-800WXBRIEF and make the report. PIREPs reporting conditions such as wind shear,
breaking action, ice on an approach are extremely important and possibly of
immediate safety benefit to other aircraft. We’ll bring this up again in related
chapters.
On the Ground, Too
Report the braking action you find on landing when ice, snow, water, or whatever
make stopping an adventure. While a larger airport may offer braking action
reports, unless they come from a friction-measuring vehicle, it is pretty subjective,
the opinion of a person tearing down the airport’s runway and then slamming on
the brakes. Pilot braking action reports are also subjective, but at least they are
from an aircraft, with the pilot understanding what is needed in the real
environment. At smaller or less-frequented airports, these reports are often the
only information available, so your braking action report is important.
Remember the opposite, too, and request past pilot braking reports for your
own information before landing on questionable winter days and nights or at times
when the runway is covered with water, perhaps the result of a thunderstorm or
prolonged heavy rain. The control tower may not always give a braking action
report. When they get busy, things can get lost in the heat of battle.
Once, while checking out a new copilot in a 727, her first jet transport
checkout, the temperatures had fallen to around freezing after recent precipitation.
A few miles out on final approach, with no braking reports from the tower, we
just had “that feeling,” so asked. The tower returned with a braking friction
number, necessitating flailing of pages in that homemade, special little binder of
important references we all should carry. The reading translated to poor, and
confirming with the tower, we were told they just give the numbers and it’s up to
us! In other words, they had no clue it was poor braking and should be advising
aircraft. We also had a slight bit of crosswind. Although skilled with many levels
of flying experience, the copilot had learned to fly in her father’s two-place, tailwheeled Globe Swift, which meant she’d had a great flying background,
including using the rudder. Her inquisitive look, towards pointers on how best to
handle it in a 727, inspired an easy response: “Just land it like you would your
Dad’s Swift in a crosswind.” She aced it.
Summing Up
For the terminal (an old term for an airport), we study forecasts for past, present,
and future; we read old and current METARs and check them against the forecasts
to see how the forecasters have been performing. We look at other terminals
within a couple of hundred miles of our destination and relate them to our
destination weather, and most importantly, we study reports and forecasts of
airports beyond our destination from which weather might come. If, for example,
we are westbound and a front is approaching the field for which we’re headed, we
check how the front has been acting as it approaches. Say we’re going from
Columbus, Ohio, to St. Louis; in addition to St. Louis, it’s important that we study
Kansas City and Springfield, Missouri; Oklahoma City; Burlington, Iowa, and a
station or two west of there, such as Omaha. A wide sweeping glance will tell us
where the action is, and then we relate it to St. Louis.
We need an alternate for our destination airport, even when flying VFR and
especially MVFR. We study alternates as thoroughly as we do the destination, and
perhaps add a few factors. One is that we want the alternate to be as good and
have as little chance of going bad as possible. While we may head for a
destination that has a nervous forecast, we want an alternate that has a solid one,
and we don’t like alternates that do not have a solid forecast.
In tune with this, we should always have, tucked back in our mind, which
direction to go for an “out”—a diversion toward improving weather, the safest
weather area. This is important for all flying, but especially VFR.
Legal alternate minimums are fairly low, and it is possible to have an alternate
that is forecast to be above alternate limits for arrival and below them an hour
later. This brings about such statements from pilots as, “That’s the paper alternate,
but my real out is ____.” They want something that’s definitely going to be good,
like an airport that is behind a front and on the uptrend or one that will not be
influenced by the destination weather, like Montreal when the New York area has
a low moving off the coast. Long Beach, California, may be a legitimate alternate
for Los Angeles, but a knowing pilot says that Palmdale is the solid-gold out when
those low clouds from the sea start to roll in, or Newark is no good for JFK, as
one thunderstorm can kill the whole New York area. It’s wise to consider that the
FARs give numbers to go by, but because weather isn’t a precise, number-specific
phenomenon, one often needs extra protection above and beyond the FARs.
Paradoxically, or hypocritically, the FARs are often too restrictive and hold us
back when it isn’t necessary. However, this is the outcome of interplay between
the need for definite rules in the book, and the fact that so much of flying and
weather depends on judgment. Judgment is difficult to cover in regulations. I’m
glad I don’t have to write them.
It’s worth noting, before we leave the thought of terminal, or airport, weather
and the ways of looking it over, that we always relate our weather study back to
the basics: big picture, time of day and season, temperature change, moisture
change, terrain, wind, forecast, and the almighty “IF.”
7
Checking Weather for the Route
After considering the destination and deciding it’s good enough, we have to learn
what’s in between: the en route weather. What bothers us en route? If we’re VFR,
it’s cut and dried: we must have enough ceiling and visibility to stay VFR, and the
more mountainous the terrain, the more ceiling and visibility we need. We can fly
on top of clouds, but they really should be no more than scattered and very clearly
and confidently forecast to stay that way!
On instruments, our concerns are ice and thunderstorms, cloud tops, bases, and
ceiling underneath, especially if we’re single-engine and want some degree of
tranquility regarding the possibility of engine failure. Turbulence is a factor, but is
generally related to thunderstorms or mountain issues. Wondering about ice and
thunderstorms, the important question is: Are we dealing with them in fronts or
only air-mass conditions? This knowledge is very important, because with airmass thunderstorms, your chances of steering around them are good; for ice, you
probably can get on top, unless the tops are too high over mountains. Through
fronts, however, the thunderstorms will appear as a solid line that’s impenetrable,
and ice will be between you and the other side of the front, with strong
probabilities of confrontation.
VFR or IFR, of course, we want to know about winds—head or tail and how
strong. More of all this as we go along.
The big picture has its usual importance, and we want to take note of the
weather system that may move onto or off the route. The method of looking over
en route weather is much the same as for the terminals: we want the same scrutiny
of forecasts for before, now, when we get there, and after. We mix in the same
factors and emphasize terrain, because it intensifies any bad weather that may lie
along the flight path.
Weather Is Mostly Good
We talk a lot about bad weather and may put a gloomy look on everything, but
we’d like to make two points. One is that if we only talked about clear weather,
there wouldn’t be much to talk about. The other is that most of the time, thank
heaven, the weather is good. We fly in clear skies more than we do in annoying
cloudy ones. We may have cloud cover due to postfrontal conditions, but it is easy
to top and fly above.
Fronts along the route, with their associated low-pressure areas, are the things
that can make it tough. In these areas, we find the difficult weather, the ice or
thunderstorms, thick cloud decks, precipitation, high-speed winds, and turbulence.
But this kind of weather covers our routes only a small percentage of the time.
I (RNB) spent four and a half years in weather research, trying to find bad
weather. I sat on the ground many, many more hours waiting for bad weather than
I have ever sat as a pilot waiting for good weather. Often, too, the bad weather
that was supposed to be out there wasn’t, and instead of ice or snow, I’d find
myself flying disappointingly on top, looking at blue sky or stars. All this is
simply to say that things are good more than they are bad, but we have to talk
most about the bad.
Clouds rarely start at 200 feet and go up in a solid mass to 30,000 feet or so.
We can draw a mental vertical section of how clouds are stacked. They are usually
in layers that become more complicated, and the spaces between them fewer, the
closer we get to a low or front. In their simplest form, we may have a single
stratus deck behind a cold front, one layer with a reasonably reachable top, or one
layer where warm air is overrunning cold ahead of a warm front—a cirrostratus
deck, for example—with a high base and nothing below. Then, closer to the warm
front, we find an altostratus layer with a lower base. Closer in still, this lowers
further and rain starts, whereupon a low stratus deck forms, adding another layer.
At the front, the layers merge.
Something on Fronts
A cold front has much the same profile, but its area is smaller. The distance from
front to back is shorter, and it does not take long to fly through the front. A cold
front can, however, be more violent than a warm front. Warm fronts are slow—
and sometimes tormenting—while a cold front is a quick punch in the nose.
As we know from primary meteorological study and from picture-book
drawings, fronts come out of a low-pressure system. The warm front is a long arm
sloping out ahead of the low, and the cold front is another arm pointed down,
southward, from the low. The farther away from the low we are located on a front,
the less violent the weather, and the closer we are to the low, the tougher the
weather.
Occlusions and Zippers
A type of front we haven’t talked about is the occluded front. I (RNB) remember
when I was a very youthful copilot who hung around the weather office on my
days off, and I asked the meteorologist what an occlusion was. He said, simply,
“It’s just like closing a zipper.” This really didn’t tell me much, until I learned
more and found that his explanation was quite exact. At the center of a low, the
warm and cold fronts meet. When, near the center, they get together and one
catches up with the other, they form one front. This process of catching up
progresses downward from the low center. It’s as though a zipper pull handle were
at the low center, with one side of the open zipper the cold front and the other the
warm front; the zipper closes—pulls—southward as the cold and warm fronts
come together and become an occluded front. What does it all mean? Generally, it
means the low is beginning to fill up and weaken, with cloud bases getting higher
and tops lower, until the low is finally a trough with little weather. But in the early
stages of an occlusion, things can be rough and tough, with the characteristics of a
cold or warm front, depending on whether the cold air is catching up to the warm
front and lifting it upward as a cold front or riding up the warmer air ahead to give
it the qualities of a warm front.
Sometimes the “closed zipper” portion of the occluded front tips and bends
over backward. It is then called a “bent-back occlusion” and will act like an
additional cold front. Because of the counterclockwise circulation about the low,
such an occlusion is fed moisture and can cause some mighty mean weather. With
the low near a coastline, a massive amount of moisture is fed back over the top of
the low behind the occlusion. The low may move slowly, or not at all, and just sit
there spinning around, moving that moisture back around it. Such a low, stalled
over the Gulf of Maine off the New England coast, can bring massive snowfalls
and foul weather for days.
Generally, we think of an occlusion as “occluding out,” which means that the
low is starting to fill and die. Like everything in weather, however, you cannot
always count on this, and while an occluding low generally spells gradual
improvement, it can, on occasion, regenerate itself and create more bad weather.
It’s necessary to keep a close eye on occlusions. Visualize from where an
occlusion may continue to have a moisture source to feed into it as a hint to what
may happen. If it’s in the dry part of the country, and a big moisture source is not
available, then the low will fill and things will get better. But near an ocean or
gulf, watch out!
Large-Area Weather
Some frontal conditions can be very widespread, causing weather to cover a large
area. We find this most often in winter, in big lows having large areas of
overrunning warm air in their northeast sector. In winter, these can cause large
areas of freezing rain. Usually this type of storm is not difficult to spot or predict,
and the Weather Service will have it sufficiently well analyzed to make an
accurate forecast, but that doesn’t relieve our task of keeping a skeptical eye on it.
As far as flying into such an area is concerned, we shouldn’t; it’s better to
consider the coziness of a fireplace and a good book, unless we’re experienced,
well equipped, and have lots of fuel.
The Important Northeast Corner
As we study weather systems, it’s important to visualize where the weather is. In a
low, most of it is ahead of the system, in the northeast corner (in the northern
hemisphere). This is ahead of and in the warm front. If we were to cross a system
starting in the east-northeast and fly southwest, we’d first fly under high clouds,
then into an area of rain or snow or possibly freezing rain, and then through an
area of heavy precipitation, ice, and thunderstorms. This is the warm frontal
surface. Then we would break out in a relatively clear area with a deck of
cumulus or stratus or even clear skies. This is the warm sector. Incidentally, a low
will generally move in the direction in which the isobars are oriented in the warm
sector.
Past the warm sector, we’d bump into the cold front: a narrow band of
thunderstorms or ice, with lots of clouds and turbulence, but a fairly quick
passage. Immediately behind a strong cold front there is a clear area, and we may
think all is over, but as the cold air builds in, a stratocumulus deck will develop,
and in winter probably will become a solid overcast with fairly high tops and lots
of ice in the clouds. But as we fly farther from the front, this cloud mass begins to
show breaks, then becomes broken and gradually scattered, with the tops
lowering, and finally there will be clear skies. How fast all this occurs depends on
our distance from the low’s center.
The interesting part of the system, however, is that northeast portion. In this
area are the easterly surface winds that cause fog and low clouds. Toward the
front, precipitation begins, causing low clouds, and wide areas of poor visibility
and ceiling. In winter, rain aloft will fall into cold air and create freezing rain and
ice storms. This is also the area of heavy snowfall. This area may often be
extensive enough to make finding an alternate airport difficult; it can also take a
long time to move off. Although we cannot forget the cold front, the big action is
up there ahead of the warm front, and this can be true hundreds of miles away
from the low, as well as near it.
In Dr. Horace R. Byer’s book, Synoptic and Aeronautical Meteorology , he
says, very accurately, “The warm front situation may properly be regarded as the
most serious hazard to aviation …”
A weather system—the big picture. Note all the clouds and problems in the
northeast sector. Thinking of this picture and then relating it to your location in
an actual weather situation can tell you what weather to expect and which way to
go. It’s a picture that deserves a lot of study and mulling over. (Note the jet stream,
which would be up high, near the tropopause.) (NOAA PHOTO)
That’s a good statement, because a warm front has it all, and it’s not simply
the frontal surface itself, but also the big area northeast of it that requires study
and respect when we look over the weather.
While studying the warm front and the NE sector, it’s a good idea to visualize
being in various parts of this and which way we’d retreat toward better weather.
The warm sector, south of the warm front, generally has the better weather,
though we should watch that area for the eventual arrival of a cold front from the
west. Running away toward the NE demands care to be certain the weather isn’t
running with us and preventing our escape from the lowering ceilings, visibilities,
thunderstorms, and increasing precipitation.
Warm fronts slope, in a shallow way, from 100 to 300 to 1. So, if the frontal
surface—the place where surface reports show wind shifting from easterly to
southerly—is at, say, Amarillo, Texas, a pilot will find the warm front aloft
anywhere from 100 to 300 miles northeast of Amarillo. That would be the altitude
where warm front thunderstorms begin, or how high we’d have to climb for
above-freezing temperatures when there’s freezing rain down low and we want out
of it. This warm front slope is worth mulling over at leisure and important to note
when checking weather.
Drawing of a low taken from an actual weather map. Note the mass of clouds on
the northeast and north side, extending far west. Also note the east wind covering
that entire area, bringing in the messy weather. Be wind conscious; where it
comes from and what that source region is like and what weather it may breed.
Go the Short Way
From studying weather, we tend to get the idea that we are always flying through
fronts at right angles. Of course this isn’t the case; sometimes our course is along
a front, or at any angle to it, in which case tough weather can be prolonged. So
there are times when it’s wise to detour a bit and take on a front at right angles
rather than slugging it out for a long period along the front.
The analysis of weather in lows and fronts tells what we may have to contend
with en route; this is what we are looking for when we study the big picture.
Checking the en route weather, the VFR pilot decides if the ceilings and
visibilities are high enough to fly safely under clouds. If the decision says they
are, then the question is, will they stay that way? The pilot wants to know if any
system is moving in that will make the en route weather deteriorate. If there is
approaching weather, but the pilot thinks there is time to complete the flight
before it reduces the ceilings and visibilities below a workable limit, then the pilot
must decide which way to run and what to do if the deterioration occurs ahead of
schedule, with visibilities going down and the ceiling forcing the airplane lower
and lower.
We must remember, and it’s very important, that the timing of forecasts is not
always exact; they cannot hit precisely the moment when a front will pass, or a
place fog in or clear, or any other weather will occur. The state of the art is not
such that weather can be forecast all the time with absolute accuracy. That’s why
we must know weather and watch its movements all the time. We may repeat this
theme many times, because it is so important. We may be puzzled by weather’s
changes, but we should never be surprised or caught off balance!
The instrument pilot looks at the weather en route differently. She or he can
accept weather that has ceilings and visibilities well below those necessary for
safe contact flying. The question is, how tough will any turbulence, ice, or
thunderstorms be in relation to the equipment and pilot ability?
It Takes Time to Know
It would be easy to say that if pilots are going to fly instruments, they should
know how to fly instruments extremely well and should have all the equipment;
but this isn’t very realistic. Even an FAA-rated instrument pilot has to go through
a learning period. The rating, though earned after a lot of hard work, is only a
beginning.
The FAA says, in effect, that rated pilots, new or old hand, may take off, go
immediately on instruments, stay on instruments, fight ice and thunderstorms,
shoot a 200-foot ceiling in heavy rain at the other end, miss the approach, pull up
on instruments, and go to an alternate and make an approach there. That’s a pretty
exciting day’s work for the newly rated pilot, especially flying without a copilot,
maybe no autopilot, while also busy getting ATC clearances and tuning radios, or
the busy workload of constant function for electronic instrumentation.
It’s obvious that the less experienced pilot doesn’t want to fight all that
(sometimes the experienced one doesn’t either); so what does the new pilot do?
Learn to crawl, then walk, and finally run; that is, take on weather a little bit at a
time, gaining experience with each flight. This comes up again in the chapters
discussing instrumentation and flying proficiency.
Seeing a weather map is an important part of studying en route weather, but at
times, a map isn’t available. Then we must get all our information from forecasts.
Either way, maps or not, a lot of the weather comes from TAFs, METARs, and
other products, so we must learn to read, hear and put together a picture from that
time-proven coded data.
If we get our weather from the FSS we see example of a proper, systematic
briefing, which is what we should replicate if we get the briefing ourselves from
computers or personal electronic devices. First, their briefing starts with a
synopsis, which demonstrates that the Weather Service and FSS also like to begin
as we do—looking at the big picture. Then they go on to tell cloud bases and tops,
where icing, thunderstorms, and turbulence will be, and what the outlook is for the
next weather period.
The forecasts come next, and we listen to them carefully, trying to visualize
where all this weather that’s going on. We try to make a dull bunch of words and
symbols come alive and paint a picture. It may say “–22020G30KTS 3/4SM SN
VV012, TEMPO 1/2SM SW OVC003,” which doesn’t seem to make much of a
picture; but it can if we concentrate.
The ceiling is going to be indefinite, 1,200 feet, which isn’t bad; but threequarters of a mile visibility gives a gloomy sight of flying in severely reduced
visibility. We’ll see only straight down and very little ahead, especially in snow.
The ground will be snow-covered and all look much the same; navigation will be
difficult. If the terrain is hilly with mountains nearby, we’ll have to be extra
careful. It’s not a VFR operation.
The report continues to say that the ceiling occasionally (temporarily) will be
300 feet, ½-mile visibility in snow showers. We picture sudden deterioration in
conditions, as the wind picks up and heavier snow showers come in gusts. Your
skeptical nature tells you that the visibility will not be ½ mile from the cockpit,
but more like ¼ mile. We know it will require an instrument approach to the
runway, but possibly those snow showers will take it below minimums.
Probably one of the most important points in these TAF forecasts is the
probability outlook stated, for example, as PROB40 0407—which means there’s a
40 percent probability between 04 hours and 07 hours that something will be
better or worse, the “something” being indicated by the coded letters for the
weather condition. The TAF might also say, “BECMG 0407 _” [Becoming
between 04:00 and 07:00]. What it will become will be expressed in the code; FG
for FOG, SKC for SKY CLEAR, and so forth. What the coded expression
PROB40 really tells us is that there is some question as to the preciseness of the
forecast, that there’s some doubt, which is a signal for us to be extra wary and to
watch and keep up with the weather’s action.
The statement “BECMG 0407” means that between 04:00 and 07:00, things
will change for better or worse. It’s our job to see how that prognostication is
playing out; if it’s supposed to become better in that time period, it’s our task to
watch and see that it does, which means the old business of getting the en route
weather reports each hour and writing them down in order to compare the latest
with earlier ones to learn which way things are going. If we are fortunate to have
airborne data link weather, it’s easy to call up these needed reports, but if not,
don’t be bashful about asking by radio for the latest forecast or any supplemental
ones that may have been issued.
Important in our en route flight are the winds aloft. First, of course, we study
them to find their direction and velocity for flight-planning purposes, so that we
know how long the flight will take and how much fuel we’ll need. Add 20 percent
to headwind velocities and take away 20 percent from tailwinds as a “fudge
factor.” That’s about as accurately as they are forecast on an average.
The winds should be studied at various altitudes. We are generally accustomed
to the idea that the winds are stronger the higher we go, but this is not always the
case; sometimes we find lower velocities up higher, which could help if we are
flying into a headwind. We study the wind at various levels in order to choose the
best altitude at which to fly. An old rule used in DC-3 days when flying into
headwinds was to fly high in southwest winds and low in northwest to reduce the
wind effect. It’s not always true, but it’s not far off. Although the DC-3 is past, the
weather at those altitudes isn’t, and that’s where a lot of general aviation still flies,
often at similar speeds.
Wind is really a secondary factor in selecting altitudes; weather is first. We
wouldn’t want to fly in a deck of icing clouds merely in order to have a better
tailwind or less headwind. So weather is really the first factor in picking an
altitude (besides terrain clearance, of course, which comes before everything), and
wind is second. Airplane performance is another factor. We want to cruise as close
to the airplane’s optimum cruise altitude as possible; weather and wind will
dictate whether we can or not.
It’s good to keep in mind the wind at other levels, in case ATC sends you to a
different altitude than the one you want. The trip might take longer at a different
level. How will this affect fuel reserves? In a jet, this could be quite serious, but
it’s also important in a 100-horsepower light plane.
The winds aloft also give weather clues. Suppose the wind for the trip was
forecast southwest, but as you fly, you find the wind really coming from the
southeast. That’s a clue that the weather may be starting to do something different
than what was forecast, and it’s time, again, to watch developments more
carefully. Especially in the eastern half of the United States, pay special attention
when the wind works toward east for generally deteriorating weather changes.
Another wag is that if we’re in post–cold frontal conditions and the winds are
forecast west to northwest winds, but they swing southwest, a little post-frontal
trough may be brewing, maybe kicking up a line of showers.
A last important point about studying en route weather regards deviating
around weather. We should not look only at the weather on the direct line between
where we are and where we want to go. The old idea that the shortest distance
between two points is a straight line doesn’t always apply in flying. We should
look well to either side of our route and see what’s going on. Sometimes we can
circumnavigate bad weather. Sometimes making an end run is worth it just to get
better winds, because we are not interested in how far we fly in an airplane, but
how long it takes. Going “off course” to get better winds may actually make the
flight shorter.
This is especially true for long flights. If we’re flying from the Midwest to
California in winter, it’s generally better to go via El Paso than via Denver; the
mountains are lower, the weather less violent.
Even short flights sometimes can be flown in better weather by a small course
deviation. As we said before, it pays, in studying en route weather, not only to
look on course, but on both sides, too. This applies particularly when there are
thunderstorms rumbling about.
The radar summary maps show the basic areas of thunderstorms, while
NEXRAD, both on the ground and in the air, gives us tight data of these areas—a
real heads-up. We can often go around the entire mess, which usually means less
distance and time compared with coming up to weather then having to make a big
cut around it; sometimes this latter path is too close and too intense for slower
aircraft to escape without being engulfed by the weather! However, we again
repeat that the radar maps and NEXRAD are not for use to wiggle through a
thunderstorm area; that’s a job for airborne weather radar.
Why and If
Forecasts and synopses aren’t enough; we need to know what the weather people
are thinking deep down inside behind the official stuff that comes from the
computer.
We should talk to a meteorologist if the weather setup is dicey, which was why
we used to go to, or at least call, an NWS station where real meteorologists live
or, if you are subscribing to it, one of the special weather service companies that
have meteorological staff. Again, there are NWS offices that will accommodate
questions; they just are somewhat challenging to find. The reason we want to get
this analysis is to know what the forecaster’s confidence really is. What is the
chance of the forecast working out as advertised? Is the forecaster 100 percent
sure? Fifty percent? It’s important for us to know. Getting a clue to their thinking
not only tells us how cautious to be, but it also gives us a chance to ask “why”
questions. If the ceiling is going lower, “why” is it? If the answer is because of an
approaching front, then “why” is it approaching? That might result in us being
told about a low-pressure system on the move, and then we ask “why” is it
moving this way, how fast? The answer might be that a high-pressure area is
blocking it from moving in another direction. And we could ask “why” is the high
blocking and not moving? If we ask enough “whys,” we can finally get a feel for
how solid the facts are on which the forecast is based and thus how much
confidence we want to put in it.
Asking “why” is a wonderful way to do this, and a great way to learn more
about meteorology, too. Unfortunately, we usually don’t have a meteorologist to
talk with and have to rely on the published forecast percentages we spoke of
before. If there isn’t any way to ask the “why” questions, we can ask them of
ourselves and try to figure out the answers as a good way of evaluating what may
or may not occur. This, of course, really outlines the task—both knowledge and
ability—for those seeking weather electronically, all by themselves.
After “why” comes “if.” As we absorb the forecasts, the big picture should
form a background in our mind into which we fit the forecast, and while doing
this, we develop our “if” thoughts.
“If” thinking is very important, as we say to ourselves what “if” the front
slows down, what “if” it speeds up, what “if” the wind stays east, what will it be
like and what’s the effect on me “if” the forecast does a 180-degree flip? And we
ask ourselves, “if” it does something unexpected, what will I do in flight? Being
“if” conscious keeps surprises out of our lives and has us prepared for something
worse that might come along.
A simple example is a cold front in eastern Ohio. We might be flying from
Bridgeport, Connecticut, to Harrisburg, Pennsylvania. The forecast says
Harrisburg will have scattered clouds, visibility five miles in haze, and southwest
wind. It will stay that way until 17:00, when the scattered will become broken
with a risk of thunderstorms. The forecast for later shows thunderstorms and a
frontal passage.
It’s no problem for us, because we are going to arrive there by 14:00, long
before the thunderstorms. But our “if-mind” says, “Keep an eye on it.” The front
is out there and moving; a prefrontal line squall could pop out ahead of the front.
We would do well to get the latest weather before leaving Bridgeport and current
weather as we fly en route.
All this example does is demonstrate the kind of thinking a weather-wise pilot
does, especially in relation to that synoptic picture.
In this simple case, it’s obvious the forecaster based the terminal estimate on
the movement of the cold front. It looks as though it will move, but will it move at
the rate expected? Best information says it will, but as we know, they cannot hit
frontal movement on the nose. The forecaster planned for that a little in the report
when warning of a risk of thunderstorms for 17:00 in case things moved faster
than expected.
In the same weather conditions as above, if we were coming from Dayton,
Ohio, to Pittsburgh, we might be expecting Pittsburgh to be in good weather
behind the front, but if the front slowed down, Pittsburgh would not clear out, and
the front could still be in the area for our arrival. It’s all part of the necessary
suspicion, the constant knowledge that weather forecasts do go sour.
So when we look at the weather, we keep in mind several key points: big
picture, time of day and season, temperature-change possibilities, moisturechange possibilities, terrain, wind, forecasts, and the big what if!
Don’t Fear Weather …
All the emphasis we’ve put on weather so far may make it sound as though the
sky, most of the time, is full of fearsome conditions. Well this isn’t so, and even
when bad weather prevails, respect, not fear, should be the attitude.
Weather makes flying interesting, even though it frustrates us at times. But if
we fear it, our flying will be affected; we will not perform as well as we can, and
emotions may overcome judgment. It is fun, more often than not, to fly in bad
weather. It makes us feel a part of nature again and not a coddled creature living
only in soft comforts; it builds our confidence. The point is that to handle weather
we must know, again and again, that it is capricious and its movements unreliable.
What we are trying to do is make certain that we outguess this uncertainty and
when we cannot do that, be prepared to handle it. If we prepare by obtaining
weather information before flight, keep up with it in flight, and have alternate
action always available, then we have respected weather and can handle it. But if
we do not do these things, we may well find ourselves in an alarming position,
scared of everything around us and not thinking clearly—a recipe for disaster!
… Or Worry about It
Worrying about weather shouldn’t upset our lives, and it doesn’t help to fuss in
advance over what it’s going to be like when we fly. In my youth, I fretted about
weather days ahead of a cross-country flight: Would there be ice? Thunderstorms?
Low ceilings? Using a little extra imagination, it was easy to get all upset.
But somewhere along the way, I realized that there wasn’t any way I could
confront that weather until the day came to fly it, so there wasn’t any point in
stewing about it in advance.
It’s good practice, of course, to check weather daily, in moderate fashion, to
keep the trend—the rhythm—in hand, but the time to get steely-eyed serious is
when first walking into the briefing office (sadly rare these days), sitting down
with a computer or personal electronic device focused on a good, thorough
briefing, or picking up the telephone to obtain the information. Then, with a good
briefing and thoughtful preparation as to fuel, alternates, and how to approach
what is out there, we can deal with the conditions in a relaxed and unworried
mood. But worry the night before? Never! That’s the time to get some sleep and
be ready for what comes on the morrow.
8
Equipment Needs for Weather Flying
It is almost impossible to talk about flying weather without discussing the
equipment of both the airplane and pilot. The airplane we fly must fulfill certain
requirements, not only of instruments and radio, but also of power and range to
battle the elements when necessary. This doesn’t mean it has to be a big fourengine transport, or even a small two-engine one, but the airplane should have a
decent rate of climb, and more importantly, it must have enough range for the
flight, from takeoff to destination, against a strong headwind and along the
wiggling course that may be necessary because of ATC. There is an impressive
difference between the straight-line distance between two places and the distance
measured over the wandering routes of the Federal Airways System.
It’s Farther Than You Think
While the shortest distance between two points is a straight line, airplanes, flying
IFR routes over the airways, don’t always fly that way. One route we often flew
was a 251-mile direct flight from Van Sant airport, a small field in eastern
Pennsylvania, to Montpelier, Vermont. If we filed instruments, however, the
airways distance was 304 miles, more than 50 extra miles, and in a 172 Skyhawk
that’s a lot.
Another flight made around the New York area was 60 percent longer by an
ATC-cleared route, which avoided the New York airport area, than over a directly
filed route. These extra distances take lots of additional fuel and that affects
safety. Suppose we were trying to beat darkness and approaching weather—a
slightly stupid combination—and then found our ATC clearance was via a
modified route that would take 70 minutes longer, not counting possible
headwinds. We could easily run low on fuel, fly into darkness, and meet bad
weather head on. To plan ahead for this possibility, we can check the many
preferred routings—“canned routes” developed by the FAA/ATC folks—not only
between defined city pairs but we can also link into these routes from smaller
airports near the main pairing ones. We can find data on these routes before
departing, either online, from ATC, or by contacting an FSS, as well as
publications such as the Airport/Facility Directory.
In considering our aircraft’s range, we should also include enough fuel for
reasonable holding at the destination and then diversion to an alternate airport
against a headwind. Although this holding fuel is not required for noncommercial
aviation, it is a good idea, considering the myriad of surprises we can encounter,
from weather to an aircraft with a blown tire blocking a single runway.
Furthermore, of course, some fuel should remain in the tanks when arriving over
the alternate, legally enough for 45 minutes at cruise speed, but more is not a sin.
In summary, this is the needed range:
1.
2.
3.
4.
Departure to destination, (considering wind and weather), plus
Holding fuel, plus
Fuel to alternate (again, winds, weather, and normal cruise speeds), plus
Reserve over the alternate
Let’s break these down further.
Departure to Destination: Departure to destination, the long way. It is most
important to know the en route time, with winds, weather, and normal cruise
speed taken into consideration. If we are going through bad weather, the wind
may be strong, and we may need to deviate around challenging weather
situations. Slugging against the winds of an active low-pressure area may give
ground speeds low enough to cause apprehension.
We need fuel for departure and arrival wanderings as directed by ATC. You do
not simply fly to the destination’s approach point, make an instrument
approach, and land. If it’s a busy terminal you may be told to fly vectors that
add many miles to the distance already flown over the wandering airways. One
route into JFK from the north has an average vector distance of 91 miles! If
we’re flying a jet, and doing it at a low altitude to which we may have been
cleared, those 91 miles can use up a lot of fuel and make our reserve a
considerably nervous, lower amount than we’d like to have. Sometimes, in the
vicinity of coastal or lakeside cities, these vectors can also carry us over big
areas of water—something to consider in a single engine aircraft. (This makes
life vests as regular equipment a worthy thought; they don’t take up much room
and weigh little.)
During climb, fuel consumption is higher and speed lower, so the altitude to be
flown will affect the total fuel needed. This can be determined with knowledge
of the average rate of climb, the average true airspeed during climb, and the
fuel consumption at climb power. Today, new aircraft manuals provide more
complete performance information, such as better climb data, but many of us
still fly older equipment. As a ready reference in flight planning, a pilot can
make a handy, small chart that will give the fuel burned and the miles made
good by the airplane in climbing to various altitudes, as well as for cruise and
descent. The one we made is in two places: one in our flight kit for flight
planning and the other stuck on the side of our airplane’s headliner, in the
pilot’s view, along with the checklist.
Weather uses fuel. For example, in icing conditions, the airplane can lose speed,
and because of extra power and/or carburetor heat, the fuel consumption will go
up. Wandering around thunderstorms also adds miles and consumes additional
fuel. It is difficult to say with precision how much to add for ice or detours
around thunderstorms, and pilot judgment must prevail. But awareness of the
fact that these things take fuel is a good beginning, and a 10 percent cushion
will serve as a start.
Holding Fuel: Again, it is difficult to judge how much we need, but there are
factors to help us make an educated guess. First, is our destination a busy
terminal? If so, the delays can be long. Obviously, if we are going to Chicago’s
O’Hare, the delay will be longer than for Reading, Pennsylvania.
Time of arrival may also affect holding time. Any big terminal will have much
longer delays during their busy times; say, early morning, a midday push, or
between 4 and 8 p.m., rather than at midnight.
Holding ability also depends on the airplane. A piston-engine airplane’s fuel
consumption can be quite miserly when just lolling about at low altitude. A jet,
however, uses lots of fuel, and is especially critical at low altitudes. If jets can
hold above 20,000 feet, their fuel consumption can be brought within
reasonable limits. However, the modern higher-bypass jet engines are less
greedy than straight jets, especially at low altitude, but still not like a piston
engine or some turboprops.
The weather forecast enters into the holding problem. A person doesn’t want to
hold, for example, while waiting for the arrival of a cold front. If ATC says the
hold will be for an hour, with a cold front due within that hour, and reports
indicate that the forecast is accurate, it may be wise to proceed immediately to
the alternate and forget about holding. If it is late and fog has formed, there is
no point whatever in sticking around. This, again, emphasizes the importance of
keeping up with a range of weather reports in flight.
As a yardstick for the minimum holding fuel, there should be enough for 1½
hours at a busy terminal and 30 minutes at more out-of-the-way places. Traffic
can back up badly at a busy terminal or alternate because of thunderstorms, or
even just wind changes necessitating “turning the airport around,” as the saying
goes when changing runways, during which landings may cease entirely.
Traffic keeps pouring into the area, and stacks up even worse than in winter
conditions. We’ve seen busy airports go from 15-minute delays to those
approaching two-hours in a matter of minutes, because a thunderstorm hit the
field: it had number one priority!
Fuel to Alternate: Fuel to alternate is just like fuel to destination and should
include the same factors, that is, total “long” distance routing, wind, and
weather en route. As mentioned elsewhere, watch out for alternates too near the
destination, potentially messed up with the same weather problems.
Fuel consumption can be computed on a long-range-cruise basis to save fuel,
but that’s shaving hairs unless we absolutely need to, so if possible, we should
use normal cruise. Concerning long-range-cruise, it’s surprising how it will
save fuel, especially with larger aircraft, even into a fairly strong headwind, but
it may not save much at all in very strong headwinds. A little study using a
computer and an airplane manual—at a leisure time—will show this.
Speaking of headwinds, they affect airplanes according to their true airspeeds.
A 50-knot headwind against the no longer operational, but magnificent,
supersonic Concorde was about 3 percent, or something like six minutes extra
time on a Paris–New York flight of 3,200 nautical miles. But 50 knots on the
nose of a Cessna 172 is 45 percent, which means an hour and nine minutes
extra between New York and Washington, about 175 nautical miles.
It’s important to explore headwind and tailwind numbers in order to know what
they do to range and fuel, on our individual airplanes, at normal and long-range
airspeeds at different altitudes. With this knowledge, we can quickly set up for
maximum range when we really need it.
Reserve over the Alternate: Reserve over the alternate depends on the
weather at the alternate. If it’s clear and forecast to stay that way, the reserve
can be minimal. If the alternate isn’t clear and instrument approaches are
required, even with a fairly high ceiling of 1,500 feet or so, more fuel is
needed, because there may also be traffic delays at the alternate. Often, when an
airport closes down or becomes unusable, everyone holding at that airport flies
off to the same alternate. This moves the congestion from one airport to
another, and the alternate can be a madhouse of delay and confusion. Arriving
over the alternate with minimum fuel in this situation is a scary proposition.
Sometimes weather stays bad far beyond when it was forecast to improve. This
can require creative changes to the whole game plan, which can work well and
timely if we are checking weather along our flight’s route, far in advance of
intended arrival time.
One morning, I (ROB) was heading for Seattle and early fog hung around
three hours later than forecast, producing below minimums visibility. Although I
was flying a 727, the scenario could apply to any aircraft, general aviation or
otherwise. The forecast had allowed one of those “paper” alternates of Boeing
field, literally down the road, it too still fogged in, as it was from below Portland,
Oregon, to Canada. Holding started east of the Cascade Mountains, which was
good, as we were not thrilled with the idea of holding over the coast, then, if
nothing improved, having to make a fuel-sucking climb back over the mountains.
Pasco, Washington, was a safe alternate and lay below in clear skies. Finally ATC
said things had lifted to minimums and an aircraft with similar minimums to ours,
(which was important, as some aircraft with Category III ability had been making
approaches and landings), would try the approach. We cautiously headed west in
kind of a straight line hold, slow and up high saving fuel. That airplane missed the
approach, so realizing it would become an iffy situation, with more holding and
plenty of aircraft ahead of us, we turned around and dove into Pasco, quickly
fueled, then reappeared in Seattle about an hour and change later. Had the aircraft
ahead of us made it in or diverted? You know, we really didn’t care, because our
decision was safe, with good cushion.
Generally, when one decides on making a diversion to an alternate, it’s often
best to stick to that decision, even if tempted by suddenly improving weather at
the original destination. Unless we have gobs of fuel, or the clearing weather is
dramatic and bulletproof, we can easily find ourselves stuck in the middle, with
no airport reachable; one due to bad weather, the other from lack of fuel to reach
it. Sometimes it’s hard, with ATC telling us the weather has just improved and we
can probably make it in, but we may find it best to forget that original destination
even exists.
As we begin weather flying, of course, we should pick alternates that are clear
and definitely forecast to stay that way. When we say “clear,” we mean broken
clouds or better and ceiling 2,000 feet above the highest terrain within 50 miles.
With experience, as well as thinking far ahead during our flying, we’ll begin
picking up on things that will have us making good decisions way before it’s time
to do so. It is most important to develop a personal disconnect from pressured
temptations, that might have us pushing limits when presented with delays,
diversions, and even cancellations.
Fuel and the Law
Alternate fuel reserve should be 45 minutes—the Federal Aviation Regulations
say at normal cruise power setting—but it’s good to keep in mind that this is the
final fuel and when the last of it slides through the engine, all problems become
simple. You are going to land, right now, wherever you are!
The government regulations spell out fuel reserves, but these certainly should
be considered minimums. This is all they ever could be, because it’s impossible to
write regulations that cover all conditions—especially considering the fickleness
of weather. Having sufficient fuel is one of the greatest safety factors we can give
ourselves. It assures the mental tranquility that is of paramount importance in
weather flying. A pilot running low on fuel may make a hurried emotional
decision that is wrong.
It’s worth reflecting that fuel management is a major cause of engine failure.
Good management means, for one thing, having enough fuel—not running out! It
also means having the good sense to be certain the fuel valve is always on a tank
with fuel in it. Airplanes have run out of fuel and made forced landings with the
fuel valve on an empty tank, while fuel remained in another tank!
The added advantage of being able to accept a wandering route from ATC,
without being unnecessarily concerned about fuel, makes weather flying an
interesting, enjoyable experience, rather than a nervous and jittery ordeal. The
ability to fly out of the weather area and go where it’s clear is a solid comfort of
the first order. A pilot should never be in a position where all the bridges are
burned and there is no way out. A fat fuel reserve goes a long way toward
providing the necessary out. Desperation due to a dwindling fuel supply has
undoubtedly caused more weather accidents, by far, than engine failure.
Fuel Again
There are two ways to deal with fuel. One is to have lots of it. Most new airplanes
are better in this regard, with some older designs also quite good. However, those
lacking are usually designs with less performance, including lower cruise speeds,
so we’re back to headwinds taking a bigger cut out of their capability. This issue
is also magnified when flying lonely places, like the western United States, as
well as in IFR flying needing adequate range and reserve. Certainly, if maximum
utility is desired, an airplane’s manufacturer should strive to provide for the
greatest possible fuel capacity when the airplane is originally designed.
The second is to fly within the airplane’s fuel capacity by limiting the length
of flights. This is restrictive, of course, because sometimes weather covers a big
area that doesn’t allow a short-range airplane any alternates. Then there’s only one
thing to do: sit and wait for better weather.
Instruments and Autopilots
What else does the airplane need? Instruments to fly by, arranged in a good,
useful fashion. Decades ago, panel layouts had instruments and radios stuck about
cockpits in appalling, hit-or-miss manner. Thankfully, however, the industry
began to cure this in the later 1950s, with the “basic T” primary instrument
layout. So most airplanes today, save some older classics, have their flight
instruments, as well as communication and navigation equipment—avionics—in a
standard, close together useful placement. Good instrument flying requires
constant visual scanning by the pilot, so logically, the shorter the distance a pair
of eyes needs to travel to scan an instrument panel, the better.
The basic key of instrument flying is to keep one’s eyes constantly roving
—“scanning”—over the important flight instruments. When a pilot flies weather,
the technique of flying by instruments should be so well developed that almost all
attention can be devoted to the problems of weather, air traffic, and flight.
However, with today’s integrated avionics and flight instrumentation systems, the
workload is even higher. These demands are challenging for a hand-flown, single
pilot aircraft, so ideally, an automatic pilot does the flying job. Not all general
aviation airplanes are equipped with autopilots, consequently requiring careful
consideration before flying into a busy airspace environment. Even VFR, where
basic hand-flying takes excessive workload, keeps our eyes inside the cockpit, not
looking out for traffic, and this is especially challenging for less experienced
pilots. If one is planning to consistently fly in busy airspace, even a very simple
modern autopilot is not only helpful and a great enhancement to safety, it’s pretty
much imperative.
Autopilots have reached a level of sophistication that can be of tremendous
benefit to all aircraft. They are light and reliable because of today’s electronic
wizardry. The simplest autopilots, referred to as single-axis autopilots, include
automatic roll control, heading select, course interception and following; this can
be very helpful in today’s busy ATC environment for both IFR and VFR and in
many cases, should be considered mandatory. If we add a pitch function that
maintains climb and descent rates, as well as holds altitude, that’s a dual-axis
autopilot. Three-axis adds a yaw damper, which helps stabilize yaw control of an
aircraft, usually required in jet aircraft due to swept wing and other effects. In a
light aircraft a yaw damper prevents sashaying through turbulence like a hula
dancer. It facilitates a better flying aircraft and helps reduce the retching
passenger syndrome.
We now see digital autopilots that combine the current world of integrated
avionics and flight instruments, even in light aircraft, and these systems are a
pretty close match to many airline or corporate cockpits, except for automatic
throttles—at, of course, commensurate prices. These autopilots easily do all the
basic flight chores and then add programmed navigation in all phases of flight,
including complex approaches. Modern airline and some corporate aircraft go that
last step to automatic landings, using automatic throttle control—autothrottles—
kicking out crosswind crab, landing, and rolling down the middle of the runway
until the aircraft stops with automatic brakes, or the system is disconnected with
the pilot back to good old manual taxiing!
The autopilot, when operating normally, can do the manual labor of flying,
while allowing the pilot to manage the flight, which importantly includes
monitoring not only autopilot system function and navigation but the aircraft’s
basic flight parameters. This is important, because not only can autopilots totally
fail, they can do so partially, offering subtle failures, such as tracking a course
improperly, sneaking off altitude hold, exhibiting unexpected altitude captures or
failures to capture an altitude at all, and many more combinations. These simpler
failures can be easy to miss, which is why we must constantly monitor basic flight
parameters and electronic annunciations that verify the autopilot is conforming to
what we are asking it to do. Also, some autoflight systems do not necessarily have
blatantly obvious warnings of failure. The newer autopilots, connected to
integrated navigation systems, are excellent, but now enter the world of the pilot
having to program the route and altitudes properly, which feeds the lateral and
vertical navigation of these advanced autopilots. This means the autopilot, once
placed into action, chases assigned altitudes with Vertical Navigation (VNAV ), as
well as courses and headings with Lateral Navigation (LNAV ), as we have
programmed them. Consequently, if we mess something up, the airplane is going
to do it—it just reacts to what it’s told. Usually, surprises in automatic flight
systems are due to pilot programming errors, whether it be a simple autopilot or
the fanciest Electronic Flight Instrument System (EFIS) arrangements. It is
important, from the first day we begin learning to fly automated cockpits, that we
learn, or develop, some form of single-person redundancy—check and crosscheck—for programming and flying these systems.
All this means a pilot should frequently check that the autopilot is behaving
properly, whether the autopilot is simple or complex. This is a matter of not only
scanning against raw data—attitude, altimeter and indicated airspeed—but also
checking that we’re flying the programmed flight paths and navigation. Overall,
however, these systems usually work beautifully, offering better pilot awareness
as well as safety, because the autopilot relieves the high concentration of manual
instrument flying, making scanning of a flight’s overall operation easier and
better.
In the complex world of instrument flight, an autopilot is almost a
requirement; someday, they will probably be standard on all except pure sport
airplanes, but we even see quite nice autopilots on homebuilt and Light Sport
Aircraft (LSA ). These autopilots are certainly very desirable, especially if we use
programmed navigation and fly in crowded airspace requiring precise flight for air
traffic demands; they also give us time to look outside for other aircraft, terrain,
and, yes, weather. They turn a busy hand-flying task into a more relaxed
experience in which the pilot is potentially in better command of the situation and
always ahead of the airplane. The lower a pilot’s experience level, when operating
in demanding airspace and with more complex instrumentation systems, the more
an autopilot becomes a serious need. Of course, a good copilot can also be a
clever choice. However, an autopilot should never be a crutch for a pilot who
lacks basic flying skills. This, however, becomes an ironic quandary. On one side
we need autopilots to reduce the workload from more complex instrumentation
and crowded skies, but on the other side they prevent pilots from learning and
maintaining proficiency with good basic hand-flying skills. We take a more
concerned look at this in later chapters, when discussing instrument proficiency
and flying technically advanced aircraft.
Where the Instruments Live
Our instrument panel layout has to display itself in some logical and useful
organization. Each panel arrangement presents its own problems. The space
available, control-wheel location, windshield height, and other such factors dictate
how instruments can be arranged, but regardless of these problems, the primary
flight information instruments need to be grouped closely together, and easy to
find and comprehend.
Almost as important as the type and condition of instruments is their location.
The basic T system of layout is used worldwide, no matter if they are good old
round-dialed instruments—affectionately referred to as “steam gauges”—or
modern electronic flight instruments displaying primary flight data orientated the
same way. It has been proven for over half a century of flight and is found, in
principle, on every airplane designed for instrument flying from light general
aviation to the most modern transport aircraft. This system positions the artificial
horizon top center and the directional gyro or Horizontal Situation Indicator (HSI
) directly below it. The altimeter is placed right of the horizon, and the airspeed
indicator is to its left. This location of the artificial horizon—the attitude
instrument—in the most prominent and easy-to-use location is a testimony to the
importance of attitude flying. With round-dial instrumentation, we find the turn
coordinator or turn and bank on the lower left, Vertical Speed Indicator (VSI ) on
the lower right, and the whole compliment is referred to as a “six-pack”
instrument setup.
The important point is that the instruments should be as nearly in front of the
pilot as possible, and they should be in clear view and not hidden by the control
wheel or anything else. Flying the Airbus side-stick system, now seen on some
popular general aviation aircraft, leaves a wide-open view of the instrument
panel; one can even have a laptop writing desk to keep notes.
The basic T instrument location derives from developing an easier to scan
instrument panel arrangement, which in past decades referred a lot to hand-flying.
However, even when flying on autopilot, we still need to scan and monitor
instruments with the same efficiency as when flying without autopilot. As
mentioned, the key instruments are the Artificial Horizon, o r Attitude Deviation
Indicator (ADI ), for bank and pitch reference, and the Directional Gyro (DG ) for
heading. Round-dial directional gyros are fast becoming of sketchy accuracy
when flying in action-packed airspace, because we have to constantly worry about
resetting the DG. Before today’s digital electronic instruments, the big deal for
DG replacement was the HSI, which is a big advance and help, because it has
heading and navigational information all together. Also, the heading is slaved to a
remote pickup and stabilized, so one doesn’t have to constantly worry about
resetting the DG. Airspeed, vertical speed, and altimeter are really reference
instruments, and their action is a result of things that appear first on the artificial
horizon and directional gyro.
If the key instruments are watched closely, the airplane never gets a chance to
go very far from the “straight and narrow.” Frequent scanning and immediate
correction of excursions from the desired flight path give the feeling that one has
the airplane in a narrow corridor, boxed in on all sides, unable to escape and fly
off on its own.
Because rapid scanning prevents the airplane from getting far off course, any
correction the pilot needs to make will be small and therefore easy. Problems start
when a big bank or pitch angle is allowed to develop. If this happens, the heading,
vertical speed, airspeed, and altitude go off, and the pilot has a handful trying to
get the airplane back where it belongs. Scanning is not difficult if practiced. Small
corrections and never allowing the airplane to wander far make flying simple and
relaxed.
Clean and capable classic round-dial, IFR-capable instrument panel. This 1965
Piper Cherokee is a nostalgic beauty, but is fully capable today with its clean and
concise panel nicely retrofitted with a good communication and navigation radio,
transponder, audio panel, and the real gem, a Wide Area Augmentation System
(WAAS)-capable GPS/radio combination. This airplane can fly the many new
GPS-based instrument approaches and has precise area navigation with top-shelf
accuracy. With a good hands-on pilot of sensible cockpit discipline, this airplane
offers a lot of safe and enjoyable utility. (PHOTO BY RUSSELL J. KELSEA)
A top-notch, modern electronic Primary Flight Display (PFD). It is clean and
concise, with excellent but not cluttered features. Considering the basic T
instrument arrangement, this PFD’s clear design shows the same layout for
primary instrumentation; compare it with the round-dialed instrument panel
pictured above. Far left is airspeed, center is the ADI, with the altimeter to the
right and the Electronic Horizontal Situation Indicator (EHSI) below the ADI.
The only real difference is placement of the VSI to the right of the altimeter, and
the standby instrument gyro is elsewhere in the panel, depending on the design.
(PHOTO IMAGE COURTESY OF AVIDYNE CORPORATION)
It is very important that the pilot be well versed in attitude flying. There are
reams of information and instruction available, and an instrument pilot should
take advantage of them to become a good attitude pilot. Attitude flying, in one
simple example, is the difference between attempting to maintain a specific
airspeed by chasing the airspeed indicator, rather than by keeping the horizon bar
in a position that will give the specific airspeed desired. If speed is too high, the
nose is raised slightly with reference to the horizon, thus producing a small but
positive airspeed correction. Practice soon teaches what attitudes will provide the
desired airspeeds, heading changes, descents, and climbs in small, easily
controlled increments. More importantly, it will help keep airplane movements
small and prevent large oscillations that are difficult to recover from. Well-
arranged instruments, combined with good scanning and attitude flying, make
instrument flight precise and simple.
For many who learned on round-dial instruments, the VSI was very much in
the loop, and today may be an overlooked instrument. Primary instruments were
originally a turn and bank, airspeed, altimeter, wet compass, and VSI, but no
artificial horizon, so learning those basics made the VSI a useful part of flying.
The VSI in today’s high-tech world still has merit, especially when hand-flying
without a flight director or if we’re down to basic standby instrumentation from
primary instrument failure. If the VSI is steady on zero, there cannot be much
wrong with the airplane’s flight; vertical speed cross-checked with the DG is an
easy, quick look that things are okay—we’re straight and level. A good vertical
speed instrument, whether the “old-fashioned” round-style or one on a modern
PFD display, is a valuable instrument to catch your eye. When the VSI starts up or
down, we had best take a look at the other instruments and see what’s going on. It
is also valuable in judging altitude level-offs, by monitoring excessive climb or
descent rates. On approaches with vertical guidance it helps us judge head or
tailwinds by comparison to descent rates versus groundspeed. It can also tell us if
the air mass in which we’re flying has excessive vertical action, such as in gusty
conditions and potential winds-hear issues. Earlier VSIs had some lag time, but
the new ones on electronic instrumentation are quicker, like the Instantaneous
Vertical Speeds (IVSI ) of higher-performance aircraft, which enhances a VSI’s
value. A glance at the VSI and heading, especially in compromised flight, can tell
us a lot.
We Can Keep It Simple
Despite today’s obsession of electronically displayed and enhanced instrument
panels, we need little instrumentation to stay upright and do a fair amount of good
instrument flying, if we are properly trained and practiced. A little history helps us
dispel any misunderstanding that without the fanciest gadgets we’re doomed.
So what kind of instruments does one need? The extent and sophistication of
the instruments is determined by the amount and kind of weather a person is going
to fly. A pilot can fly some pretty awful weather with quite simple instruments,
but that’s a very busy pilot, and the job accomplished won’t be a neat, precise
one.
My own (RNB) instrument flying began in 1931 with an airspeed, vertical
speed, and a turn and bank. I taught myself how to use them by following a little
pamphlet-sized book called “Blind or Instrument Flying?” which was written by
an airmail pilot named Howard Stark, one of the important pioneers of instrument
flying. Charles Lindbergh credited Mr. Stark’s writings as guidance to his learning
instrument flying—and one of the key reasons he made it to Paris from New
York, on his famous 1927 flight in his “Spirit of St. Louis.” His only attitude gyro
to keep him upright and from losing control, as he flew through hours of clouds
and dark over the North Atlantic Ocean, was a little 2¼ inch diameter turn and
bank instrument.
I flew actual instruments, too, but it was all restricted to climbing up through
or flying on instruments toward clearing weather. It was done without radio by
simply holding a heading. This wouldn’t be possible today in most parts of the
world, because of airways and traffic, but back then there wasn’t any traffic, nor
any airways either.
A Little More to Do a Lot
From that simplicity, in 1937 I graduated to a Douglas DC2; the only addition to
its instrument panel over my little two-place, 90 horsepower Moncoupe’s panel
was an artificial horizon and a directional gyro. Along with this, there was, of
course, a radio to follow beams and a loop turned by hand to read bearings, which
said the station was at one end of the bearing or the other, but not at which one,
because the loop didn’t have direction-sensing capability.
With this setup, we flew weather, lots of weather. The landing minimums at
Newark, New Jersey, in 1937, were a 300-foot ceiling and ½-mile visibility!
Takeoff minimums were 100 feet and ¼-mile! It wasn’t done very sophisticatedly,
either. We flew the radio beam toward the station, which was down in the Newark
meadows near Elizabeth, New Jersey. We crossed over the center of the station,
called, in the slang of the day, the “cone of confusion,” at 800 feet, chopped the
throttles, shoved the nose down, and descended quickly to 300 feet; then we
looked into the black night for a row of red neon lights that led to the black
runway. What’s so surprising, in retrospect, is that we did it often and
successfully. Of course, a DC2 could fly at 80 miles an hour; that makes a big
difference from a jet that you don’t get under 135 knots.
All this is to show that a lot of weather can be flown with a primary flight
group, an artificial horizon, and a directional gyro. We did, in those times, do a lot
of practicing using the primary flight group only; needle, ball, airspeed, vertical
speed, and every instrument check we took included an approach using only the
primary instruments. I’m afraid this isn’t done as much as it should be today.
Personally, I like the turn and bank indicator over the turn coordinator and believe
the flight cues more true using the turn and bank, but perhaps that’s all because I
was “raised” on a turn and bank. When I bought my Cessna, it had a turn
coordinator, which I promptly replaced with a turn and bank. I just don’t feel that
the artificial horizon look of the turn coordinator is relating truthfully to turn.
Today, however, many light aircraft autopilots are sensed from turn coordinators,
so they must stay. Either way, we have to practice and be competent flying
whatever backup instrument flying displays we have, whether turn coordinator,
turn and bank, or artificial horizon, possibly tucked into an obscure corner or out
of the normal panel scan.
Our old artificial horizons did about what today’s can. The directional gyro
was the bore, because, like simple DGs of today, it didn’t have any north-seeking
ability and needed to be set to agree with the compass. Gyros precess and must be
set frequently. They must be set when the airplane is level and not turning, with
the magnetic compass settled down so that it’s reading accurately. In rough air,
while working on holding a course, this can be difficult to do. Some gyros precess
more than others, depending, generally, on the condition of the gyro. If it is well
maintained and periodically overhauled, and if the vacuum source, in the case of
vacuum instruments, is set to give a constant value of vacuum, a gyro can hold a
heading for 15 minutes or more without much attention. A point to remember is
that once a gyro starts to precess, the rate of precession increases the more it
precesses; so it’s wise to reset a gyro before it gets too far off. It is wise, also, to
rate your DG by keeping a record of its precession rate. Set it carefully on a
smooth day, then fly for 15 minutes and reset it, noting how many degrees it was
off from the previous setting. Keep a record, and when the rate becomes too high
—about a 10-degree error in 15 minutes—it’s time to have it overhauled. The
manual DG has stuck with us for decades, and again with a round-dial, older
panel we may still have a precessing DG. So now we know how to handle it.
Things Can Be Better
In modern instrument flying, which requires precise following of airways, a DG
may add appreciably to the cockpit workload, and as mentioned earlier, it might
not be up to the accuracy we need for more crowded airspace and their precise
demands. Instrument designers have cured the problem by wedding the directional
gyro and compass so that a north-seeking unit constantly keeps the gyro’s heading
adjusted for magnetic north. The important point is that once the gyro is set, the
pilot need never worry about resetting it; we call this a “slaved gyro.” The
heading information is always precise without the turning error, run ahead, and
hold back of a magnetic compass.
This intelligent type of gyro has been one of the biggest boons to precise
instrument flying, and it reached aviation technology at about the time that heavy
traffic and more narrow airways called for better flying. This, now, is the HSI we
talked about; it’s one of the first “extra” items we would add to upgrade a
traditional, round-dial instrument panel with a nonslaved DG. Today we can take
another jump over nice mechanical HSI units with an Electronic Horizontal
Situation Indicator (EHSI ) or go further to a Primary Flight Display (PFD ),
which includes both the EHSI and Electronic Attitude Director Indicator (EADI )
, with more parameters of information. Their sensing is derived from a nice digital
Attitude and Heading Reference System (AHRS ) that replaces the more
maintenance-sensitive mechanical gyros, wires, and slaving units. Added to this is
a n Air Data Computer (ADC ), which takes standard pitot and static inputs,
refines their errors, and produces very accurate data, allowing more precise
instrumentation, autopilots, and related guidance. Sometimes these two devices
are combined into one unit, being called an Air Data, Attitude, and Heading
Reference System (ADAHRS ); an acronym field-day. These marvelous little
computers are what makes the new electronic instrumentation so concise and
capable, all with new levels of accuracy, reliability, and lightweight design for
smaller aircraft. This type of accuracy has been standard with larger aircraft like
airliners and corporate jets, which also use air data computers, but instead of
AHRS for their gyroscopic needs they have historically used Inertial Reference
Units (IRU); however, to reach today’s average GPS accuracy for navigation, the
civilian IRU navigation systems had to be tightened with GPS interface.
To sum up at this point: The minimum one needs for instrument flight is the
“primary flight group” (the historic name for T&B, airspeed, altimeter, VSI and
wet-compass), plus an artificial horizon and DG. With this, one can fly
instruments and shoot low approaches; with the addition of a slaved gyro or HSI,
however, life becomes easier—and much easier with an autopilot.
Even Better
Technology took us further by adding intelligence to the artificial horizon,
directing us with a “command” cue in the artificial horizon, to our desired course,
usually an ILS’s localizer and glideslope. To explain a bit, if we fly an ILS with a
horizon and DG, the localizer needle is located in another instrument, either a
separate dedicated one or an HSI. As we fly headings toward the localizer, once
we’re on course we try to find a heading that will keep us on it, by a process
called bracketing. How much to turn and when to turn is a matter of skill and, to
some extent, guesswork. As Dave Little, an American Airlines captain in the early
years of the airlines, who had done a great amount of research in instrument
flying, said: “Flying down a localizer this way is like following the white line on a
road by watching it through a hole in the automobile’s floor.”
Now we have command bars in artificial horizons that have computed
information fed into them. They discover how far off course one is, what drift
there is when an airplane is wandering from the course, and then say, “Turn now
and this much.” The information is presented in such a way that one has only to
follow a little airplane command symbol or bar, superimposed on the horizon,
matching one with the other, and by so doing a pilot stays right on localizer and
glide path. It is called the “Flight Director.” The pilot still refers, although only
periodically, to the basic localizer/glideslope instrument to make certain that the
flight director is doing its job.
Occasionally, there are times when a flight director command just doesn’t add
up to what we see on our raw data. (Raw data is what the ILS needles, airspeed
and altimeter, plus indications off the basic attitude flight instruments are telling
us. This lets us verify if the little computer that guides the flight director is doing
its thing properly). When there is any doubt between raw data and the flight
director, go with the raw data. This is called “flying through” the flight director;
following instead that accurate raw data versus erroneous flight director
commands. This can get a little confusing, and requires strict discipline, in that we
are fighting the urge to follow the easier to fly flight director bars or cues, while
w e must focus and fly the accurate raw data. This, we may add, only does any
good if we know the attitudes and power settings necessary for whatever
parameters we need. That’s why we need to first fly an aircraft without augmented
information such as flight directors, allowing us to establish basic knowledge of
what attitudes and power settings give us those needed performance parameters.
When equipment of this sophistication came aboard jet airliners in the later
1950s, pilots were allowed to shoot hand-flown minimums as low as 200 feet and
½-mile visibility. The flight director was required for these approaches, but today
the hand-flown approaches of professional operations are often limited to ¾-mile
visibility; below that the approach is required to be flown by the autopilot, which
we call a “coupled-approach.” Obviously, if the flight director and autopilot are
not working, minimums are higher and this is one reason why airliners carry
duplicate systems. However, when flying privately, we can fly to 200 feet with a
½-mile visibility—assuming the approach is approved for such—with just an ILS
indication in a separate VOR/ ILS indicator; an HSI or flight directors is just icing
on the cake. These minimums are known as Category I (Cat I ), with 200 and ½
the lowest criteria for Cat I, assuming the approach is approved for these lowest
minimums. It is something to think about for our personal flying, considering
professional operators with often better equipment, more experienced pilots, and
constant currency from operations and training, have more restrictions. In any
event, with equipment giving us both lateral and vertical guidance, whether it be
an ILS or GPS-based approach, it is easier to fly a 200-foot ceiling with a ½-mile
visibility with that equipment than a 400-foot ceiling with a mile-visibility
without it.
The computer data fed into these flight director systems is often the same as
that given to the automatic pilot when it is set up for making low approaches; if
the airplane is equipped with both, one system is used as a check against the other.
When we start going to lower minimums and automatic landings, such as in
airliners and higher end corporate aircraft, there are usually two or three
autopilots, with commensurate comparison computers and displays of operation.
Three may seem excessive, but when you are comparing two—whether autopilots
or something else like an ADI—there’s quandary as to which one is bad. But with
three, then you get a majority decision. Outwardly, it seems very complicated, but
in reality, these systems work precisely and rarely with a flaw. However, despite
the redundancy, these operations still must keep an eye on raw data information,
which in advanced instrumentation is usually displayed on the EADI and/or PFD.
The flight director approach combined with autopilot came to our experience
with the Boeing 747 in 1970. This reduced minimums at certain airports to
Category II (Cat II ) of 1,200-foot visibility and 100-foot ceiling. Cat II is flown
with an autopilot “coupled” approach to 100 feet, without the requirement of
autothrottles or autoland, which if without upon reaching minimums the pilot
disconnects the autopilot and lands manually. This is a successful procedure, and
when reaching 100 feet, most of the approach lights are behind us, which is why
Cat II/III runways have Touch Down Zone Lights (TDZL ) physically in the
runway. The only task was clicking off the autopilot, flare for landing and the
procedure works great. However, despite the slight bruise to aviator ego, if an
airplane has autoland capability, the best deal is to use it.
Category III landings, today, have whittled minimums to no ceiling
requirement and 300-foot (75 meters) visibility, but of course they are totally
automatic, with autoland and autothrottles; an elegant process. By the way, this
visibility is measured along the runway with three and sometimes four Runway
Visibility Range (RVR ) devices, called transmissometers. Each unit has little
light-sensitive sensors that analyze light reception, which through computerization
is processed into an RVR reading measured in feet or meters, depending on where
in the unit-world it’s located. Control tower visibility is usually nil, being stuck up
high in the fog. There are actually three levels of Cat III operation—IIIa, IIIb and
IIIc. All visibility rated, IIIa is 600 to 700 feet or 200 meters, IIIb over 300 feet or
75 meters, and IIIc is plain old zero! One of the reasons IIIc, or zero visibility
minimums have yet to happen operationally is a function of finding taxiways and
a parking place in the fog. There are required centerline-lighted taxiways,
specifically illuminated, that at least guide us off the runway and down the
taxiway away from the runway environment. The rest is an interesting game of
carefully following airport diagrams, checking headings, and squinting at taxiway
markings. It keeps two or more pilots pretty busy and sometimes a bit edgy. One
day in Paris, on one of those foggy European mornings, two aircraft came nose to
nose as they oozed through the murk. They saw each other, stopped—usually in
such lousy visibility we taxi with at least the aircraft’s taxi lights on—then stared
at each other for nearly an hour waiting for tow trucks, also lost in the fog, to find
them and untangle the mess.
The many approaches we’ve made to these low minimums were easier, more
relaxed operations than flying by hand to a much higher minimum. The autopilot
does the work and we have lots of time to scan the cockpit and double-check
instruments. You have an understanding of the entire action, rather than being
mesmerized by the few instruments that one uses to keep in the slot when flying
by hand. When the runway lights come into view, there’s no worry about sensory
illusions and getting too low and below glideslope on the visual part of the
approach, because we’re there! Right at the runway, and in a few seconds rolling
down the centerline. It’s the way to do it. However, and again, always remember
that during these sophisticated approaches, a pilot should double-check the raw
data, checking to see what the approach’s primary guidance needles and the flight
instruments are saying, making certain that the fancy electronics are on the ball.
Overall, Cat II/III is not usually a general aviation operation, instead mostly
for airlines and certain corporate aircraft. However, they are worth understanding,
especially because these lower minimums instigate a great deal of the technology,
techniques and standards we use in all our instrument approaches.
Departures are another area where the FAR’s tell commercial operations they
have minimums; usually visibility, but at times ceilings due to terrain issues.
What’s important with any instrument departure is having some sort of valid
departure procedure that keeps us clear of obstacles and terrain, as we clamber for
altitude. This can become a gray-area when operating from some airports, because
if not operating commercially we can depart in very poor visibility—for that
matter, nil, if one is really that itchy to go. The prudence of this varies with each
event, and crosses swords with the real benefit of general aviation which is having
the ability to use thousands of local airports. However, when the weather is lousy,
the discipline of low-visibility operations is the same, whether an airliner in
Seattle or a light aircraft at a local airport on a foggy morning. If we’re taking off
in low visibility and don’t have adequate runway lighting, and especially
centerline lights, the heading (DG, HSI, etc.) becomes an even more important
reference. We reference it constantly as we rush down the runway, eyes in and out
between DG and what we can see outside. However, once we rotate the airplane
we’re on that attitude indicator, with reference to heading, airspeed, and altimeter
to make sure we’re climbing, and under control.
As a side note, even in the world of high-end aircraft sporting excellent
equipment, initial rate of climb for landing gear retraction is altimeter-referenced,
due to post rotation error with some VSIs. In the first years of the big jet airliners,
one flight was quick on the gear and instead of climbing away towards another
glamorous, early jet-era flight, they ground to a halt at the runways end.
Fortunately, nobody was hurt, but it was an expensive lesson that kept the sheetmetal shop busy for quite a while. Around the time I (ROB) soloed our Cessna
120, in the summer of 1965, my father climbed in one day and said we should do
an instrument takeoff. Confused—it was a lovely clear morning in eastern
Pennsylvania—he explained the process and soon we were at the end of the grass
runway at Van Sant Airport, which kind of rolled and leaned, with an instrument
hood over my eyes and the WWII-vintage DG and artificial horizon spun up, set
and ready. We trundled down the runway and somehow kept the little tail wheeled
Cessna straight, gingerly easing into the air, with its 85 horsepower clawing into
the summer sky. As those years of innocence turned into an aviation career, when
pointed down a fuzzy runway in lousy visibility, with all the formality of
equipment, crew, briefings, and procedures at hand, I’d remember that moment at
Van Sant’s, my father and I squeezed together in our little 120’s narrow benchseat.
The Future Will Be Even Better
We have reached an era when even single engine general aviation aircraft can
match navigation and instrumentation on par with airline and corporate aircraft.
Certainly there are performance and environmental advantages to bigger and
higher performance aircraft, but overall, general aviation offers impressive utility.
With the hopefully successful Next Generation Air Traffic System (NexGen) not
far away, these well-equipped light aircraft will fit into the envelope just fine.
When the industry honed the integrated avionic and autoflight systems with
autothrottles, it allowed ultimate efficiency of fuel burn and flight path
orchestrated through the electronic brains of Flight Management Systems (FMS).
General aviation EFIS systems, with integrated autopilots, have just about
everything these large aircraft offer—and sometimes more—but without
autothrottles. For now, however the pilot with a nice six-pack of round-dial
instruments (airspeed, attitude indicator, altimeter, VSI, and preferably an HSI,
with adequate navigation and communication) has a fine instrument-flying
platform. It may sound untrendy to suggest this, but trendy instruments are
expensive, so our guess is round-dial panels will be around for quite a while.
When an upgrade is possible, it can be done whole hog, with a fully integrated
glass cockpit and autopilot, or more frugally, as upgrades to a nice approved
GPS–WAAS system and maybe a simple autopilot. (WAAS means Wide Area
Augmentation System, which allows IFR accuracy for a GPS equipped aircraft by
using remote ground stations to tighten the GPS signal accuracy; at this writing,
within three meters 95% of the time.) There will remain limits to the amount of
instrument flying possible, just as the pilot with a little more equipment is limited,
though not quite so much, and the one with everything is limited even less. The
equipment, humble or extensive, must be used properly, with the pilot’s
proficiency honed to a fine edge through both knowledge and practice.
A beautiful example of a full-house, Technically Advanced Aircraft’s (TAA)
instrument panel, including a good autopilot. The standby instrumentation is
behind the left horn of the “captain’s side” control wheel, which would be in clear
view of the pilot when seated. (PHOTO IMAGE COURTESY OF AVIDYNE
CORPORATION)
The Protected Airplane
A new twist available in conjunction with aircraft having advanced autopilots is
the introduction of “smart” autopilots that, while the pilot is hand-flying, input
increasingly heavier control force inputs and/or corrective pressures, when the
aircraft begins to exceed predetermined aircraft parameters. They are not only
reminders to the pilot, but also coax a pilot back to normal flight with a selfrighting tendency.
Then there is a button that when pushed will “right” the aircraft to straight and
level flight, assuming it was pushed before the aircraft was too far out of control.
Impressive technology with definite value, but these technologies should not be a
crutch for a pilot lacking basic flying ability. However, because these protective
systems are autopilot-based, autopilot failure reverts the aircraft to nonaugmented
hand-flying characteristics, so the pilot is back to square one; a shock if a pilot is
dependent on these systems. There is no way around the fact that we will always
need to have competent hand-flying skills. Nor can we fly aircraft assuming
failure possibility is so remote we can take the risk they won’t fail. We can’t think
that way in aviation—again, we have to be capable of handling the worst scenario
that is controllable with of the lowest common denominator of equipment.
As to instrumentation features, we have PFD displays now offering “synthetic
vision,” computerized terrain presentation derived from GPS data, and “enhanced
vision,” which sees through clouds and dark. These are magnificent additions, and
potentially quite useful, but again are usually not approved primary flight
information, such as flying over terrain in instrument conditions or finding a
runway below minimums. However, on high-end systems of mostly corporate and
military aircraft, we see these systems being integrated into low-visibility
operations—so, we can only surmise what the future may bring.
Oh yes, while not an instrument, we feel the ballistic parachute is worth
mentioning. It is a unique and helpful feature, especially for events we can’t do
anything about, such as an engine failure at night over bad terrain or mid-air
collision; but realizing, for many reasons, the parachute is still not always going
to be successful. Most importantly, it is our opinion that a ballistic parachute
should not be there to save a pilot from the inability to fly an aircraft in conditions
their ratings and judgments place them, be it something as simply inappropriate as
running out of fuel, or maybe very demanding such as turbulence, icing, or
thunderstorms.
In thinking of GPS navigation, if we’re depending on it, and not following
with a map, and the GPS and/or display quits, where are we? If it’s a nice, sunny,
clear day, we have time to flail around the cockpit for that backup sectional chart
or handheld GPS. But dark and IFR, especially if our problem is electrical and
we’ve lost that nifty autopilot, among other things, the situation can turn into a
real mess. You’ll have to work that one through for yourself, turning on a backup
electronic device or using a chart. If your panel doesn’t have emergency lighted
standby instruments, you’ll have light from that flashlight between your teeth, as
your hands are busy flying the airplane. Either way, in much of our general
aviation world, we should consider having a sectional chart nearby, folded to our
route and between the front seats. By the way, what happens on the airlines as to
IFR charts? With glass cockpits, we went through that chart thing of keeping them
in our flight bags. Then, after some interesting fandangos occurred that couldn’t
be handled by fast typing on the FMS, the requirement was to keep a chart nearby,
ready for action. It will happen—trust me.
So, it is imperative for the pilot with the fancy equipment to maintain
proficiency with the simpler equipment, namely the minimum we use for a last
resort backup. The primary flight group (airspeed, vertical speed, turn coordinator
or turn and bank, and in these days an artificial horizon) is the most reliable,
always being the standbys if the other instruments fail. For more than 75 years, the
turn and bank, and later the turn coordinator, has been found on every instrument
panel with which any instrument flying was done, from Cubs up to airliners and
jet fighters. They are beginning to disappear, being replaced by a standby horizon
and some really nifty electronically displayed units, with self-contained airspeed,
altitude, and longer lasting backup batteries exceeding the anemic 30-minute
required minimum. Many general aviation airplanes still have turn coordinators or
turn and banks; we weigh in with the opinion that the turn coordinator is goosier
to fly than a turn and bank, but both keep working, no matter what the aircraft’s
attitude. If a turn coordinator or turn and bank is on your instrument panel—
indicative of a round-dial, six-pack instrument setup—it’s a good idea to cover the
horizon and DG/HSI now and then, and have a practice session with only that
rate-of-turn instrument. Remember that turn coordinators are not artificial
horizons, but gimmicked-up turn indicators, and should be flown as such.
Without the ability to successfully hand fly our standby gyro instruments,
redundancy to controlled instrument flight is totally blown. The result is simple—
loss of aircraft control and tragedy, instead of safe landing in a flyable airplane.
Besides its necessity for survival, staying current with standby gyro instruments is
both an excellent airborne and simulator exercise, its visceral function teaching
superb sense of aircraft control while flying instruments. It makes us far better
pilots, even when everything is working normally.
Today’s computerized glass cockpits with integrated avionics are wonders to
behold and do impressive things, but these systems are still subject to failure and,
because of their complexity, a human can improperly program the system. Pilots,
for a long time, will be required to monitor that all is well and the simple facts of
where we are, how high in relation to terrain, and the airplane’s flight condition.
It’s wise to remember that the pilot is ultimately responsible for avoiding the
terrain and guiding the airplane on the path it is supposed to follow. Some
computer people give the impression that airplanes can be flown entirely by
electronic systems, doing a better job than humans. This is pretty much true, but
not in an unlimited sense. Ask the question, “Would you fly on an airliner without
pilots and only flown by computers?” The answer is usually obvious. So we must
always be skeptical and double-check our situation.
Power for Instruments
Instruments, however, are no better than their power source. Some are vacuumpowered and others electrical. It is required—and for good reason—to have an
alternate source for our primary attitude indicator system, in case this critical
source fails. This can be supplied in a number of ways, depending on whether the
failure is the indicator itself or the source that drives it. If we use a round,
vacuum-powered attitude indicator, it would be nice to have a dual vacuum pump
system or a multi-engine aircraft. To back up an instrument failure, as we’ve
mentioned, we include a standby artificial horizon or turn rate instrument run by
electrics, namely the battery.
Now, we have the marvelous electronic “glass cockpit” PFD screen, with not
only attitude indicator, but also displays of airspeed, altitude, VSI, trends of flight
path, heading, navigation, and so forth, from those separate little computers we’ve
mentioned like the AHRS and ADC. They live in the fuselage and use pitot, static,
temperature, sense the earth’s magnetic field, and figure out the aircraft’s attitude.
Throw in a GPS box and we have navigation. Then there are other little computers
to pull it all together, and figure out inputs for things like flight directors. All these
devices are little digital wonders, with amazing probability from failure,
especially as compared to mechanical gyros and all that’s related to them.
However, even with the reliability of these newer devices, the quantity and
combination of their installations create multiple opportunities for failure; a field
day for statisticians obsessed with failure-probability. The short story is that, it’s
nice to have second units of these devices and whatever else makes them tick, but
that isn’t cheap and adds weight. If we have a full integrated avionic system of
PFD and Multi Function Display (MFD) on the instrument panel, the latter
showing us navigation, engine and system indications, weather and is a backup to
our PFD, and vice-versa through split screens. Still, we need—by common sense
and regulation—redundancy to all the screens and/or little boxes, should they fail
in critical combination, so we’re back to the standby artificial horizon attitude
indicator; the standby choice for EFIS equipped aircraft versus the turn
coordinator or turn and bank.
But that’s not all! Because these EFIS equipped airplanes are all-electronic
operation, we need two battery sources, and some aircraft even have dual
alternators. Without an alternator and totally on battery power for the standby
attitude indicator, regulation says we need at least 30 minutes run off battery, but
that can go pretty quick if we’re in IFR conditions, need to find an airport and
shoot an approach, all on standby instruments and now being hand-flown because
the autopilot doesn’t work on standby electrical power. The only time we’ve faced
such an event was in the simulator. The most advantageous setup has us in touch
with ATC, who we call and declare a total power loss emergency, ask for vectors
to the nearest approach, which hopefully is an ILS if we still have such equipment
operating (we do in airliners and other advanced aircraft), and indicate we won’t
respond unless absolutely necessary. That saves battery. We want to fly a close-in,
tight approach, but not get so frantic we overdo it, get high and fast, and then have
to go around. If no close-by airport or approach, the process gets very interesting.
There have been some dramatic situations and accidents because electrical
systems lacked sufficient backup. The summary is that if an airplane is going to be
used for instrument flying, its primary attitude instruments, and the electrical
system should have a useful backup. It is also worth bringing along one of those
fine standby handheld VHF radios, some with VOR navigation, and a small
portable GPS; and some interesting back-up potentials off personal electronic
devices is coming along but with legality and reliability issues still in flux.
All this is quite a contrast to the system on my (RNB) Pitcairn Mail-wing,
vintage 1930, which had as my sole instrument flying gyro a turn and bank
powered by a venturi that was mounted on an exhaust stack with five tiny holes in
the stack just ahead of the venturi’s entrance. These squirted hot exhaust gas over
the venturi and prevented it from icing up; such a rig might not have been a bad
alternate source for the vacuum systems we use on our attitude indicators, but the
retrofitted electronic glass displays of today have certainly changed that path of
thought. These days, people might shudder to think of venturis sticking out,
causing drag, and getting iced up. But an interesting comparison is the extendable
Ram Air Turbines (RAT) that modern jets have for last-ditch hydraulic, and
sometimes electrical power. They automatically extend from the aircraft belly in
response to various criteria of total system loss, spinning a prop that drives a
pump. They are like the little wind-driven generators seen on some light aircraft
from the 1930s into the 1950s—good old common sense in a fancier package.
Other than gyro instruments and their power sources, we need to remember
the airspeed indicator and altimeter are “powered” by pitot and static tubes that
bring in pressure and static air. Because it’s very difficult to extensively fly
instruments without airspeed, we need to remember that even modern glass
cockpits also use good old pitot and static for their complex systems, so it’s
important to keep these sources clean and operating. Careful inspection is
necessary before flight to be certain that the pitot tube and static source are free. A
bad static source will affect the altimeter, vertical speed, airspeed, and some
pressurization systems. Among other things, mud daubers love to make little nests
in the end of pitot tubes. I (ROB) had one constructed in a Cessna 182 pitot, just
overnight in Far West Texas. That’s why we should cover pitots—which
obviously I forgot to do!
Among the other things airplanes should have when flying instruments is the
previously mentioned pitot heat. Airlines feel that pitot heat is so important that
they use it whenever they are flying; it is automatically actuated with engine start
on more modern aircraft. It’s important to check our aircraft’s manual on this, as
in some aircraft the pitot heat is modulated cooler on the ground (ground sensing
switches on the landing gear), while others are either full-on or off, which when
on without airflow from flight can burn out the heating elements. Either way, once
airborne, whether cloud or no cloud, summer or winter, it’s good habit to always
have it on, in case we need it and are sidetracked at a critical time. A temperature
drop can take place inside a pitot tube and produce ice or slush if there’s visible
moisture. Even water from heavy rain can cause an erroneous reading in pressure
instruments. Ice, of course, can knock out an airspeed indicator completely. Pitot
heat is a must!
If the static source is within the pitot head, then the pitot heat will take care of
it; if the static source is flush on the outside of the airplane, as most are today, it
will not be closed by ice, but it can be blocked by slush being thrown up from a
nose wheel and then freezing, or by human-made things, such as tape put over the
static holes during airplane washing or servicing. This can be very serious,
remembering some preventable fatal airline accidents from covered or blocked
pitots and static ports, as well as quite a few incidents with happy endings. With
today’s general aviation aircraft having complex electronic flight and instrument
systems, this is a situation we must heed seriously. Once you break ground with
plugged pitot and/or static, where some things are not working, false and
conflicting instrument indications show up, autopilots may or may not function
correctly, and it’s absolute chaos for the little electronic brains of EFIS-style
instrumentation. Then, as we try to figure out what’s wrong and focus on flying
very screwed up flight indications, it’s made more chaotic with warning bells,
horns, and lights signaling their confusion. In the dark of night or during focused
IFR in clouds, the solution is cool over chaos, while flying attitude and power off
primary flight instrumentation, until we’re back on the ground.
The FAA requires that the condition of these instruments be checked
periodically for leaks and deterioration of the tubes in the system. Instrument
flying is important in weather flying, and while a person may or may not be
proficient, all pilots can make certain the instruments they are using will be in top
shape and functioning properly.
Lighted Well
It is important to have the instruments lighted properly. With modern glass
cockpits, this has become much better, if not nearing moot. Again, however, we
still have a lot of fine flying with traditional instruments, so lighting is still of
concern. This means that at night the entire area of their dials should be
illuminated without any shadows. There should be no glare, and they should be
visible in a minimum of light. It should not be necessary to turn the lights up
bright or to have excessively bright lights in order to see the instruments. Some
airplanes we’ve seen require such bright panel lights to wipe out shadows on the
instruments that outside vision is impaired. The pilot is like an actor trying to see
the audience through bright footlights. The bright light not only cuts out what can
be seen outside, it also deteriorates a pilot’s night vision. Bright lights also have a
way of reflecting in windshields, so that as a pilot looks outside, the instrument
dials grin back from the windshield or side windows in a most annoying way.
On the subject of night flying, it’s worth realizing that night VFR flying is
instrument flying to a large degree; while a noninstrument pilot can legally fly at
night, a clear night with good visibility and some sort of horizon will be required.
It can be an awful shock for a pilot to leave the end of a runway and to be
suddenly enveloped by a pitch-black night with no horizon or reference to fly by!
If the horizon is not clearly defined, and there is any risk of clouds, it’s easy to
slip into a cloud and never realize it until all outside reference is gone and we’re
on instruments! An instrument rating is a strong safeguard. The VFR accident rate
is much higher during night flying than during day flying.
Paperwork and Gadgets Are Equipment, Too
Almost as important as an airplane’s instruments is the paperwork associated with
instrument flying. Whether we’re flying older electronic navigation of a VOR, a
line on a GPS screen with minimal position features or EFIS equipment with
terrain or maps underlaying the route, we need up-to-date maps, radio facility
charts, and instrument approach plates as an adequate backup. If we’re VFR, we
mean sectional maps that show terrain and important features: mountains,
elevations, rivers, towns, airports, and such. A few sectionals backing up IFR isn’t
a bad idea, either. Too often the only chart used is the radio facility chart, which
doesn’t show topographic features and a lot of other useful information.
Reference using real maps is important for many reasons, such as avoiding
mountains, locating airports in relation to towns, the water areas that may affect
weather—a host of things. For safer flight, maps are needed.
Added to paperwork comes today’s world of portable GPSs, personal
electronic devices, and numerous other gadgets to complicate the cockpit. With
them come wires and plug-in attachments. In short, whether we are using paper
data or these electronic items, we need to have a place for them in the airplane.
There’s nothing worse than charts, gadgets, and wires scattered all over the
cockpit. Good flying, instrument or visual, requires good housekeeping. This
means a little preparation in advance, before takeoff. For electronics, it is nice to
find good efficient mounts, preferably not blocking vision of the instrument panel
or outside visibility. To replace wires, anything we can work from a wireless
source is good, as long as the wireless connection is adequate for the level of
reliance we need from the device. For charts, we get them out as needed for the
flight, stack them in order, folded and secured (little clips are useful for this). We
probably use a flight-planning form and that, with the initial maps can be put on a
clipboard or some such device and kept close by so they are handy when needed.
A little pen/pencil holder is helpful; when the airlines got the then high-tech
Boeing 767s, despite all the gee-whiz stuff, an exciting cockpit improvement was
a set of pen/pencil holders.
Instrument charts should be treated the same way, and a clever pilot will have
a clip or some such gadget on the control column where the plate can be displayed
for reference while making an approach. It should be lighted. Going into big and
busy airports, there can sometimes be five or so charts covering the arrival
through the approach and then taxiing to parking. At faraway places, especially
overseas, where there are occasionally different procedures, a pad of sticky notes
can be helpful. Of course, today’s electronically displayed charts are a true
blessing after years of paper charts; but only if we can select them with minimal
“heads-inside” diversion.
The charts that we fly with, their course lines, frequency boxes, ball-notes,
little information boxes with an arrow pointing to where it applies miles away are
confusing and often difficult to read and interpret. There have been serious
mistakes made because of the way in which things are sometimes presented. The
papers we work from are a built-in hazard and should be treated as such. It is
necessary to study routes and terminals in advance, so you don’t have to do it in
the cockpit under poor light while bouncing around and trying to fly the airplane.
One way to catch errors that may result in using the wrong facility is to always
identify what’s been selected before using it. Every time we use a navigational aid
that has Morse code identification—such as a VOR or ILS—it should be
identified—period!
It’s a good plan to have a systematic and consistent procedure for studying
instrument approach plates, or the procedure as displayed on any appropriate
electronic displays, before flying the actual approach. We’ll talk more about this
in Chapter 19: Landing in Bad Weather .
With bigger airports, we find standard procedures for departures known as
Departure Procedures (DP ), which were called, and some folks still do call,
Standard Instrument Departures (SIDs ), their concept being consistent ATC
departure paths, crossing altitudes, and speeds for high-traffic density airports.
They create another chart that must be consulted before takeoff. It is important not
to be rushed into taking off until one understands what the SID/DP says and has it
firmly implanted in one’s mind.
Similar in concept to DPs are Standard Terminal Arrival Routes (STAR ),
except, of course, the STAR routes are for arrivals and again show the proper
routing, altitudes, and speeds. Combined with STARs are profile descents for
high-flying aircraft. Sometimes profile descents have their own special charts,
too. When DPs and STARs are presented and used electronically, like everything
else we load and fly electronically, we must verify they are correct as loaded into
our electronics. This comes up again in Chapter 14 on flying with technically
advanced aircraft.
All these are important, because there is lots of “fine print” that makes it easy
to miss some ambiguously worded instruction. It’s best to study these documents
carefully in advance, on the ground, and at leisure, and then to refresh one’s
memory before starting takeoff or descent, preferably in a relaxed, cruise portion
of the flight for the later.
Rather than hunting all over the chart when busy in flight, felt marking pens to
overlay routes, altitudes, or any other important bits of information are a big help.
Yellow is a popular color, but orange can work better at night. If you have red
cockpit lighting, red markings disappear. When I (ROB) started doing this I’d get
kidded that the map would eventually be all yellow. Close, but it seemed to work
and looked cool.
Go Fast Slowly
There’s a great tendency at busy airports for clearances to be delivered too fast
and followed by a rushed, “Line-up and Wait; be ready for an immediate takeoff
!” It comes in fire-hose fashion and tends to make people take off, half
understanding how and where to go when in the air.
The answer is simple: to heck with the tower. Sit there and study the
clearance. If you don’t get it, ask for a repeat. Then, when certain, ask for takeoff
clearance. It’s better to delay the takeoff than to rush off half-informed.
Admittedly, at a busy airport if we’re not ready we’ll possibly be shuffled out of
the takeoff order, instead of holding up everyone behind us, but if that’s necessary,
so be it.
In the cockpit, we need a place to write clearances and various things that pop
up during the flight. We want to copy weather and clearance changes, keep track
of fuel used, and write down a lot of other things. We need a clipboard or knee
pads strapped on, handy for the job, although today some carry electronic devices
tracking course, showing weather and so on, on these knee pads or specialized
mounts. A computer (electronic or manual “whiz-wheel”) and plotter, big enough
to see and handy at all times, are also indispensable pieces of equipment. When
we have electronic cockpits, we can sometimes get weather via data link, but
eventually it gets updated with new images and information, so unless you have a
super memory, writing things down as to following weather trends, changing
METARS for comparison to forecasts, and so forth, is sensible. Despite electronic
cockpits, there still is a place for paper and pen.
Good Housekeeping
All this is part of instrument flying, and keeping a neat, organized cockpit makes
instrument flying much easier. More important is the fact that a disorganized
cockpit makes instrument and weather flying much more difficult and increases
the possibility of serious mistakes. In setting up a cockpit, it is important to keep
it consistent, functional, and organized. Everyone develops quirks that work for
them, from clipboards with helpful reminders or checklists taped on them, to
where we position charts, writing gadgets, sunglasses, headset, and device wires
hopefully in some sort of neat, non-conflicting and organized position. Not only
does this keep us from forgetting things, it makes flight preparation and function
run smoother and more quickly without being rushed, both on the ground and in
flight.
This was never better displayed than with pilots rushing through frantic
changes of airplanes and gates during airline hub-and-spoke operations. The
beginning of cockpit preparation—often referred to as “making our nest”—came
from the infamous “black-bag” flight kits disgorging the manuals, maps,
sunglasses, headsets, writing pads, breath mints, special fly’n-hats, clipboards
festooned with personal checklists, and other personal items. There was even a
time we had our own oxygen mask face-pieces, which clipped into the system’s
headbands. Occasionally strings or rubber bands were connected between various
items to keep from forgetting them when the flight was over. After about five
minutes of flailing around, an unruffled calm began to settle over methodical
preflight of controls, buttons and knobs, electronic voices of tested warnings, then
the efficient process of monotone procedure review, checklist reading, and radio
banter. Suddenly, all was ready, and everyone was sitting there as if nothing had
happened, just waiting for the pushback clearance, with all tasks thoroughly
completed and understood.
A good pilot or flight crew knows the responsibility of proper preparation and
restraint over the whole operation; and that they own the parking brake.
Fortunately, in general aviation, we have less of this issue, unless we have an
impatient boss or fly by the clock instead of common sense.
So once organized and underway, a copilot can help reduce an instrument
flight’s workload; but even if we don’t have an official copilot (that is, a pilot
with ratings), we can often train a nonflying person to look things up and
sometimes even to handle the radio. This is best done by sessions at home, with
the pilot going over the airways, approach, and navigation charts with the nonpilot
and explaining what they are, how certain ones are needed in flight, how to find
them, how to add mileage, how to fold charts for pilot convenience and point to
where they are, how to dig out frequencies, and many other small but useful
duties. This can expand to learning the use of a computer for speeds and fuel
calculations, to basic radio work. However, when it comes to navigation, and
especially in today’s world of programmed navigation systems, the nonflying
person, whether a pilot or well-trained non-pilot, should always check with the
pilot flying before changing things, rather than surprising us with sudden route
modifications, erasing flight paths we’re flying, and so on. A little training of this
type may turn a willing spouse, child, or friend from a bored or nervous passenger
into a useful, interested, and relaxed crew member, even if they don’t know how
to fly.
Unless we have some form of autopilot, a copilot during serious instrument
flight in a very busy ATC environment is arguably a necessity—not required by
regulation, but without a doubt, hand-flying instruments without a copilot is a
very tough job. Flying a light aircraft in serious weather, on instruments and
alone, is much more difficult than flying an airliner with a crew. When smaller
jets were approved for single-pilot operation, an operational autopilot and boom
microphone, among other things, were required equipment. This is a smart choice
with any aircraft, automated or not, as is the requirement to advising ATC if the
autopilot or other technology we require has failed. Then we can decide if that
day’s weather and ATC environment is workable for us, diverting if not.
An Extra Hand
Without a helper, the workload gets pretty heavy. One way to reduce it is by using
a boom mike. The wide use of intercoms and headsets, especially noise-reducing
headsets on many general aviation aircraft, has automatically brought the boom
mike into wide use—a fine advance. In the past, fumbling around to find the
mike, getting it off the hook, holding it up and pushing the button, taking one
hand out of use was all terribly primitive. With a boom mike and a button on the
control wheel, one need only squeeze a finger to communicate. The other hand is
free to write messages, adjust gadgets, fiddle with buttons and knobs on high-tech
avionics, and do the many chores it may be called upon to do.
Navigation
GPS is certainly the wave of the future, even with the times folks must use VORs,
and the few ADFs that remain. It’s wise to remember, however, that all the good
of GPS and advanced electronic navigation bring with them programming. While
this interface is getting better all the time, as of this writing we still must respect
that when one deals with this, added effort is necessary to be certain, by care and
double-checking, that it has been programmed correctly. Serious errors have
occurred because of programming errors, whether in new aircraft or more so our
day-to-day programming of electronic navigation systems. This also applies to
older, stand-alone navigation systems like non-FMS Inertial Reference Systems
(IRS ) and GPS units.
Also, remember that low-frequency aids, such as the mostly discontinued
LORAN, (which in some ways was unfortunate), or even the good old ADF, can
be subject to precipitation static in heavy snow, some rain, and in thunderstorms.
The best defense is to be certain the installation is properly done and the airplane
has been rigged with antistatic antenna, discharge wicks, and such to minimize
“P” static, as it’s called. And realize that there may be occasional but infrequent
periods of no reception because of static, regardless of the aircraft’s equipment.
The new aids do such a remarkable job that we’re apt to expect them to do
everything, but they do have limitations, and one should study the manuals, learn
the equipment, and be certain to fly within their limitations and our own common
sense.
Today’s modern navigation aids have made this task easy. They also have a
tendency to lull us into a euphoric state of thinking everything is fine.
Unfortunately, we hear too many cases of people crashing into mountains, not
knowing where they were and unaware of possible flight path dangers. As we said
before, it is still the pilot’s responsibility to know where the airplane is, what kind
of terrain it’s over, and the terrain’s height. Maps remain an important part of the
cockpit gear; we have not reached the state where electronic gadgetry can be
trusted 100 percent of the time. The picture of a pilot flying on autopilot, being
guided by GPS and sitting back reading the newspaper or fiddling with nonflying
related issues, is a shocking one. Flying an aircraft should be a 100 percent job.
Giving it any less attention is reckless.
Radar and Lightning Detection Systems
With all the computerized weather information of today, it’s pretty loose to
consider flirting with thunderstorms without either NEXRAD, airborne radar,
and/or lightning detection equipment. We get into this later, in Chapter 15 on
thunderstorms.
9
Temperature, an Important Part of
Weather Flying
Temperature is closely related to many things we do with airplanes. It affects
performance in takeoff, climb, cruise, and landing. It’s important.
Air is the thing we use to make our airplane fly. How much or how little of the
air that is available to our airplane relates to the number of molecules. The amount
of air striking the wing is a function of speed and of the number of air molecules
present. If cold, the molecules are packed closely together, and we say the air is
dense. If it’s hot, there are fewer molecules per cubic foot, and the air is less
dense. We sometimes say it’s “thin.”
If the air is more dense, the better our peak performance. In dense air, engines
put out more power; the wing has more lift. When the air gets hot and thin, it’s all
reversed, and performance suffers.
Temperature and Density
There’s another way of looking at it. At sea level, the air has a certain density, but
at altitude, the density is less. We know how this affects performance. When we
take off and start climbing, our rate of climb is, say, 1,000 feet per minute. As we
climb, the rate decreases until reaching the airplane’s absolute ceiling, where there
isn’t any rate of climb.
Why did the airplane stop climbing? It’s simple: it ran out of air. The air
wasn’t dense enough to feed the engine, and keep its power, so it couldn’t push or
pull the wings fast enough to fly in the high and/or hot, less dense air. The
airplane’s performance is limited by thrust, or lack of it. If there isn’t enough push
or pull, the airplane stops climbing. An unwary pilot may keep pulling the nose
up, trying to eke out a higher altitude or stay at a marginal one and get to an angle
of attack pretty near stall—and that’s a fragile situation! So without air, an engine
doesn’t do its job, wings don’t lift, and humans don’t live.
This happens as we climb, because the air is less and less dense at higher and
higher altitudes—not because of heat or cold, but because the atmospheric
pressure is lower. The higher we climb, the less air there is above us pushing
down and creating pressure. It’s always impressive to realize that half of the
atmosphere is within the first 18,000 feet of altitude! At sea level, the atmospheric
pressure is about 30 inches of mercury. At 18,000 feet, it’s about 15 inches of
mercury.
Since hot air is less dense than cold air, hot air acts like air at high altitude,
and cold air acts like air at lower altitude. What we’ve said is that air density and
effective altitude are related. A sea-level airport on a hot day isn’t at sea level as
far as our airplane’s performance is concerned. How high sea level can effectively
become is sometimes a surprise.
A sea-level airport on a day in summer, when the temperature is 38 degrees C
(101 degrees F), has a density altitude of 3,000 feet! The sea-level performance of
the airplane will have deteriorated about 20 percent. This figure will vary,
especially with supercharged or turbocharged engines. In any case the airplane
must not be overloaded; it must be flown carefully, and there must be enough
runway for safe operation.
We Better Figure It Out
We can easily figure density altitude on any good computer, whether it be an
electronic one or a good old manual—and elegantly reliable—“whiz-wheel,” with
a density–altitude computation. Density altitude is also broadcast on ASOS and
AWOS. It’s worth a winter’s evening to tweak a computer and run out some
make-believe situations, seeing how density altitudes can vary.
Airplane manuals show performance at different altitudes, from takeoff
through landing. Sometimes we’ll have to figure performance on tricky “chase
charts,” which we’ll need to practice until they become second nature. The
density altitudes we find on the computer can be compared with the airplane’s
performance at that altitude to see what performance we can safely expect on hot
summer days. In the computations, we must consider load—how heavy we are—
and the advisability of reducing load by removing that camping equipment,
“stuff” purchased, baggage, even a passenger or two. The airplane manual will
show the performance versus load, temperature, altitude, and the lot. It’s important
to study and refer to it carefully. Grasping the control wheel with an upward pull,
sitting forward on the edge of the seat, dry of mouth and wishing the thing would
climb and get over those trees is “too-late”; the manual reference should have
come sometime before.
*New nomenclature for millibars is hectopascals (hPa ). However, upper air
charts, etc., still employ millibars. You’ll hear hectopascals with altimeter settings,
etc.
† Note about tropopause: It is where the troposphere meets the stratosphere, which
is also where the troposphere’s cooling with altitude ceases or even warms a bit.
Above the tropopause, in the stratosphere, the temperature remains constant at
−56.5°C, if at standard temperature and altitude as shown in the above table.
There can be variations, because the tropopause height will vary widely.
How Hot, How High?
If one flies out of high-altitude airports, 5,000 feet or more, with hot temperatures,
it’s not unusual to have a density altitude of over 8,000 feet! Some low-powered
airplanes will hardly fly at that altitude, and even the best will have impressively
reduced performance.
Standard temperature at sea level is 15 degrees C (59 degrees F). That’s what
all those manual figures are based on. The moment the temperature has gone one
degree above 15 degrees C, the performance has started to deteriorate. Remember
that on a warm summer day when taking off from a small country airport with
trees to clear at the end of the runway!
Only 10 degrees F, or a couple of degrees C, above standard can make an
impressive difference, and if the wind is light, or almost calm, don’t shrug it off as
unimportant then take off on any convenient runway. Be sure, after takeoff, that
you will be climbing into a gradient wind that will be on your nose helping
performance, not into a tailwind and its sagging shear affect. Avoid the doublejeopardy situation of poor performance from above-standard temperature and
soggy airspeed struggling through shear. It is important to consider the lay of the
land for the airport. If the wind is calm, or nearly so, with no wind shifts or
gradient issues, taking off downhill and/or over low or no obstacles deserves
serious consideration. Conversely, landing with similar wind situations, doing so
uphill when length is tight, is also an important consideration.
Engines Don’t Like It Hot
Heat affects the engine’s running, too—piston or jet. It doesn’t put out as much
power, because it is flying, in effect, at a “higher” altitude.
Running a piston engine on the ground can excessively heat up heads and
other engine parts. Tightly cowled engines need a lot of cooling airflow, and when
we are sitting on the ground in hot weather, the engine isn’t getting the flow it
may need. We should keep ground-running to a minimum, and if we must sit there
with the engine running, be certain our nose is headed into the wind to gather all
the air possible.
Engine vapor locks can occur quite easily in hot weather, but most modern
engine systems are designed to prevent these issues. However, if fuel boost pumps
are required to be on for takeoff, it’s worse to forget them on hot days, when
vapor locks could occur. If we use that checklist, this will not be a problem.
All this suggests that cold days are wonderful. They are, for airplane and
engine performance. The airplane leaps off the ground and it climbs like a
homesick angel; it’s one compensation for shivering in a cold-soaked cockpit.
One of cold weather’s hazards in relation to air density is its effect on the
altimeter. In very cold air, the altimeter will read higher than the airplane’s actual
altitude.
For example, flying at 10,000 feet with a temperature of minus 32 degrees C
(minus 25 degrees F), which is 27 degrees C (49 degrees F) below standard, if the
altimeter setting was furnished by a sea-level station, the altimeter will say 10,000
feet, but our actual altitude will only be 9,000 feet! So if we were poking around
mountains counting on 1,000-foot clearance, we might not have it.
Imagine a low approach to a sea-level airport with a very substandard
temperature of minus 26 degrees C (minus 15 degrees F), such as one can get in
colder climates, or more insidious, an unusually cold winter in a place where folks
normally are not familiar with these problems. When our altimeter says 300 feet,
we’d only be at 258 feet . It’s seemingly not a big difference, but big enough
when you’re making an approach to a 300-foot-minimum airport. If we are
established on a 3.00° glideslope angle, at 70 knots (ground speed) for a singleengine aircraft, we’re losing about 6 feet per second. That’s not a lot of time to
delay decisions. (A light twin is around 10 feet per second and a jet about 12 feet
per second.) A good rule to remember is that for every 11 degrees C (20 degrees
F) the temperature varies from standard, there is a 4 percent lower error in the
altitude compared with that indicated on the altimeter (lower temperature, lower
altitude).
So cold temperatures are fun to fly in, but they can give us erroneous altitude
information, which can be disastrous. What this all says is that temperature, like
wind, is one of the elements that a good pilot must become aware of, constantly
checking what the current temperature is and how it’s going to affect the flight.
10
Some Psychology of Weather Flying
Before getting into weather flying, we should talk about emotions. Basically,
airplanes get us into places and situations that humans weren’t designed for. The
inside of a thunderstorm, for example, where the airplane is battered by
turbulence, where there are deafening, rapid-fire staccato noises caused by heavy
rain, and sometimes hail beating on the airplane and our nerves. Lightning
flashes, thunder is heard, and now and then a flash of lightning leaves an odor like
the burning insulation of an electric wire that spooks our inner senses.
In clouds, with ice collecting on the airplane and a very low ceiling at our
destination, we can feel pretty lonely. With a little imagination, a pilot may
wonder if that cozy world is still down there at all.
At times, flying weather requires a firm grip on one’s emotions. Emotions
have to be subdued by realizing that to lick weather, one needs logical, step-bystep thinking and intelligent use of equipment. Wishing will not make a successful
descent through the clouds and landing at the airport. A good job of flying will.
Sometimes a pilot’s firm grip on emotions means forcing oneself to control a
nervous stomach, dry mouth and shaking hand. It might be fighting to overcome
staring at instruments with nothing much registering in our minds; instead we
force a hyper focus to cognizant control of the aircraft, and then work back out
into the broader range of managing the flight. It’s like rebooting ourselves without
turning off our brain’s computer. This isn’t always easy, and anyone who says
they’ve never been scared flying in weather either isn’t telling the truth or hasn’t
been there!
What we have to do is control any tendency to panic, instead keeping
everything under control. One can be anything from slightly to completely scared
and still think—and think we must.
A difficult factor is that sometimes in flying we can be nervous or scared for a
long period of time. We may sit on instruments a number of hours with everything
under us below landing limits and our destination on the ragged edge as well. This
type of operation is known as “sweating it out,” and never was a more perfect
description thought of for anything.
Self-Discipline
When everything inside us is scared, we have to work harder to do a good precise
job of flying, thinking rationally all the time. In this situation, a pilot must do the
utmost to be relaxed. Being relaxed creates better flying and better thinking,
which reduces fatigue. So even if hell’s fire and brimstone are all around, we must
keep reminding ourselves to sit back comfortably, relax those white knuckles on
the control wheel, and think! It isn’t easy, but it’s possible; and working on it,
forcing oneself, and practicing make it possible. Surprisingly enough, this effort
can develop a control over our emotions that favorably affects the nonflying part
of our lives, from driving automobiles with their dangers to personal problems of
finance or the heart.
There’s a natural tendency for fright to speed things up. If a person is in a jam
in the air, and especially on a VFR flight when we have not heeded sense to stay
out of a weather squeeze, the basic human desire is to be back on terra firma. If
panic takes over, there may follow a desperate, too-fast attempt to get on the
ground almost any way that seems possible. This is dangerous, with a doomful
prognosis. This is when people try to go lower when they should be going higher;
it’s when they try to auger down through a small hole in the clouds below, too low
from the ground. It’s when they wait too late, as the sky lowers and the ground
rises, at last realizing it’s time to land somewhere before hitting the ground;
nevertheless, they try to hasten a landing in a field without looking it over
carefully, nor have they checked for trees, wires, and what have you around it.
What we must do when fright takes over and panic begins to spread is get up
where we are clear of all obstructions. We stay where it’s safe, even in a circle,
and then, in both cases, take time to think the situation through carefully, get
settled down, and after that act calmly and precisely.
We should talk a bit about asking for help, and while it isn’t a part of the
emotions from weather flying it is related to being in trouble. A pilot shouldn’t be
bashful or reluctant to say he or she is in trouble or getting close to it. The radio is
there to aid pilots. There’s plenty of help around, and a good, clear heads-up will
bring it running. Say what’s wrong, where you are, what’s needed most. Use the
frequency currently being used or the emergency frequency, 121.5 MHz. The
calmer one can be while doing this, the easier it will be for someone to help. On
the other side, if we get into imminent trouble, the first thing not to do is talk on
the radio—we think and fly the airplane. Unlike movies, an airplane in a traumatic
state does not switch control from flight controls to the microphone.
It is well to remember that asking for help should be in the category of last
resort and not a crutch used routinely to help fly weather. Proactive weather flying
and communications means calling Flight Watch, the FSS, or maybe talking with
ATC for flight-following and weather input, when they have time. ATC is not
there primarily to get you through thunderstorms or other bad weather. Their job
is traffic separation, and all other services take second place except, of course, in
emergencies. However, emergencies should be emergencies, and not thought of as
“routine” help for ill-planned flights.
There’s another place we need discipline, and that’s when our modern world
of electronic instrumentation and/or autopilots start doing things they shouldn’t,
especially close to the ground. We need the discipline to bring our high-tech brain,
and the unguided missile we’re flying in, back to the basics, either through
expeditious and skillful knowledge of our instrumentation and autopilot, or if that
doesn’t immediately work, through skillful hand-flying. Then, once settled at safe
altitude and attitude, we should methodically bring our automation back into play.
This is repeated in later chapters, and where it may seem we’re over doing this
situation, real-world incidents say we’re not.
Think, for Real
People rarely get into the situations we have been talking about, and weather
flying isn’t a desperate thing at all. One reason people do get into trouble is that
they don’t do enough logical thinking in advance. The preflight analysis of
weather, the decision to go or not, the planning of fuel, and the cold decision of
whether the airplane and pilot are adequate must be done logically and
objectively. Do not take on weather beyond the airplane’s capability. A Cessna
172 cannot fly weather of the magnitude a well-equipped high-performance
single-or twin-engine airplane can, and this continues on up the ladder of aircraft
size and performance. Simply and briefly, we need range, enough power to climb
fast and high in certain conditions, deicing/anti-icing equipment, and radar or at
least lightning detection for thunderstorms, as well as instruments, avionics, and
autopilot to relieve the multiple workloads that weather and the ATC system
demands. With respect to how we think, hunches, assumptions, and “that’s close
enoughs” don’t have much place here—with the exception that negative ones
cannot hurt, such as, “I’ve got a hunch that place will fold up, so I’m going to
take more fuel.” Actually, that probably wasn’t a hunch, but a judgment made
after studying the weather, and experience we’ve gained over time, creating
subconscious sense.
But irrational optimism, like thinking, “It’s going to be okay,” on the basis of
a keen desire to get where one wants to go, is taboo in this business. If a pilot uses
logical thought processes and keeps emotions under control, it will become
possible to handle tough problems with composure. Being prepared with proper
briefing, keeping up with weather’s changes, knowing equipment, and feeling
competent with practiced flying allows one to find that desperate situations
seldom seem to occur.
11
Turbulence and Flying It
Turbulence comes in all sizes, from a little choppiness to big, hard clouts. It
affects us near the ground and up high where jets fly; even U-2s at 70,000 feet
find turbulence. Unfortunately, we cannot see the motions of air, and there is still
doubt about how, exactly, the air moves when it’s disturbed. Flying gliders close to
mountains has taught us much about the interaction between wind and mountains
that creates turbulence, sometimes very nasty turbulence. And working gliders in
these mountainous areas has also taught us about waves, both how to avoid or
benefit from their fascinating action.
Flying over the sea, too, one cannot look down on the endless waves,
whitecaps, and swells without thinking that the ocean below probably isn’t much
different from the one we fly in. They just have different densities. A wave comes
toward the shore and hits a line of rocks. The water sprays and tumbles over the
rocks, creating a confusion of wild water. Make the rocks a mountain and the
water fast-moving air (wind), then the similarity becomes obvious.
Is this much different from wind hitting the trees on the approach end of a
runway, being pushed up then broken apart, descending in a confused manner
toward the ground downwind of the trees? No, we don’t think it is.
Way up at 35,000 feet, couldn’t turbulence be a moving mass of air in waves?
The wave breaks and, if we could see it, might look like an ocean wave, the kind
surfers ride.
All this comparison may be amusing to think about, but how does it help? It
helps in visualization. Our wave breaking over rocks, which would give us a wild
time riding in a boat, can be much like the wind coming against obstructions; it
will be disorganized, so our airplane will roll, yaw, and pitch, as well as balloon
upward, then descend. We must be prepared to combat this.
Some basic—but important—views of wind effects around an airport.
Visualize water rushing down a streambed and then flowing over smooth,
downward-sloping rocks. It follows the contour of the rock bed. A runway
perched up high, with the ground sloping downward, away from the approach
end, is the same thing. Coming in to land, we fly over the sloping area, where the
wind flows down the slope, and we sink as we fly into this downward-flowing air.
A marginally low airspeed, plus aiming to land short, may suddenly find us
touching down before the runway with a good chance of leaving the landing gear
back on the slope as we slide on our belly along the runway.
A good pilot visualizes the air motion around an airport, a mountain, or any
obstruction near the flight path. As we fly by an airport on downwind leg, we
should have in mind the wind direction, velocity, and gustiness. Then, with a
crafty eye, we look at the obstructions and visualize how the air is moving over
them and how it will affect our airplane. We should be prepared for choppy air, a
downdraft, or sometimes an updraft that will make us balloon when we don’t
want to.
Be aware that the wind direction is not always directly down a runway, but
often across it to some degree or other. If obstructions, such as trees or buildings
are to the side of the approach path to the runway, then any cross-component of
the wind will cause spillage over those obstructions, making the approach a
turbulent flight, frequently with strong downdrafts.
Mountains can cause up and downdrafts whose effects can be felt over
considerable distance, and one should look at the terrain for many miles in all
directions and try to visualize its influence. A good example of this was the two of
us (RNB & ROB) taking off from Honolulu in a Cessna 402 for Tarawa in the
Gilbert Islands, 2,400 miles southwest over the Pacific Ocean. It was a ferry
flight, and we were overloaded with extra fuel. Once in the air, after a long takeoff
run, we made a right turn and headed out to sea. Our climb was very poor, but
after flying away from the island, it suddenly increased to the normal rate for the
load we had. Putting it all together, we realized the ground slopes up to about
2,800 feet 6 miles northeast of the Honolulu airport. The pleasant northeast trades
were flowing down the slope of this Koolau Range, causing a large area of
settling air that we were trying to climb in. It kept us down until we flew out of it
8 to 10 miles from the mountains, after an interestingly low tour of the ocean.
Kinds of Turbulence
Turbulence can be categorized according to its location. These are the places and
areas pilots find turbulence:
• near the ground, in those obstructions we talked about or around hilly and
mountainous terrain;
• in the convective layer of the atmosphere or, in simpler words, in the haze
below the inversion;
• in clouds, of course, and the more unstable the cloud, the rougher;
• in clear air at higher altitudes.
The last one, in clear air at higher altitudes, is not to be confused with the
turbulence in the convective level. It is turbulence in clear air well above the
convective level, generally in connection with a jet stream. But there are other
things that may cause it, and we’ll go into them later.
How We Fly Turbulence
We should talk about the ways we fly an airplane in turbulence. Basically, it’s a
matter of not fighting, but rather letting the airplane have its way with the little
displacements it wants to make. We don’t sit there and madly fight the stick or
wheel.
This, of course, has its limits, and there comes a time when we say, “Whoa,
baby, you’ve gone far enough.” Then we move controls and make the airplane
come back where we want it.
Because an airplane pitches, rolls, and yaws, we might look at turbulence
from those aspects. Let’s start with pitch, the up and down movement of the nose.
A gust will make the airplane’s nose change position. What we want to do is keep
the nose where it should be, and that position is the place on the horizon, real or
artificial, for the speed we are trimmed. We fly this attitude and keep the nose near
that point on the horizon.
If we take off, put on power or reduce it, this attitude will change, requiring us
to retrim the aircraft. But these trim changes are small. In clear air on a calm day,
we can see what positions the nose takes for different speeds and different power
settings. What we want to avoid is large displacements of the airplane. One
quickly learns that big power changes make big attitude changes. This is a clue, of
course, that juggling power during turbulence in large amounts will result in big
attitude changes, out of trim control forces, and general confusion in flying. We
don’t want that. It’s best to know the speed one wants, trim for it, and then ride it
out, keeping the nose very near this trimmed position.
On that clear day mentioned above, one should try and memorize pitch
settings, on the artificial horizon, versus power settings and trim for everything,
from best turbulence penetration speed to climb after takeoff. They will vary with
load and altitude, but will be valuable as something to quickly grab when needed
—at least as a starter. This knowledge is also useful in the event of airspeed
indicator failure, iced-up pitot, taped-over static port, or a mechanical failure.
Altitude will vary. If it’s very rough, and you are worried about the structure,
let it vary! Otherwise, make the smallest possible power adjustments and keep the
flying technique as simple as possible.
Roll and yaw are mixed together to different degrees in different airplanes.
Push a rudder pedal and the airplane yaws; as it yaws, it will begin to bank,
sloppily, but it will. In a swept-wing jet, this tendency is very strong. Push the
rudder and immediately it starts to bank, too. Bank the airplane, on the other hand,
without moving the rudder and its nose will eventually start to yaw around.
Another thing that happens with bank is that the nose goes down. Bank the
airplane, and the nose starts down; unbank it, and the nose rises. The important
time, however, is when the nose goes down. That’s how spiral dives begin if a
pilot is on instruments in rough air and is not experienced. The airplane banks,
and the nose wants to go down. If the pilot pulls back without doing anything
about correcting the bank, the bank steepens, the nose drops more, and the speed
goes up. It’s a spiral dive off and running! It happens very fast. Many airplanes in
this condition will, when improperly flown or not corrected, reach redline
airspeed in something like five seconds or less!
So, keep the wings level! It’s simple, really, to keep the wings level and keep
the nose where it should be on the horizon. Do it in a relaxed way with easy
pushes and pulls, not jerks and shoves.
Convective-Layer Turbulence
Now let’s talk about turbulence in the convective layer, the stuff below the haze
level. We’ll say that today’s a day for it. A front passed yesterday, and from our
study window, across the rolling country, the visibility is good in a brisk northwest
wind. There are small, widely scattered cumulus—CU—drifting rather fast across
the sky.
Just a glance at all this says it will be rough from takeoff until we get on top of
the CU—probably only about 5,000 to 6,000 feet, because it’s November, and in
colder weather the tops are lower than in summer.
There are mountains in our country with farms, fields, and woods. As we
takeoff and climb, it will be rough. Turbulence will start pushing us sideways as
soon as we leave the ground, jolting and jarring. That will last until we reach 800
to 1,000 feet, because of the turbulence from the unstable air being joined by the
turbulence of that strongish wind bouncing over the hills, trees, and fields. So
there are two types of turbulence: orographic turbulence caused by terrain, and
instability turbulence within the air mass.
Above 1,000 feet it will still be rough, quite rough, but some of the small,
jiggling, jolting, fox-terrier kind of action will be gone as we get up out of the
orographic influence.
We reach the level of the cumulus, climb up above that, and suddenly, like
flipping a switch, it is smooth. The haze is below us, and at our level, visibility is
truly unlimited. It’s the place to be.
But let’s go back and wallow around in the rough air below. How rough it is
depends on the air’s instability and is the strength of the wind. The fresher the air
mass (that is, the first day or two behind a front), the stronger the turbulence. The
air is colder than the ground, which heats it and sends the air upward in fastclimbing thermals. These are the days glider pilots become giddy. The sky is full
of lift, and they make records and go long distances.
But in an airplane, each thermal we go through is a bump. Some of them are
pretty strong bumps. Out West it’s not uncommon to fly a glider in thermals going
up more than 1,200 feet per minute. Hit that column of rising air at airplane
cruising speed, and it’s a good jolt. With well developed, wider thermals, bumps
become surges, at times requiring us to pull the power back as we work to keep
the airplane level and our speed approaches limits. Conversely, coming out of the
thermal, there is sink and the process reverses.
If we don’t mind pounding around below the cumulus, we can save fuel and
maybe increase the cruise speed by picking a path under cumulus, especially
when they line up in what are called cloud streets. Now we’re flying with that
efficiency a good sailplane pilot knows. Of course, not all days of good thermals
have cumulus, because the air mass is too dry. Then, as we say in soaring, finding
thermals is more like walking through a forest blind-folded; well, not totally,
because we can look at terrain as a catalyst to lift, so we can weave our course a
little, picking potential areas of lift.
This beautiful cumulus-filled sky is a perfect West Texas summer’s soaring sky.
The cumulus form from thermals, which begin having clout later morning and
may not end until the sun is quite low in late day. If the atmosphere is too dry, the
thermals are still there but no cumulus to mark them. Flying through these
conditions we will find turbulent jabs and jolts, transitioning to a dramatic surge
in thermal cores, their lift sometimes over 1000 feet per minute, with similar sink
once out of the thermals; in such conditions, one should consider flying slower
airspeeds for turbulence. In such arid country cloud bases can easily reach
15,000 – 18,000 feet! To find smooth air we fly above these CU, but we’ll need an
airplane with high-altitude performance and oxygen or pressurization. The other
trick is to fly early or late in the day. (PAUL BRADY/AOL INC. USED WITH
PERMISSION)
It’s Rougher Than You Think
I’ve often thought, while bouncing along in the convective layer, that if I were on
instruments near a thunderstorm, hitting bumps this hard and certainly no
stronger, I’d be quite concerned. We’d have the airplane slowed down and be
using our best turbulence flying technique. But because it’s clear and sunny, we
don’t think much about it. Sometimes we should, because the airplane’s structure
is taking a beating.
A special time to consider this turbulence is during descent. We often see
pilots push the nose down for descent, letting the airspeed increase until the
airspeed needle is tickling the red line. This usually starts above the turbulence,
where it’s smooth, and the airplane is making impressive time. Then they descend
through the inversion into the convective layer and suddenly it’s like hitting a
brick wall, with really solid bumps. The combination of very high speed and the
strong jolts are certainly putting a heavy load on the structure.
An alert pilot will reduce airspeed before whamming into the roughness below
the haze level and then, after the intensity has been felt, make decisions as to the
best speed for the descent, considering comfort and the airplane’s structural
integrity. High performance aircraft have turbulence penetration speeds, while
other aircraft, such as lighter general aviation designs, maneuvering speed.
Fly above this kind of cloud. Like the image above, beneath these cumulus it will
be rough and uncomfortable, while on top the air will be clear, smooth, and cool.
In less arid climates we may find tops around 5,000 to 10,000 feet. (NOAA
PHOTO)
There’s little reason to stay down in the convective layer and bounce around if
you can top it. In the East this is generally fairly easy, because the top of the layer
isn’t much over 7,000 in winter and 10,000 in summer. In the far West, as pointed
out in the figure on the previous page, it’s another matter. Because of the high
ground and strong heating from the arid land, the haze level will often be above
15,000 feet. Then you need oxygen or pressurization.
Flying in the constantly bouncing air is fatiguing, and it’s uncomfortable for
passengers. The bouncing kind of wears on the aircraft structure, too. This isn’t a
serious point, unless we really push the old bird, but it is worth considering.
Dust Devils
On windy, rough days, especially in the West, where there is less grass and more
dirt, dust devils form. These look like miniature tornadoes that work across the
countryside, kicking up dust and dirt in a swirling cloud. They are easy to avoid,
and it’s a good idea to do so. On landing, one can get roughed up near the ground,
settle drastically, or flat lose the airplane, hooking a wing as one is tossed around.
The action feels much like prop wash or jet vortex; it has that uncontrollable
feeling. Even after one is on the ground, the dust devil can lift a wing or flip an
airplane over.
Big dust devils are obvious, but smaller ones may only look like gossamer,
funnel-shaped ghosts skittering along. If we aren’t looking carefully, we might fly
into it. These things are not always made of dust; we’ve seen them as clumps of
swirling grass from cut fields, among other things, and one day while flying a
good thermal in a sailplane, these clumps of hay wafted by the canopy at 6,000
feet.
When dust devils are forming, it’s important to have airplanes on the ground
well tied down, again because a dust devil can easily turn over a parked airplane.
Turbulence Near Mountains and Ridges
Flying during strong wind conditions in mountainous areas, as well as ridges,
particularly when the air is unstable, can result in some very rough rides. The
windward side of a these ranges will have predominantly rising air. It will not be
consistent, but rather choppy and gusty. The gustiness will show itself in great
ballooning climbs that will make you feel you’d like to reduce power, followed by
sinking feelings as the lifting air diminishes. Often this variation will simply be
the result of flying from one contour to another. Mountain ranges and ridge lines
are rarely ruler straight. They have cuts, twists, and pockets, so the wind hits the
ridges at different angles. Also, the slope angle will differ which further
complicates matters. All these irregularities create variations in the effect of the
winds over the mountains and ridges. Glider pilots who have done a lot of ridge
soaring learn this, and an experienced one can often look along a ridge and tell
what kind of lift and turbulence will be found and where. However, they also
learn there can be surprises down low that can be quick and dramatic. Sailplane
pilots who know and respect the eastern United States’ Allegheny and adjoining
ridge systems have set records in excess of 1,000 miles. These are dawn to dusk
flights, flying at low level and high speeds, paralleling the ridges in turbulent lift
from strong, northwest winds!
On the downwind side (lee side) of a mountain or ridge line, the air will
mostly be going down. It will be chopped up, spilling, and rough. The place to fly
is well away from the side of the ridge or mountain. In unstable air, ridges and
mountains—especially the upwind and sunny sides—will produce thermals,
which up higher might be rising shafts of air, but down low are often torn and
inconsistent bubbles that add to the confusion of turbulence.
In powered aircraft, we don’t always fly along mountains and ridges, but often
cross them at right angles. Never approach the top of a ridge or mountain at a 90degree angle, make it 45 degrees, then if you’re having trouble getting over the
top, it’s a shorter turn to get back to the valley. When we approach a ridge, it’s
important to be aware of the wind. We’d like to know whether it’s a tailwind or a
headwind, which varies closing speed, and of course how will it hit the ridge,
creating rising or sinking air.
Say we are flying low, 500 feet or so, above the ridge tops. With a tailwind,
the airplane will theoretically climb as we approach each ridge. We are being
“zoomed” by the air flowing up the slope. But when we pass the ridge and fly to
the downwind side, the airplane will sink, and we’d better be prepared for it.
Flying the other way, toward ridges into a headwind, has the opposite effect
and is hazardous, because on approaching the ridge or mountain, we enter its
downwind side. We could also call this the downslope side. We will sink, often
below the mountaintop, and need power to keep us from getting too low and too
slow. We shouldn’t just pull the nose up and let airspeed drop while trying to
climb. Use lots of power and get up, but it’s usually best to turn away from the
condition with sufficient airspeed and bank angle—control—running to the valley
where we came from and reevaluate the situation. However, it is best never to fly
low near mountains, especially the downwind side, particularly if the wind is
strong. Again, we should be particularly careful flying toward them into a
headwind, because of that sinking problem, which can put us in a dangerous
position. Speaking specifically of mountains and larger ridge lines, never
approach a mountain ridge from the downwind side, except with lots of altitude: a
good recommendation is to use half the height of the mountain you’re crossing,
with 2,000 feet above the ridge or mountain a minimum. If it’s a big mountain
and the wind is strong, this is a good start, but sometimes it’s just not the place to
be, and finding a different route or maybe not going at all is the solution.
A hazardous place to fly is between two ridges so closely spaced that
downward-flowing air from one ridge is turning to climb up the next ridge. The
air movements will be confused, and there will be lots of sink. The other issue
here is that airflow over the top of the first ridge may strike the upwind side of the
next ridge downwind, creating sinking air where you expect lift. Those are real
micro-terrains and micro-weather issues, best heeded cautiously and left to those
who are local and well experienced. Things can also get really strange when wind
strikes a knoll or lone peak, the downwind side can be chaotic when split airflow
rejoins.
When flying along or across a mountain range, realize that the wind speed will
increase where cuts and passes go through the range, because of venturi-like
action, and the turbulence will become worse.
The wind speed over the top of a mountain increases in much the same way
that airflow increases over the curve of a wing. In the extreme, many of us have
heard of Mount Washington in New Hampshire recording winds over 200 mph! It
wasn’t the general wind going that fast, but rather the wind accelerated by the
curve of the mountaintop. Almost any mountain will have this effect to some
degree. Where the wind speed increases, there will be shear and turbulence on the
top and the downwind side.
Of course, what all this means is that we shouldn’t fly close to mountains
when the wind is strong and the air unstable, especially on the downwind side. If
you are close to a ridge or a mountain, never, never make a turn toward it. Always
turn away. To really respect and learn about flying in mountains, we strongly
recommend ridge and mountain flying in a glider, taking a mountain flying
course, or at least perusing some writings on the subject…and the sailplane flying
is fun, too.
Mountain Waves
Mountains create another type of turbulence that extends above the convection
level; it’s connected with mountain waves, sometimes called lee waves or
standing waves .
Fast-moving air—stronger winds in an air mass with a lower stable layer—
hitting the side of a mountain causes waves in the air downstream of the
mountain. They are like waves in a river behind a submerged rock. Waves in the
sky sometimes extend to great heights. The front side of the wave is going up, and
glider pilots like to hunt for this area and make altitude flights. The world altitude
record in a glider, at this writing, is 50,721 feet off the Andes in Argentina, in a
two-place sailplane flown by Steve Fossett and Einar Enevoldson. In the United
States, it is 49,009 feet by Bob Harris, off the southern half of the Sierra Nevada
Mountains in California. From the 4,000-foot Green Mountains in Vermont, the
state record exceeds 27,000 feet, and to the east over the White Mountains of New
Hampshire, folks have exceeded 30,000 feet. We’ve felt wave influence at 7,500
feet from a 700-foot hill in eastern Pennsylvania, and admired world record
distance flights from high-speed cruising parallel to mountain waves.
Just about any ridge or mountain area will, with the right conditions, have
waves that affect our flying. Even over the North Atlantic Ocean, on the east side
of Greenland, with the correct air mass and wind conditions downwind from that
island’s tall mountains, airliners have experienced severe turbulence from waves
off the mountains on that dramatic land.
Let’s visualize these waves. They form downwind from the mountain, not
very far from, in fact almost over, the peak of the mountain. The waves repeat
downwind with second, third, and fourth waves, and often lots more. The waves
go up on one side and down on the other. We often discover them by noticing the
airplane wanting to go up, then as we push the nose down to hold altitude, our
airspeed increases without our adding power. We are in the up part of a wave. The
air is generally glassy smooth.
On the other side we get a smooth downflow. We have to pull the nose up and
add power to hold altitude. This area is smooth, too, and maybe we feel a little
choppiness transitioning between the lift and sink areas. So far, so good.
However, under the wave, we find turbulence in an area called the rotor, where
the wave air conflicts with the undisturbed normal air below and causes a
tumbling, rolling, chopped-up, confused mess. It is rough, and how rough depends
on the strength of the wind, the mountain, and how much of a wave there is. It can
be very rough! In severe cases, this rotor has torn an airplane apart. It’s not a thing
to fool with.
This shows two types of mountain turbulence: one is the tumbling air in the lee of
a mountain; the second is the rotor under a wave. The little cumulus on top of the
rotor, a small shredded wisp-like cloud forming, is the cue telling where the air is
very rough. The two types of turbulence can occur at the same time or separately
when there is no wave action but lots of wind spilling over a mountain.
How do we know it’s there? First, with strong wind flow across a mountain,
especially after a front has passed, we can expect wave action. Looking up into
the sky, we may see lenticular clouds. These are a characteristic sign of waves.
They are long, slim, lens-shaped clouds, but the real key is that they do not move
as normal clouds do. The reason for this is that the rising side of the wave cools
air to its condensation temperature and forms the cloud. As the air starts down the
backside of the wave, the pressure increases, the air gets warmer, and the cloud
disappears. Because the mountain doesn’t move, neither does the wave and its
lenticulars, except for minor variations due to atmospheric conditions. So the
lenticular cloud forms and disappears on the wave, staying with it and not drifting
along with the wind. If near the level of the mountaintops, it is very turbulent
under lenticulars, or where they would be if the atmosphere is too dry for the
lenticulars to form. When there is not enough moisture to form a lenticular cloud
the wave is there, lurking invisibly. We should not be lulled into thinking there is
no wave because there are no lenticulars! Any time the wind direction is across a
mountain range or within an arc of about 70 degrees of perpendicular, the wind
maintains this direction with height, and the velocity increases with height, you
should be suspicious of wave action.
In the valleys downwind of the mountains, the rotor often extends almost to
the ground; the air near the ground is rough, and one can see clouds of dust
swirling into the sky, if it’s a dry, dusty area. We’ve seen rotor off the seemingly
gentle Green Mountains of Vermont that was almost down to the runway of our
local airport. Descending to land, all the way through the landing pattern, was
wildly turbulent. In more extremely mountainous areas, when it’s very windy it
may be best to stay on the ground or avoid the area.
Flying downwind of mountains, we want to be especially careful when the
possibility of a wave exists. Sometimes we can get the combination of air-mass
instability and wave-rotor action together, and it makes for a mighty interesting
ride!
Rotors can lie fairly high in the wave structure, but the most turbulent rotor
will be found at the mountain level and below. If the mountain is 4,000 feet high,
then the rotor will potentially be roughest from 4,000 feet down. To be on the safe
side, we should again add 2,000 feet or so to the mountaintop altitude, in an
attempt to avoid the worst part of the rotor. If you can see the rotor clouds, fly
above them. For bigger mountains, it would be advisable to add extra altitude
above the mountain height, say 5,000 feet more. But the best way is to avoid the
area altogether.
Waves can be created by just about any size of a mountain, but as we’ve
explained, they are not always visible. The rotors, however, will sometimes show
themselves as little pieces of shredded cumulus-like cloud. There may be moisture
in the lower levels that will support, or almost support, small cumulus, while there
is not enough aloft to make a lenticular. So if you see cumulus on the downwind
side of a mountain, generally not much higher than the mountain, and when you
study them carefully you see a shredded, moving, turning-over appearance to the
top side of the cloud, look out! That’s probably a rotor. Sometimes there will only
be a few small, half-formed, gossamer-like wisps of cumulus that you almost
“feel” rather than see, but if we’re watchful and see them, they can tell an
important story. Those innocent-looking wisps may signal a very rough rotor. Any
atmosphere like that downwind of a mountain should be cause for suspicion and,
if one must fly through, it is time to prepare for flight in turbulence.
Any flight downwind of a mountain, even a small ridge only 500 feet high,
can have a nasty rotor if the wind is strong and the air unstable. Flight down low
is not the thing to do. It’s no time or place to be circling a friend’s house or doing
other foolish, low-level flying.
An idealized illustration of a mountain wave system and related atmospheric
aspects. The wave is illustrated on the right, including classic placement of clouds
related to waves that, depending on atmospheric conditions, may or may not form.
Turbulence is also noted. Wave strengths, both of lift and sink, can vary from very
little to thousands of feet per minute, as do variations of wave height, wavelength,
number of downwind harmonics, and rotor turbulence level; these all depend on
terrain height, shape, wind velocity, and atmospheric stability. On the left, we see
the relationship of temperature and dewpoint vs. cloud formation. Note the
atmospheric stability at mountaintop height (temperature no longer decreasing
with altitude). Far left is wind information, indicating similar direction and
increasing velocity with altitude, as advantageous for wave formation.
(COPYRIGHT: METPANEL OSTIV—THE INTERNATIONAL SCIENTIFIC
AND TECHNICAL ORGANIZATION OF SOARING)
Beautiful lenticulars that tell a wave is working in the sky. They are smooth and
peaceful looking, which can be the case, if our aircraft is snuggled in front of a
lenticular’s upwind side, or there may be smooth sink on the downside of the
wave, often more than an aircraft’s climb rate. However, getting to and from
smooth areas usually means passing through significant turbulence, the worst
being in the rotor below the wave system. Below the lenticulars pictured, we see
innocent wisps of cumulus, but such is an indication of rotor turbulence and a
rough ride. Depending on the wave system’s severity, this turbulence can threaten
aircraft control, or worse, cause structural failure. (PHOTO BY ANDREW
LAWRENCE)
When getting in the lift of a wave, the air is smooth and might fool a pilot
flying an aircraft with low power and no oxygen. It’s possible, but not likely if
you are alert, to go up at a fierce rate to a high altitude where oxygen is needed.
The way out of such lift is to turn downwind. But the aircraft would then get in
the down part of the wave, which is also generally smooth. The descent rates may
be high, more than one could overcome with the engine. Pulling the nose up and
pouring on power is not the way to fight the downflow because it’s a sucker setup
to get into mushing, stalled flight and not gain anything in the fight to combat the
severe downflow. It would be best to keep up speed and fly fast downwind to get
out of the wave condition. You might be going down fast while doing this, but the
combination of airplane high speed and the tailwind will get you out of the down
current of air quickly. The pilot might go through a number of waves in the
downwind dash, but that’s the fastest way possible.
Waves do not have a very long wavelength in miles of distance, so it’s easy to
turn and get out of the down and fly into the up part. With our 4,000-foot
mountains here in Vermont, the wavelength is seldom over a few miles wide. It
would be more for larger mountains, but still not a big distance. However, if there
is strong wind at our altitude, the upwind push could take longer than we’d like. If
you’re on a flight plan when encountering the down part of a wave and have
trouble holding altitude, tell ATC the problem and that you’re turning around or
can’t hold altitude. With marginal performance, never try to outclimb a wave’s
downside by, as mentioned a bit ago, pulling the nose up with consequent speed
loss; stall is never far away, unless the aircraft has enough power to climb and
maintain good airspeed.
This iconic photo was taken by Sierra Nevada Mountain Wave pioneer Robert
Symons in the early 1950s, looking south over the Owens Valley, on the east side
of California’s Sierra Nevada Mountains near Bishop, California. It is over
similar location to Gordon Boettger’s picture later in chapter, allowing a look at
the diversity of sky such conditions can produce. With the wind from the west
(right to left), the clear air immediately east of the Sierra Nevadas is a significant
downdraft through which even the most powerful aircraft would have issues and a
wild ride. The dust (and smoke of local fires) is rising to the east (left) on
combined rotor action lifting into strong wave lift; the region below the lower
rotor clouds would be extremely turbulent. Worth noting is that this picture was
taken from a WW II–era Lockheed P-38 twin-engine fighter, with both engines
shut down, as Symons soared the P-38 to conserve fuel and wait for the surface
winds to abate. This also may have been the day Symons made his famous soaring
flight to 30,000 feet in the P-38, again with both engines shut down. In these types
of conditions, pilots should avoid the entire area. (PHOTO BY ROBERT
SYMONS AND COURTESY OF NATIONAL SOARING MUSEUM)
A special situation is a single mountain that sticks up alone, like Mount
Rainier in Washington State or Mount Fuji in Japan. Under strong wind
conditions, the downwind side can have a combination of wave and vortex. The
air spills over the top and around the sides, setting up a great whirlpool action
downwind of the mountain that has severe turbulence. A Boeing 707 was torn
apart in this condition near Mount Fuji. So it’s well to be very wary downwind of
peaks that stand alone enough to create this situation; go around or pass any lone
peak on the upwind side.
Mountain waves are interesting, and playing with them in a sailplane is not
only fascinating, but a good education for the airplane pilot. I’ve (RNB) landed
many times in Milan, Italy, which is snuggled against the southern side of the
Alps. Because of glider experience I was wave-conscious, studying and learning
which conditions made the biggest waves in the area; generally, a quick look at
the winds-aloft pattern told me if I had to be extra careful while descending into
Milan, because of the possibility of wave penetration. Incidentally, the strongest
waves there came with southwest winds from the direction of the French Alps.
The point is that whether it’s Milan, the Rocky Mountains around Denver,
Colorado, a little airport in Vermont, or countless other places, understanding
terrain and wind can give us suspicion, if not a direct warning, that there is
potential wave and all that comes with it.
Photo taken at about 11,000 feet, looking south, over Vermont’s Green Mountains.
Wind right to left. Lenticulars above right are the primary wave, with the
secondary to the left, and further cycles downwind off the picture. Below,
stratocumulus is nearly overcast, but openings reflect airflow of each wave cycle’s
downwind side, causing cloud dissipation, then reforms on the upward flow of the
next wave cycle. These clouds can be at mountain height and are turbulent from
rotor action—not a safe hole to “sneak” through. With enough moisture, it
becomes totally overcast, causing us to be “trapped on top,” unless IFR capable.
(PHOTO BY ROBERT O. BUCK)
Wave action is something we can use to our advantage on cross-country
flights if we’re paralleling mountain ranges, on top, when conditions are right. We
feel periods of descending air, and our airspeed drops way off as we try to
maintain attitude, then at other times, we seem to get a great boost and an increase
in speed way over normal cruise. What happens is we’re flying in and out of
waves, perhaps only mild ones. If we watch the top of the clouds, we’ll see
undulations like swells on an ocean. Eyeballing these, we try to stay on the
upwind side of a “swell,” where we’ll be in rising air and going fast. Moving our
course around to fit these upflow areas may well be worth small detours and, as
we said, the wavelengths aren’t very large in miles, so “fishing” upwind or
downwind may quickly get you out of sinking air into lifting air and an airspeed
boost. At times we may feel this condition in clear air when we cannot “see” the
waves. If so, do that “fishing” by cutting up-or downwind at subtle angle to find
“up” air. A great picture of this beautiful, high altitude world from a sailplane is
seen in the figure on the next page.
A single peak has lots of disturbed air downwind caused by vortex around both
sides and wave action over the top. A sign of vortex is an isolated oval or round
lone lenticular downwind of the peak. If there wasn’t enough moisture to form a
cloud, this condition would not be visible and one might fly into it unexpectedly.
Lesson: stay away from downwind of lone peaks by many miles, going around the
peak’s upwind side when winds are stronger than light.
A unique photo of difficult resolution; nevertheless an important story. Taken from
about 35,000 feet, we’re over Greenland, looking down on a stratus deck of
clouds. The white dots left, center, and lower right are higher snow-covered
mountain peaks that have popped through the strato-cu deck of clouds. Wind from
left to right, behind the peaks we see turbulence churning up the stratus clouds. At
the same time, a wake spreads out on either side of the vortex center, very possibly
causing the rippled wave-like undulations in the stratus. This shows the issues of
vortex turbulence described in the text. (PHOTO BY ROBERT O. BUCK)
One day, when heading to Atlanta, Georgia from the Northeast, somewhere
above 30,000 feet and nearing the Great Smoky Mountains, we popped out of
what we thought was a deck of cirrus, quickly realizing it was a long, long
lenticular, unusually high for waves in that neck of the woods. We felt a kind of
gentle surge and soon reduced the power as our Mach built up. We settled at about
Mach .84, and about 20 percent less fuel flow than normal. In a bit, we began to
slow and felt a tiny bit of light choppiness. Telling ATC we wanted to head a little
right off course, this put us upwind, back into the wave, as we would fly in a
sailplane. Speed (Mach) picked up again, and we wandered on in lift for about 20
minutes, until south of Asheville, North Carolina, when ATC asked: “Hey, where
you going, anyway?” The fun was over, and we turned back to the arrival route.
Arriving in Atlanta, we had beaten time and fuel of the flightplane by a small but
enjoyable bit. So, you can soar a 727—sort of.
So this awareness of the air’s motion may save both fuel and time. It’s the
stuff glider pilots work with and offers an exciting new concept and knowledge of
the sky. It can also signify conditions to stay away from, depending on severity of
conditions, both from wind, atmospheric stability and terrain considerations.
Lenticular clouds from above. Taken over the Owens Valley, east of the Sierra
Nevada Mountains (lower left), looking north near over Lone Pine, California.
Taken by soaring record pilot Gordon Boettger, the altitude is 26,000 feet, heading
northwest (right to left) in a Glasflugel Kestrel sailplane. A very significant photo
—Mr. Boettger is on the last portion of a multiple-leg, 1,400-mile U.S. national
record flight, on May 31, 2011; the longest recorded sailplane flight in the
northern hemisphere. With the wind from the left, or west, the smooth, strong high
altitude lift lies on the upwind side of the lenticulars pictured, allowing highspeed running north and south along the wave. Commensurate sinking air is on
the downwind side of the lenticulars. Below the clouds was extreme rotor
turbulence and very high surface winds. Beautiful, yes, but not the place for most
of us; instead, just a handful of highly experienced and locally familiar pilots.
(PHOTO BY GORDON BOETTGER)
Turbulence Up High
Sometimes turbulence that is not Clear Air Turbulence (CAT) is felt well above
the convective layer, at 12,000 feet and up. This is generally light and associated
with overrunning warm air preceding a warm front. It may also be there because
of other air-mass changes. Often a look up will show altocumulus clouds.
Big, High-Altitude Turbulence
This sort of turbulence obviously relates to high altitude and high performance
aircraft. Maybe a distant subject for the general aviation pilot grinding along way
down low, but it still relates to the idea that all aircraft have performance limits.
Also, with the increase of owner flown turboprops and jet aircraft, this realm is no
longer just the world of professional aviation. We also give thought to more high
performance, turbo-charged piston aircraft, with many sporting higher wing
loadings and more sensitive aerodynamics towards better performance, to which
high altitude flight can have an effect.
So let’s talk about this CAT business—Clear Air Turbulence. This type of
turbulence has been a bogeyman in high flying for some time; it’s been popular in
the press and is often called the “airman’s enemy,” which it isn’t, but it does bear
watching. Let’s look it over calmly.
Most clear air turbulence is associated with the jet stream. The jet stream is a
hose-like band of high-speed wind at high levels. It is one manifestation of
constant movement in the atmosphere as the unequal temperatures of the earth—
hot tropics and cold arctic—try to balance, with warm air working north and cold
air south. There are also fronts high aloft that are part of this process. That is
where jet streams wander, squeezed tight under the tropopause, with high winds
and turbulence that influence flight, as well as the movement of surface weather.
Because the temperature balance isn’t regular and neat, the jet stream doesn’t
string out exactly east and west very often. Generally, it wanders in a serpentine
fashion, so if we fly east or west, we may cross it a number of times.
The jet stream is usually up in the high latitudes in summer, 60 degrees or so,
and down south as far as 20 degrees in winter, but just to be difficult, it wanders
north and south during both seasons. The hose-like part is the area of maximum
winds that sometimes blow at 200 knots. There are also strong winds for hundreds
of miles to the side of this special high-speed jet. The high-speed winds spread
over a wider area to the right of the jet stream, looking downwind and in relation
to the jet stream’s direction, than they do to the left.
Where these high-speed winds rub against lower-speed winds, there is
tumbling, turbulent air. Where air-mass densities change, as in a high-level front,
it’s rough. Where a jet stream slams into slower-moving air ahead of it, it’s
turbulent, too.
Meteorologists can locate the jet stream rather accurately, but pinpointing
exactly where the turbulence will be has always been quite a challenge. They can
tell you where turbulence will be in general terms, and turbulence forecasting is
getting better, especially with today’s uplink–downlink systems in transport
aircraft that constantly send wind, temperature, location, and turbulence data,
among other things. After the two of us (RNB and ROB) have spent over 20,000
hours above 30,000 feet, we can be assured that sometimes it will be rough when
they say it won’t and smooth when they say it’ll be rough.
How rough is it? Moderate at times, perhaps severe by some people’s
standards. Most of the time, the danger of the turbulence itself—CAT—is severe.
It’s uncomfortable, at times very disturbing, and has hurt people in the aircraft
that did not heed wearing a seatbelt. This brings up one of the toughest decisions
of a pilot in command with an airplane carrying passengers—the seat belt sign.
However, despite the trauma and discomfort, the aircraft comes through, so most
of the time it isn’t anything that can’t be handled.
It is possible, however, to get into trouble because of control problems. Up
very high, the airplane has low thrust; it’s mushing along at a higher-than-normal
angle of attack. It’s squirrely, as the expression goes, because its Dutch roll
tendencies become more pronounced, then add some turbulence and it further
antagonizes the process. “Dutch roll” is a coupled lateral (rolling) and yawing
back-and-forth tendency of an aircraft; kind of a corkscrew fashion. It’s most
pronounced with swept-wing aircraft, and especially those of earlier design, but is
much improved in modern swept-wing designs; much due to better aerodynamics,
less wing sweep and augmented flight controls.
What helps stabilize a Dutch roll is a yaw damper, which makes automatic
yaw (rudder) inputs to counteract the tendency. In some earlier jet designs, once
above about 25,000 feet, a yaw damper was required, the aircraft possibly
becoming uncontrollable with the yaw damper inoperative; hence, dual yaw
dampers in some older jet aircraft. The industry has also realized yaw dampers
make just about any aircraft’s stability better, which, as mentioned in previous
chapter, is why we see this augmentation offered on even single-engine piston
aircraft. The yaw damper is, in a small way, an early fly-by-wire concept in which
electronic gadgetry makes flying easier. This is all part of the trend of these
augmentations doing great things, making airplanes fly better than we can, allow
more performance in design and they’ll be more in the future! But, we’ll still have
to know how to fly because being electro-mechanical, these things can fail.
In upper air turbulence, almost all of which is caused by shear, in extreme
conditions airplanes can approach stall and may want to fall off on a wing. Where
most aircraft flying such altitudes and conditions are on autopilots, the CAT has to
be pretty wild to compromise autopilot operation. Never the less, in extreme
situations older autopilot/aircraft combinations may begin excessive pitch
excursions while trying to hold altitude, so we may benefit from disconnecting,
and definitely any airspeed-hold mode, of the autopilot. Then, let the altitude float
a bit (and of course advising ATC of this condition) in trade for constant pitch
control. However, hand-flying the airplane at high altitude—which is admittedly
rare—takes careful flying to keep level and under control, especially in pitch,
where a one-degree change can take us from level to hundreds of feet per minute
climb or descent. Also, if one is flying an aircraft with both autopilot and
autothrottles in excessive turbulence, disconnecting the autothrottle system
prevents the surges, and pitch changes especially problematic with wing mounted
engines, as the throttles/thrust levers chase airspeed. Usually these systems have
better autopilots, which we can leave in full operation, the auto throttles being a
separate entity. These considerations are especially valid at higher altitudes as the
aircraft approaches stall or high Mach issues.
These high altitude concerns are not a desperate situation if the pilot is on top
of it and realizes that it may be necessary to give up some altitude to keep control.
This nervous area is why it is best not to operate above any altitude where the
airplane is close enough to stall, such that a 1.3- or 1.5-G bump might cause the
airplane to exceed the stall angle of attack. In the past, this data was stored in
performance books with graphs and tables relating weight and temperature to the
aircraft’s performance, which we’d reference during flight. Today, with advanced
aircraft, it lives in onboard computers—FMS systems—that read the aircraft and
environmental data and then tell us maximum altitude for our current weight.
Basically, a 1.3-G altitude is good for light turbulence, and anything more is 1.5G, which translates into a lower maximum altitude. If we’re flying higher than
these altitude limits, exceeding turbulence maximums means the aircraft could
exceed the critical angle of attack that threatens normal flight. The only problem
is what really is light, moderate, or more turbulence, again, a pilot’s subjective
decision, often made with only PIREPs from other aircraft as a resource.
When fiddling with high altitudes, we’ve probably heard about the “coffin
corner” where, between a very small envelope of speed—our only indication if
we are without an angle of attack indicator—the aircraft is at either too high an
angle of attack and risks stall or is going too fast, where the wing’s shockwave
slides too far back on the wing, resulting in a kind of high-speed stall, from
aerodynamic issues near the speed of sound. Often one wing is affected before the
other, causing a wing to drop. We also need to remember a turn increases G
loading, which increases the angle of attack, so we need to be gentle in turning at
critical altitudes. Some of the old book data was based on 15° banks on the 1.3-G
chart, which didn’t give much margin. In the early days of jet operation, when less
was understood, such was cause of a few incidents and accidents from mostly stall
excursions. The fortunate events included wild didoes followed by skilled handflying, along with the very rugged designs of those early jets, that saved the day.
We can run into the above issues either by climbing higher than prudent for
the aircraft’s capabilities or cruising in cooler air, then sliding into warmer
tropopause air (we talk about the “trop” in a bit), where one can feel the airplane’s
mushiness. When struggling at these altitudes, the pitch angle is a bit higher, as the
airplane claws for lift in the less dense air. Amazingly, even though this pitch
difference is only a degree or so, an aware pilot can feel this “leaning back.” If the
air gets the least bit choppy, an airplane can begin a slight wallow in that Dutch
roll situation, even with a yaw damper. It’s not comfortable and a lousy place to
be.
Conversely, when you’re experiencing a positive dynamic, such as lifting air,
and the airplane has the desire to “go”—it’s lighter in the seat and kind of like
leaning forward a bit, which is really happening—that pitch attitude now a degree
or so less, but we feel it, too. When flying an airplane with passengers potentially
loose and wandering about, and you suddenly feel that pitch forward, and then a
surge, like a gentle swell in a boat, it’s time to put that seat belt sign on, as usually
in a moment the airplane will enter the staccato choppiness of turbulence. And so
enters the terminology differences between “chop” and “turbulence,” which is
study of criteria in pages of the AIM and other sources. Once in a while, it’s
significant, and you only hope no one gets hurt. These events are not always in an
area where there is warning of turbulence; a good lesson that we can’t fully
predict the sky.
Fortunately, however, modern aircraft and their improved aerodynamics have
reduced quite a bit of these aerodynamically sensitive issues. But again, airplanes
still fly by the same laws, and still have their limits, so the basic concepts should
not be pushed aside as passé. So we heed the formula in flying CAT, which is to
fly the recommended turbulent speeds and procedures, flying as one would in any
turbulence, by attitude, with wings level and pitch and power changes at a
minimum. Doing all these things will make CAT a nuisance and not a disaster.
Where Is It?
Despite the difficulty in forecasting CAT, there are some cues the pilot can watch
for to tell where CAT may be. Before takeoff, the pilot should have a look at a
high-level pressure chart, the 300-mb one, which is about 30,000 feet. Its
wandering isobars will show where the jet stream is apt to be. It’s like any
pressure chart, with the distance between isobars telling how strong the wind is:
the closer the stronger. In studying the wandering curve of the isobars, the pilot
should note especially where the isobars bend and change direction. A trough, for
example, will have the isobars oriented from northwest to southeast on the west
side; then they will turn a corner and orient themselves southwest to northeast
farther east. In the area of the corner, where the wind changes direction, you can
almost count on finding CAT.
Then check the isobar pattern. Let’s say the isobars are all crowded together in
an east–west direction; the wind is moving fast. But farther east, the wind
slackens, and the isobars fan out. It will be rough in the area where the wind
velocity changes and especially if the upper flow diverges. If the velocity changes
faster than 40 knots in 150 miles, it’s a sign there will be considerable rough air.
Jet streams above mountain wave areas have extra turbulence, and the choppy
type found in the rotor will be found at high altitude, but not with the viciousness
of the lower rotor.
There is also wind data telling velocity change with height. Generally, it is
considered that if one sees a wind change of 4 knots or more per 1,000 feet, it will
be a rough area. This we find hard to count on. Sometimes it seems to work, but
we’ve seen occasions where the 4 knots and everything else said it was going to
be rough, only to fly through and never hit a ripple. If this figure coincides with
other turbulence cues, like bends in the isobars, it seems more valid. At any rate,
we watch these areas with suspicion.
The Tropopause and CAT
Perhaps the most interesting thing to study in advance is the height of the
tropopause (trop), which tells us a lot. The tropopause is the place where the
troposphere, in which we live, ends and the stratosphere begins. The tropopause is
a narrow band separating two different kinds of air. The most noticeable
characteristic difference between them is temperature. As we know, the
temperature decreases with altitude in the troposphere and keeps right on doing so
until we reach the tropopause, where the temperature stops getting colder. This,
theoretically, is at about 35,000 feet in the average latitude of the United States.
Above the tropopause, in the stratosphere, the temperature is considered to be
about −56 degrees C, but all this can vary considerably.
To make life more interesting, the trop, as the trade calls it, wavers up and
down with the passage of lows and highs under it, and can actually range in
altitude from the low 20,000s to the 40,000s right over the United States. It also
varies in seasons, usually lower in the cold of winter and higher in summer. The
taught standard says the trop is high over the equator, at about 55,000 feet, and
low near the poles, at about 24,000 feet.
The Tropopause Is Important
A couple of things happen at the tropopause. The temperature goes up or holds
steady, as we said, and there is a choppiness as you go through the torpopause into
the stratosphere. This temperature change is an inversion, just like one 1,200 feet
above the ground early in the morning. The inversion makes sort of a lid, and if
there’s a jet stream, it will be fastest right under the tropopause. If this band of
strong wind contains turbulence, it will be roughest right at the trop and for a few
thousand feet below it. The depth of the region where the turbulence and wind are
strongest is a point of argument, but personally we like to give turbulence at the
trop a 4,000-foot berth, that is, fly 4,000 feet under it. This doesn’t avoid all the
turbulence, but makes it less bothersome.
Above the trop, in the stratosphere, the turbulence dies out within a very short
altitude range, usually 1,000 feet or less. If you get up out of the trop, it generally
becomes smoother quickly, and the wind decreases, too. If one has a strong
headwind, it is often possible to see it drop off dramatically as soon as one climbs
into the stratosphere. So if we’re trying to avoid headwinds, the temperature is
low enough, and our aircraft light enough for its given power to operate up there,
the place to fly is above the trop, and it’ll probably be smooth, too. You’ll also be
above much of the air traffic, allowing more direct routings. Pilots flying the
many superb modern corporate jets, with cruise altitudes commonly above 40,000
feet, usually can smugly relax in serenely smooth air, as they listen on the radio to
the rest of the flying world thrashing about in turbulence below, and who are
begging for altitudes to alleviate it.
Because jets fly between 28,000 and 45,000 feet or so, it’s simple to see that
they wander in and out of the tropopause as they cross over high- and lowpressure areas. This means that our current jets generally fly at the most annoying
altitudes. Every time you pass through the trop, it’s bumpy, and if there’s a lot of
wind or turbulence, it may be very bumpy.
Nuisance number two in the trop is the temperature change. You take off for a
long trip with a heavy airplane and plan to cruise at 33,000 feet. The weather
charts say it’s cool there, and the trop is well above you. Then, once in the air,
ATC says to climb to 35,000 feet. As you go through 34,000 feet, there’s a little
choppiness, and you can see a slight haze level. Your eyes dart to the outside air
temperature gauge just in time to see it go up to a “warm” -44 degrees C. The
airplane feels mushy in the “warm” air, and life is no longer beautiful. You are
above the trop.
A simplified view of a tropopause chart and visualization of its effects on a
Seattle-to-Chicago flight at 39,000 feet.
This is usually an inconvenience, and you may be able to stick it out and
stagger until the weight lowers through fuel use. On the other hand, the airplane’s
performance may become too compromised, either by “running out of power” or
we’re clipping the trop and it gets choppy. Then we’ll call ATC and tell them we
just cannot fly up there. Then they have the problem of squeezing us back into the
lower air traffic.
All this makes studying the tropopause charts (trop charts) very important
before a jet flight way up high. We’re looking for these things:
1. Trop heights
2. Trop temperatures
3. Trop wind direction and velocities
4. Vertical shear values
We are interested in the trop level, especially in the area of takeoff and where
we’ll reach climb altitude. For example, if the trop is supposed to be 33,000 feet
and its temperature is at the warmest our aircraft can handle, we may not be able
to climb higher immediately, even if we’d like to, because the temperature above
the trop will be at least the same, if not warmer. We may have to stay lower until
we fly into a higher trop area, or until we burn off fuel, are lighter, and have better
altitude capability.
Believe it or not, in today’s computerized weather, it is hard to find a trop
chart or data. A lot of that data, which one could eye for a look at potential
turbulence, is just published as potential turbulence areas. This is the dilemma of
our new world of computerized forecasts versus seeing the data as an experienced
pilot, applying it to previous experience, and then making our own wag at things.
Admittedly, these forecasting methods are becoming quite good, but it seems
these processes are encouraging pilots to be more responders to information, than
curious and knowledgeable participants of where, why and how they fly.
What was helpful on older charts was the vertical shear. It used to be on the
chart, in little boxes with numbers. We might see a value such as “4,” shown in
numeral form. This means the wind velocity changes 4 knots each 1,000 feet. We
remember that the value of 4 or more is generally considered enough shear to call
for turbulence, but as we said, it doesn’t always happen.
A trop chart has many characteristics similar to other pressure charts. If the
trop levels, shown in millibars, change greatly over a small distance, the winds
will be high speed, and it’ll be rough. In a steep slope like that, the temperatures
will change quickly and, as in a lusty cold front, there will be rough air. If the trop
levels make a sudden change in direction, it will be rough there, too. With today’s
computerization, if we find a trop chart, it’s worthwhile overlaying the trop chart
on a turbulence forecast chart for respective altitudes, giving us something we can
easily flick back and forth between, comparing and learning. There is an event
known as “tropopause break,” where the trop steps with two different heights, no
longer a connected portion of the atmosphere. That will be a trop height change
just about on top of itself. This is a potential turbulent area worth noting.
In summary, the trop information shows how high we’ll have to climb to be
out of rough air and strong winds, as well as where it might get turbulent as we
fly at trop altitude or transition through it. If we can climb above the trop, it gives
us a better envelope in which to operate our flight.
For high-flying jet aircraft, trop information is as important as the surface
chart in telling weather. These aircraft spend their time either near, in, or above
the trop, and familiarity with the phenomena is of utmost importance. We should
not plan such a flight without trop information, if at all possible, whether we get it
from computerized data, a phone call to the FSS or a flight-briefing service.
Pilots who fly at high altitudes should not be surprised by sudden turbulence if
they have studied the weather carefully, especially the trop charts information and
high-level pressure charts. After that, close observation in flight will show how
the forecast charts are working out and, if they are not, how to modify one’s flight.
Close monitoring of outside air temperature in flight provides further clues that
changes are about to occur. There’s little excuse for “surprise” turbulence.
Shear
Shear is an effect created by winds of different velocities and the cause of almost
all turbulence. We feel it when flying from one wind strength to another. Flying
from a strong headwind into a lighter wind, the airplane loses airspeed and must
get it back. At cruising speed, this isn’t much of a problem, but at low speeds
during an approach to landing, it can be significant.
At landing-approach speed, we are not too far from stall. An abrupt airspeed
loss, caused by flying out of a headwind, suddenly brings us much closer to the
stall. We sink. If we don’t do anything about this, it will take a long time to get the
speed back, many seconds, even a half-minute or more. In that time, we might get
too low and hit short of the runway. We’re not only talking of the infamous
thunderstorm wind shear events, but even a wind gradient issue on a seemingly
nice, but somewhat windy day.
When this speed loss occurs, we have to do something about it right away. We
pull the nose up to keep from sinking and put on more power to overcome the
drag from the pull-up. We can’t be bashful about quickly adding lots of power—
all of it if necessary. The pull-up can be quite severe in an extreme condition,
more so with highly powered aircraft like jets. In an event with severity, such as a
thunderstorm wind shear event, it may be necessary to pull up almost to the stall
angle of attack to get up and away from the ground. If the wind shear is strong, the
airplane’s initial angle of attack will be low, because of the downward airflow
from the storm. It is therefore necessary to change that to a big angle of attack, by
raising our aircraft’s pitch-angle, in order to get the necessary lift. The pitch angle,
what you see on the horizon, be it true or artificial, will be quite large, and it may
look pretty desperate, but the actual angle of attack, the relative wind, will not be
that extreme. During an event of this magnitude, maximum power must be used,
with throttles right up to the limit!
The task is not to exceed the stall angle of attack, and one will have to rely on
one’s sense of feel and the stall-warning device on the airplane. This later
situation usually has us flying so that we’re tickling the stall warning with an
occasional beep of the aural warning. There are instruments available today that
are specifically designed to help us fly through shear; they are usually found on
higher-end turbine aircraft, but with our rapidly changing technology they may
filter into smaller aircraft. It is important to note that certain shear and vortex
turbulence near a thunderstorm cannot be flown. The airplane cannot handle it,
special instruments or not! The only positive, safe answer is not to attempt
landing with a thunderstorm on or near the airport!
If strong shear is encountered, requiring large attitude and power changes to
combat it, a serious hazard then arises as the shear stabilizes and the pilot attempts
to continue the landing, instead of initiating a missed approach. Where the shear
avoidance maneuver is best done without trimming for the high attitude/angle of
attack and power situation, one can inadvertently do so. When this happens the
airplane is trimmed for this steep pitch attitude and excess power. To continue the
landing, retrim, get the power off the right amount, and slide back into a decent
approach slot for a safe landing requires some very difficult flying. This is
magnified in airplanes that require large stabilizer travel or have higher
performance characteristics, such as jets. Shear can also have a crosswind
component, which will quickly push the airplane away from the runway
centerline. So the pilot not only has to do some difficult trim, power, speed, and
rate-of-descent juggling, but also has to turn the airplane and get it lined up with
the runway, generally at low altitude. All this is very difficult flying and is
possibly where shear accidents are sometimes caused. So if a pilot is fortunate
enough to recover from the shear, it’s no time to press one’s luck and try to get
lined up and land. The smart maneuver is a go-around!
Shear is easier to cope with in a propeller airplane than a jet. The propeller
airplane, when we pour on power, gives thrust quickly; it also can produce an
immediate increase in airflow over the wing, depending on the aircraft’s
configuration, from the propeller wash, and therefore adds lift almost
immediately. The jet engine provides thrust only, which, if the throttle has been
pulled full back and the engine spun down, will take time, and a long time if it is
an older straight or low-bypass jet engine, in coming back to full power, so will
take longer to regain speed. While all pilots have to be alert for shear, the jet pilot
has to be particularly so. Also, lighter propeller aircraft, especially singles, don’t
have the power to weight ratio of turboprops and jets, so we can’t depend on the
same escape ability we hear of with turbine aircraft.
Where Is Shear?
Shear happens in various ways. With winds usually stronger aloft and weaker
near the ground, wind velocities change as we descend, producing shear. Shear
also occurs due to shifts in wind direction. In thunderstorms, when a front is
approaching an airport, we can easily get a wind change from southerly to
northerly in an instant that will make landing an exciting adventure. This can also
occur from winds spreading out from a later-stage thunderstorm’s down-flowing
air, which can happen quickly both in a storm situation and in a consequential
rapid wind shift.
More subtle, however, is a wind shift as we descend that changes a headwind
into a crosswind and effectively makes the airplane’s velocity lower. A few
hundred feet above the ground, the wind follows the isobars. That’s gradient wind
. But the surface friction of the wind running over the ground causes the wind to
flow more toward the low pressure, so the wind near the ground, instead of being
easterly as the gradient wind might be, will swing toward the northeast and north
as we descend. This, of course, cuts down its effective velocity and so produces a
shear effect with an airspeed loss.
It’s a good idea, when landing in a crosswind, to be conscious of the gradient
wind direction. Is the wind aloft more of a tailwind in the direction we’re landing
or a headwind? If it’s a tailwind, we may land too long or, worse, overshoot. For
example, we are landing to the west. There’s a north wind on the ground. The
wind aloft is east at about 40 knots at 1,000 feet. We are making our approach
with a whopping tailwind. Our ground speed is high. As we descend, the tailwind
decreases, but we only have a short period in which to get rid of a lot of ground
speed before we get to the runway. We tend to overshoot, and so we push the nose
over to get down to the runway’s end. Our speed increases, and lift becomes
excessive. It’s difficult to touch down on the runway; it would be wise to abandon
the approach. So we pull up and try landing to the east. Now we have a headwind
aloft, but as we descend we lose the headwind and some airspeed. Now we’ll have
to correct for sink and overcome the tendency to get below the glide path.
It’s obviously important to consider the gradient wind as we let down to land.
It will give us an idea of what to expect during the approach. Will we be
scampering and diving to get down and land within the airport—a tailwind
condition? Or will we be pouring on power, hoping to lift ourselves back on glide
path, in order to keep from undershooting—a headwind condition. The similarity
of these two examples is the decrease of either the headwind or tailwind, before
reaching the runway.
Sometimes the difference between the gradient wind and the surface wind can
be quite high, even more so at night than in daytime. A nighttime inversion makes
things seem still on the surface, but just above the inversion, the wind can be
swishing along at 50 knots if there is a strong pressure gradient. We must
therefore be wary of large differences between surface winds and winds aloft
when the gradient is tight and there is a strong inversion.
Warm fronts can create strong shear conditions when things on the ground
seem tranquil. First, let’s review the wind directions on both sides of a warm
front, as well as above and below the frontal surface. The frontal surface slopes
generally toward the north, about 300 to 1, which says that 300 miles north of the
surface front the front aloft will be at 5,280 feet above the ground. North of the
front and below the frontal surface, the winds are light from the northeast. South
of the front, and above the frontal surface, they are south to southwesterly and
often quite strong.
Now let’s place a warm front 30 miles south of Kansas City, Missouri, where
we will land. The surface wind at the airport is a gentle 10 knots or less and
northerly, but above 600 feet, the wind is southwest at 50 knots! So as we descend
toward 600 feet, we have a tailwind of 50 knots. Our rate of descent will be high
to stay on the approach path and so will our ground speed. We’re all set for an
overshoot. This isn’t just hypothesis. It has actually occurred at Kansas City.
A warm front situation is not especially bad, because we may have to go
around. It becomes serious when the pilot doesn’t go around and tries to make a
landing, touches down well along the runway, and goes off the end into who
knows what!
Overshoots may also put us in a position to undershoot. Descending fast,
trying to get down to the glideslope, we pull off all power. Then we run out of that
strong tailwind. Our ground speed slows, but airspeed increases from an effective
headwind, and we go above glideslope. In our effort to get back down, our power
is still reduced to idle. Then, sooner than we realize, the airplane goes below
glideslope, and we are undershooting! Now it’s pull the nose up and pour on
power. This can be quite a juggling act, especially on instruments.
The main thing we need to remember is that winds only a short distance above
the earth can be very different from winds on the surface. Tailwind-to-headwind,
wind reducing in descent, wind increasing in descent, or headwind-to-tailwind,
they all require different recovery techniques and aren’t restricted to warm fronts,
but can be experienced with cold fronts, nearby thunderstorms, mountain
downdrafts, and anything that can give the wind different vectors and velocities.
All this theoretical talk isn’t much good if we don’t know where fronts are or
if we suddenly run into shear conditions and don’t know why they are there. Then
what? First let’s recall the two basic things about shear:
• A headwind on landing tends to make us land short when wind velocity
decreases.
• A tailwind on landing tends to make us overshoot.
What we want to know is how strong the conditions are and how much the
wind will change during descent. In fancier language, what is the wind gradient?
This is part of our weather briefing, giving thought to wind changes with altitude
near the ground at takeoff and landing.
Once in the air, the sophisticated way to know wind gradient is by having
wind information on our instrumentation that tells wind direction, velocity, and
aircraft ground speed. We find all of this on glass-cockpit aircraft, and at least
ground speed on individual GPS systems and older IRS-equipped aircraft. The
wind direction needles allow us to see the wind direction change as we feel the
little choppiness in the air. The digital velocity tells us the magnitude of the wind
and the “watch out” factor. With only a ground speed reading, if we are on final
approach and our ground speed is lower than indicated airspeed, which is a
headwind, and the surface wind is not very strong, there’s a steep wind gradient.
This means we’d better be ready for that undershoot situation when we fly out of
the headwind lower in the approach. A high ground speed means a tailwind and
an overshoot. With actual wind direction and velocity available to the pilot, one
can compare it with the latest reported surface wind and know how much change
there will be in descent.
If we are without this helpful wind data, and we’re on an ILS or any precision
approach of normal three-degree glideslope, it’s fairly easy to get an idea of
what’s going on by our rate of descent. Let’s say our approach speed is 120 knots.
To make good a three-degree glideslope, without wind, we’ll descend about 600
feet per minute. So, if we find that it only requires 400 feet per minute to stay on
the glideslope, we’ve got about a 40-knot headwind; in other words, an 80-knot
ground speed needing a 400 feet per minute glides-lope. If the surface wind is 10
knots, then somewhere during descent, we’re going to lose 30 knots and have to
get power on and scramble to keep from getting too low. On the other hand, if our
necessary descent rate to stay on the glideslope is near 800 feet per minute, then
we’ve got a 40-knot tailwind, and it’s going to be a scramble not to overshoot.
Required descent rates versus ground speed often are listed on the bottom of
approach plates, but if they aren’t, there’s a formula to help decide what the
ground speed should be. Half the ground speed times ten equals the descent rate,
or nearly so. Take our 120 knots; half of that is 60, which times 10 equals 600 feet
per minute. This is 36 feet per minute short, but is pretty close as the VSI reads.
This, of course, is for a normal three-degree glideslope.
We can do it backward: if we’re coming down the glideslope at, say, 900 feet
per minute, we can divide that by 10, which equals 90, and multiply that by 2,
which comes out 180, and that’s our ground speed. If our normal speed is 120
knots, we’ve got a 60-knot tailwind!
These numbers are for true airspeed, which if we’re near sea level and the
temperatures aren’t wildly off standard, will be pretty good. If we’re landing at a
5,000-feet-above-sea-level airport, however, we’ll have to compute what the true
airspeed (TAS) is for our 120-knot indicated airspeed (IAS) approach speed. A
wag is 2 percent increase over indicated per 1,000 feet above sea level: at 5,000
feet that’s 2% × 5 = 10%, and for 120 knots, that’s 12 knots. So we have a true
airspeed of 132 knots, give or take.
Formulas, put up somewhere handy in the cockpit, will also be useful to help
figure ahead of time the descent rate you’ll have to use coming down on the ILS
when you have a rough idea of the descent winds. For one’s particular airplane,
with which we always use a certain approach speed, it’s possible to mark the
ground speeds opposite the appropriate descent rates next to the vertical speed
indicator—if we’re flying a good old round-dial instrument system. With a glass
cockpit, despite the myriad of guidance, you’ll still have that low-level wind
dance that is cured only by good flying ability—and judgment of whether it won’t
work and it’s smart to go around.
A visual approach is more difficult, because there isn’t any exact glideslope
guidance, unless there’s a Visual Approach Slope Indicator (VASI ) or Precision
Approach Path Indicator (PAPI ), and other types, which are all grouped as Visual
Glide Slope Indicators (VGSI ) in this acronym world, which you can pick up well
out from the runway. Staying on a VGSI glide path, and seeing what rate of
descent is needed to stay with the glide path, is the same as coming down an ILS
glide path of three degrees, if the VGSI is matched to the same angle—and most
of them are.
An all-visual approach, without a visual or electronic glide path reference to
help, means getting back to basics. If we can pick a spot on the ground we want to
land on, and then watch it in relation to our descent path, we know how we are
doing. If the spot climbs in the windshield, we’re undershooting, and if it
descends, we’re overshooting. So it’s a sort of visual glide path. If we notice it’s
taking lots of power and a higher-than-normal nose attitude, we’ve got a
headwind. However, if the nose is down, and we keep wanting to pull off power,
we have a tailwind.
It isn’t always possible to pick a spot in poor visibility or way out from the
airport. If it isn’t, then it’s eyeballing the situation and using one’s good seat-ofthe-pants feeling and visual cues that come naturally over years of experience. If
we’re dragging in, there’s a headwind, and vice versa.
Another type of shear is caused by gusty winds. It’s obvious that a wind
blowing 10 knots and gusting to 20 can give one a very quick airspeed change of
10 knots. That’s why, on gusty days, it is wise to carry extra airspeed to take care
of these “sinkers” on approach, as a gust dies down and leaves one low on
airspeed. One popular correction factor takes the normal approach speed and adds
half the gust velocity as a cushion during gusty conditions, plus another 5 knots if
the wind is above 15 or 20 knots.
Shear is often overlooked as a takeoff hazard, but it’s as important then as in
landing. There have been cases where a takeoff was made into a headwind with a
strong opposite wind (tailwind) whistling along just above the ground and resulted
in an accident. If flying from an airport with ATIS information saying “wind shear
advisories in effect,” we take it seriously and plan our takeoff accordingly, even if
it means reconsidering the departure altogether. This, of course, applies as a
heads-up to arrivals, as well.
If there is a front of any sort near the departure point, we should carefully
consider a wind shift, looking for information of frontal location, NEXRAD, if we
have it, (considering a 10 to 20 minute delay in the data), or possibly an
ATIS/ASOS/AWOS from a nearby, upwind airport as to timing of a wind shift,
any precipitation, and so on. If really close, it’s worth looking upwind for blowing
smoke, dust or dirt, its direction and ferocity, before taking off. With a
thunderstorm nearby, we should be prepared for a wind direction change after
takeoff, let alone the turbulence and all else that makes a close thunderstorm
departure something to reconsider. A thunderstorm, realistically, is the weather
most likely to be violent enough to make the dramatic wind shift that causes
trouble. To be pedantic and repetitive, a thunderstorm near the airport, landing or
taking off, is a very real danger, and sometimes one that cannot be flown
successfully. To say it as emphatically as possible, do not land or take off close to
thunderstorms. Our present use of radar, both in the airplane and by ATC, tends to
have airplanes cutting in too close to thunderstorms. Often a mild-looking storm
just off the approach path can suddenly, in moments, reach the point where it
dumps water and wind in violent fashion. Thunderstorms are not static; they are
constantly changing. They are something to give wide berth. The accidents that
have occurred on approach to landing and takeoff are a gruesome enough proof.
What do we do about all this? If the front or thunderstorm is close and strong,
let’s wait until it passes. If we get caught, because we didn’t think it was that bad,
then consider that a loss of 50 knots, or a severe downdraft, is going to require an
excess of speed as soon as possible after getting airborne. We want to get that
excess quickly, remembering, of course, not to fly back into the ground or get too
low when we’re taking off into the unseen abyss of night, or on instruments, while
in the process.
Sudden airspeed changes due to shear, bumps, or whatever affect the aircraft’s
pitch attitudes. Two points: when getting a positive airspeed increase, or rising
gust, the nose will pitch up; when going from a headwind to a tailwind, or
descending gust, the nose will pitch down. So we’re taking off into a headwind
and suddenly, right off the ground, we get an airspeed loss from a descending
gust. Airspeed drops, and so does the nose. We should be prepared for this and, as
in all flying, hang on to the pitch attitude we want. This is also why we do not
want to chase these pitch changes with trim. Having flown a lot of these scenarios
in simulators, you want to just fly the airplane with whatever force you need and
as much finesse as possible, so when things return to normal, the airplane isn’t all
screwed up with wild control forces, which, as said before, only adds to the
event’s problems.
Thermals
There’s another effect that isn’t strictly shear but acts in much the same way. It
comes from thermals, the kind glider pilots look for: rising pieces of air.
On a summer day, we approach a runway. Perhaps there isn’t much wind at all,
but before reaching the runway, we get a bit of sink and have to pull the nose up
and add power. Then we cross the runway and suddenly seem to have excess lift
and float for a long distance before the airplane will touch down. What happened?
Chances are that this was an approach to a paved runway surrounded by grass
or other vegetation. If we could see air circulation, we’d notice lifting air coming
up off the paved runway and then (because when some air goes up, some other air
must come down to replace it), we’d probably see air sinking over the grass
adjacent to the runway. On our approach we’d fly through the sinking air over the
vegetation; then, over the runway, we’d fly into the lifting air that would want to
keep us up. The opposite will occur at night, with lift over the warmth-retaining
vegetation and sink over the cooling runway. That’s why we sometimes go clump
in a hard landing at night and wonder why. We flew into sinking air. The night
effect, however, isn’t as strong as the daytime effect.
This also works approaching a runway right at the end of a body of water;
sometimes even more so. One day, (ROB) approaching Boston’s runway 27, in a
727, on a very windy day with lots of thermals, this sink–lift–sink routine added
another sequence at about touchdown, but we didn’t touch—we kissed and
ballooned. It felt like a J-3 Cub, buoyantly floating along, so much so that milking
the 727 down before running out of runway seemed very unlikely. Blasting off in
a go-around, we caught a glance overhead of a glider pilot’s dream—a beautiful
dark-bottomed summer cumulus, full of lift.
The important part of all this is that when sink occurs short of a runway, be it
due to speed loss from shear or a thermal, we must be ready to use power and
keep our airplane flying on the approach path which we have selected, either
visual or instrument, and not allow it to land short. Conversely, if you run into lift
and find yourself floating along like you’re sitting on a cloud, without excessive
runway length, make that go-around.
12
VFR—Flying Weather Visually
Some of us fly VFR because we don’t know how to fly instruments. There isn’t
any doubt that a pilot who is serious about using an aircraft for transportation
should learn instrument flying and obtain a rating as soon as possible. It makes
flying safer, more useful and offers the enjoyable satisfaction of learning a new
level of challenge and proficiency.
Knowing instrument flying makes for safer flying because a pilot doesn’t get
trapped in bad situations. If cornered, you pour on power, pull up to a safe height,
and think over what is best to do. It isn’t necessary to poke along between
mountains or duck communication towers, windmills, and other skyward
intrusions when ceilings and visibilities are low. Most of the time, an instrumentrated pilot can be on top, in sunshine, enjoying the flight, rather than nervously
and dangerously picking along in reduced visibility.
In the early days of airmail—the days of open cockpits, helmet, and goggles
—the pilots didn’t fly instruments; they dangerously stayed “contact” and strained
eyes and nerves trying to see what was coming up. That was when the Allegheny
Mountains were called Hell’s Stretch. Pilots plowed into them regularly, leaving
broken bodies and airplanes on the rugged slopes. In the first year of the airmail
service, as many pilots were lost as were employed by the service.
It pays to be instrument qualified, and every day it becomes more necessary,
as the airway system grows in complexity. Modern aircraft equipment has become
more sophisticated and compatible with weather flying, so that instrument flying
is an integral part of all flying. To restrict oneself to VFR flight means one will
have less and less area to fly in, and someday VFR flight may only be possible in
limited zones under strict control. It also means we are not using general aviation
to its full potential. Aside from all that, an instrument-qualified pilot is a safer
pilot, and it is difficult for us to visualize being in the sky without the ability to fly
by instruments.
Night flying, surprisingly, is often instrument flying. Take off at night, down a
lighted runway, then, as the runway falls behind, we are suddenly in a black hole
with no visual reference. We’re on instruments! Whether right after takeoff or for
that matter in any phase of flight, seconds of disorientation from improper “blindflying” instrument response can be fatal. Also, as said before and will continue to
be harped upon, an autopilot is not an acceptable bridge for the pilot unable to
manage a hand-flown aircraft in instrument flight. Overall, the record shows that
more VFR accidents occur at night than in the daytime. If we’re going to fly at
night, we need to know how to fly by instruments.
VFR
There’s still a lot of VFR flying, and as a matter of fact most flying is VFR. There
isn’t anything wrong with it, if the limitations are known and followed. First,
always, is the fact that in flying VFR one must see! Low clouds and poor
visibilities make this difficult. Rough terrain makes it worse. A key to safe VFR is
not to get in a position where the visibility is so bad we cannot see enough to
make a normal 180° turn and get out. It’s worth trying on a clear day, noting
points on the ground, to see how much room it takes to turn. Then, at least double
that distance for a cushion in actual weather. However, that is still pretty lousy
visibility, and hopefully, we do not let ourselves get into such a predicament, but
at least we now have sense of when that visibility is too low and we had better
turn around.
The Famous 180
Two things are important. One is that the weather will not always have a nice,
clear-cut edge that separates VFR from IFR, so a 180° turn may not always bring
us right back to VFR conditions. While we’ve been sneaking along VFR, the IFR
weather may have been sneaking along right behind us, and when the 180° turn is
accomplished, we’re still face-to-face with marginal to below VFR. Keep an
occasional watch behind to see what’s sneaking up on us. Point two is that limited
instrument flying ability, which came with that minimum of instrument
instruction when first learning to fly—including being shown that 180° turn to get
us out of bad weather—is not sufficient to get involved with IFR flying. That
minimum instrument flying instruction was for a dire emergency only! With
rapidly deteriorating weather, a simple 180 can turn into a full instrument workout
and we’d better be able to handle it. If committed to a 180° turn, and the visibility
reference is poor, concentrate on the instruments: holding altitude, maintaining
airspeed, keeping a proper bank angle until the return heading is achieved. But
remember, without full instrument flying ability, this is very dangerous stuff!
Flying into the picture: IFR yes, VFR no. It’s obvious the weather ahead is
worsening. This was near Tulsa, Oklahoma, with a summertime warm front and
thunderstorms. A pilot should have a good picture of the weather and actual
reports before poking around in this.
In VFR flying, it is especially important to be flying toward better weather.
VFR flying demands a good knowledge of the weather situation, and a VFR pilot
should study weather in advance as much, if not more, than an IFR pilot. A nice
day at the takeoff point doesn’t mean it will be nice for the entire route.
The VFR pilot must be especially aware of any possible weather deterioration.
If it goes sour, staying “contact” is a must, and this can mean getting too low in
reduced visibility—a perfect formula for trouble! The IFR pilot is interested in
trends, but deterioration may mean simply shooting a low approach or going to an
alternate. When the weather goes sour, the IFR pilot does not get into trouble as
deeply or quickly as the VFR pilot. So the VFR pilot needs a good look at the
synoptic situation: where fronts are and their expected movements, plus the en
route and terminal forecasts, as well as a good look at satellite, radar, and weather
depiction data. We also remember our admonition about areas marked MVFR—
Marginal VFR. Unless the trend is for improvement, stay out of these areas and, at
best, keep a sharp eye on what the weather is doing when flying through MVFR
areas.
Basic weather rules for a VFR flight are these: Fly toward improving weather;
do not fly toward approaching fronts. Especially do not attempt to “beat” a front
to your destination. Be extra conscious of destination forecasts when flying
toward evening, shorelines, heavy industrial areas, and mountainous regions. Also
take special care in spring and fall, when the days are warm and the nights cool,
particularly if there’s a lot of moisture on the ground and in the air near the
ground. We get this when lots of rain has fallen, and particularly when there is
snow on the ground that has been rained on or subjected to melting during the
day. We all know the feel of those clammy, cold nights and moisture-laden air;
they easily make fog.
If there isn’t any frontal condition, but cloud decks are forecast because of
postfrontal air masses, be alert to the fact that clouds in mountainous areas will
tend to be overcast and close to or on the mountaintops. If the air mass is
vigorous, there will be showers and low visibilities. The weather will be as
difficult as a front.
Flying in mountainous regions requires more visibility than in flat terrain,
because clouds tend to hang on mountains and blend in, so mountains and clouds
often look alike. The slopes are difficult to see, and one comes up on them fast,
even at 100 miles an hour.
A good rule is that if you cannot see the mountaintops, with space between
them and the cloud bases, it’s a poor time to be flying. There are, however, some
conditions where there is excellent visibility, 20 miles or more, and we can fly
down valleys with the mountaintops in cloud. But the forecast must be solid gold
to stay good! The first snowflake or raindrop and it’s time to find a place to land.
And always be certain there’s an entry and exit to the valley, because you cannot
climb over the mountains to get out. Flying into a cul-de-sac—a dead-end valley
—is bad, bad news.
When checking weather for flight across mountainous areas, be aware that the
METARs or an ASOS/AWOS may show adequate ceiling and visibility at
departure and destination airports, but lack reports for areas en route that may be
much higher terrain than departure or arrival airports. There might be adequate
ceiling and visibility at the departure and arrival, but zero-zero in high terrain en
route. Such was the case in our picture that looks on top of valley fog, a bit further
in the chapter (on page 190).
A Point to Remember
A VFR point worth thinking about is that the closer one gets to the cloud base, the
worse the visibility. As the ceiling squeezes a pilot lower and lower, the tendency
is to try and stay as high as possible. In doing so, the airplane crowds the base of
the overcast. (If we’re not careful, this can become illegal, in relation to
regulations of VFR flight and cloud separation.) Also, the base of a cloud isn’t
clean-cut; mist and shredded hunks of vapor, like a gossamer veil, hang down
below the solid part. Pilots can be flying in this area and see the ground straight
down, but ahead, because we are looking through a lot of ragged stuff hanging
from the cloud base, the visibility is low or nil. Descending a little, sometimes
only 50 feet, the visibility may suddenly improve. If it doesn’t improve in 50 to
100 feet, then the bottom of the cloud isn’t the problem, and it will not pay to go
lower; it might actually be dangerous because of getting too close to the ground.
We may be boxed into real trouble.
Snow Is Different
This idea of going a little bit lower to improve the visibility doesn’t hold true in
snow. Often, in snow, the ceiling is quite high. Snow generally forms directly
from water vapor without any cloud process, and one doesn’t get “in” a cloud. In
professional jargon, this process is called sublimation . Because there isn’t cloud
in this kind of snow, there generally isn’t any ice. It takes the supercooled water in
a cloud to make ice: no cloud, no ice (except in the case of freezing rain).
Therefore, if a pilot is in snow with the ground visible, he or she can pretty well
relax as far as ice on wings and propeller is concerned.
Snow can come from nimbostratus clouds and snow showers from cumulus.
These clouds are easy to avoid—generally by flying on top. Nimbostratus, or
stratocumulus, is the kind we find over mountains after a cold front. Snow
showers in cumulus would be in unstable air, so on top is again the place to be,
but the tops may be high. The clouds that have snow must contain supercooled
water, and they get that by the lifting caused by strong instability or in air that’s
been lifted mechanically by wind pushing it up a mountainside. Generally,
however, there isn’t ice in large areas of snow. If ice forms, you are either in a
lower cloud deck—and hopefully finding this out during an IFR flight—which
you can top, or you are near the frontal surface. More on that later.
The heat of the engine and windshield may cause snow to melt and refreeze as
slush, just as on an automobile windshield on a snowy day. Because of this, a
pilot flying a piston-engine aircraft has to keep an eye out for carburetor ice all
the time and for engine intakes getting plugged up after a long period of flying in
snow.
Flying in snow caused by overrunning air ahead of a warm front, which is
usually a general area of snow, one can see the ground straight down from quite a
few thousand feet. Of course, the visibility ahead will be very poor, because we’re
looking through a lot of snow. Because the snow forms aloft and falls to the
ground, the restriction in visibility caused by the snow takes in all the sky, so
going lower will not improve visibility. People are sometimes fooled by snow and
fly lower and lower, because they can see the ground straight down, thinking they
should be able to get “under” the stuff. In fact, they cannot get “under” it and
sometimes get hurt trying to do so. A pure VFR pilot had best stay out of snow
areas, because the visibility will be poor regardless of the ceiling. Once snow
starts, even light snow, the visibility will become poor in a short time.
A VFR pilot prowling along under leaden skies will often have good visibility,
but when snow starts and the first white streaks go by, it’s time, right then, to
think about going elsewhere or finding a place to land. The first flakes of snow
are almost always a loud and clear signal that things are going to get worse. It’s
no time to keep poking ahead and hoping for better.
Sometimes, ahead of warm fronts, snow begins to fall very quickly in a fairly
wide area, 100 miles wide or more, so that one must consider the unpleasant
possibility that a 180° turn will not get us out of the condition, because the snow
may start, at the same time, all around us and for many miles behind. All this
relates back to the point that we should study weather in advance and know, in our
mind, what could happen and which way to duck if it does. When precipitation
begins, especially snow, a pilot shouldn’t sit fat, dumb, and happy until things get
worse. It’s time to do something before that, whether trying to turn around or go
somewhere else and land. This potential situation is another good argument for
excellent navigation, keeping sharp awareness of our position and where the
nearest airport is located. This means geographically—terrain, built-up areas,
obstructions, air-space restrictions, and so forth—from sectional charts, whether
paper or electronically displayed, and not just a line on a featureless GPS screen,
or heading and distance to a point.
Keep Calm
When we say go somewhere and land, we don’t mean to do so in a panicky
fashion. The worst thing we can do, in any situation, is get frantic, dash for
Mother Earth, and land in the first field that comes along. If possible, we ought to
stick to airports, and ones that fit the airplane. Of course, this isn’t always
possible, and more on that when we discuss “Not Only Airports” in a couple of
pages.
More Snow
Just to confuse things, snow can also be found falling out of clouds. This
condition is generally found in air-mass weather, such as a stratocumulus deck
behind a cold front. Snow falls from the clouds, and the clouds have ice in them.
In mountains, the higher ridges are in the clouds, and these are conditions a VFR
pilot should avoid.
The mountains of Pennsylvania, after a cold front passage in winter, are
generally cloud-covered and get lots of snow, with the visibility poor to zero. It’s
not a frontal condition, but nevertheless it’s a tough one for VFR. It’s not a place
to try to fly VFR underneath the clouds. The only way is on top, and that will
require an instrument climb with ice in the clouds, their tops 8,000 to 12,000 feet,
or even higher over tall mountain terrain, such as the western United States.
Low stratus clouds, giving poor ceilings, increase as one gets closer to a front.
In these clouds, there are snow and ice; the snow, however, will be falling through
the clouds from someplace above them. A pilot will be in snow, but this time the
ground will only be occasionally visible through breaks. There will be ice in the
stratus clouds. At best, this isn’t a good place for VFR flying. We’ll talk more
about it later when discussing instrument flying in weather. We can say, in
passing, that an instrument-rated pilot can pull up and get on top of these iceproducing clouds, assuming the aircraft can handle ice, both physically and
legally, in order to climb through it. Such IFR flight will be between layers but
mostly on instruments, because the snow will cut visibility practically to zero. It
will be a white-gray world without reference—for instrument pilots only.
Towers
VFR pilots sneaking along over flat country have to be wary of television (TV)
and radio transmission towers. They stick up dangerously high, not uncommonly
to 1,000 feet above the ground, and some reach 2,000 feet. Add their supporting
cables, extending way out to their sides, they are skinny and nearly invisible, even
those with strobe lights—at least until they are suddenly right in front of us, with
no place to go. Also, the communications folks have a way of putting them on
mountaintops. Lower towers, such as those for microwave and cell phone service,
usually under 1,000 feet above ground, are everywhere—especially on the peaks
of hills and mountains.
There is a proliferation of seemingly innocuous towers under 200 feet above
ground. Used for meteorological and other information, their “under-200” height
falls outside the FAA’s regulations for tall structures requiring strobe lights,
brightly painted structures, and, worse, notification of their installation. That
means they are not on the maps and the GPS units that display obstacles. They
spring up overnight, at the whim of those desiring their utility. In flat lands, these
towers have been fatal to agricultural aircraft and helicopter operations, but
consider when these towers under 200 feet tall, as well as other towers, even if
taller and noted on maps and GPS units, are placed on that hill or mountaintop
you are grimly sneaking over in lousy visibility and low-hanging scud that also
may be hiding those towers.
We may think sneaking around so low to the ground is not our style, however,
it is amazing how quick and desperate things can get when we push into
compromising weather. Suddenly, we’re stuck, knowing we can’t stop in mid air,
but the sky and ground are rapidly squeezing together.
VFR Navigation—and the Important Map
On any VFR flight, the pilot should know, at any time, the accurate location of the
aircraft, preferably down to the mile. Yes, its old-school precision, but this theory
will eventually prove its worth. We can’t afford it any other way. This means any
VFR pilot must be sharp with themselves navigating by a sectional map—or chart
if you wish—even if an electronic one, and not through dependence on a GPS or
VOR navigating for them; instead, finger on the map and looking out the window.
If a pilot isn’t well honed at precise VFR navigation, one should consider raising
their ceiling and visibility requirements to a higher value; say 3,000 feet and 10
miles as a starter.
With the advent of GPS navigation, we know where we are at a moment’s
glance. Or do we? Not all GPS navigation systems are created equal; in this case,
meaning how the information is displayed. Depending how fancy our GPS is, it
might just have a line on a screen, or it could be the animated display of terrain,
obstacles, airports, airspace, and even weather information. However, for VFR
flight, we should have all the information we need, for the navigation process,
located in one place. The best, most user suitable and complete source for this
official information is a sectional chart, whether a good old paper one or an
electronically displayed version. Probably the most ideal arrangement for VFRflying is one of the GPS displays that show our position on a moving map display,
over an official electronically displayed sectional chart. Anything less than current
sectional chart information, whether paper or electric, is really not an adequate
choice for VFR flight.
As mentioned earlier, the system of VFR navigation is different than IFR
because we have to maintain at least legal visual conditions, with better than legal
as more prudent. VFR also means it’s our responsibility to avoid unauthorized
airspace intrusion, but most important is not running into anything, whether it is
terrain, obstacles, or other aircraft. Our reference to all this, except for other
aircraft, is off a sectional chart, but ultimately must be seen for real, by our eyes
looking out of the aircraft, not at an electronic display.
Up high on a lovely clear day, our VFR flight may be following IFR routes
with ATC flight-following, which can give us terrain clearance and helps avoid
other aircraft. This means we’re probably navigating with either VORs or a GPS.
But since we’re VFR, an airway facility IFR chart is not an adequate VFR chart,
just as a line on a vague GPS screen isn’t either. One reason is obvious lack of
VFR information, but also because we can’t guarantee the weather will let us stay
high and in the clear, instead the weather deteriorates, forcing us to descend into
the many concerns we reference from sectional charts.
Let’s say our clear VFR day has caught up to a weather system. Or, maybe we
started the flight earlier in the morning, then in a couple of hours the sun has
caused thermals to form cumulus, and they have gone from scattered to broken
and now we have to get below them before we’re trapped on top. All of a sudden
we’re down below the haze layer, the visibility is less, we’re at conflict altitude to
airspace, and below IFR altitudes that give us terrain clearance. Down low we
don’t see as far and there aren’t as many clues available to help interpret a map.
Our area of vision takes in a smaller area, even with good visibility, but even
worse in poor weather where the visual range is even less.
Now those cumulus start to spit rain or snow showers, the ceiling lowers
further because we’re in hilly terrain, and we’re spooking around no more than a
couple of thousand feet above the ground in visibility pushing the three mile VFR
limit. At best, we’d better have an accurate altimeter setting, which we find by
making ourselves even busier in the cockpit, looking for ASOS/AWOS or VOR
frequencies and tuning them, or fiddling with electronics to call them up data on
an MFD. If we’re really not clever, and things get really tight with visibility and
ceiling, we may have little if any time to fly the airplane, check the map for
information, and not hit anything—let alone fiddle with electronics. I (ROB) will
tell you this is not a conjecture. I’m not proud of it, and the unacceptable
disclaimer is that it was decades ago where fleetness of imprudent youth, coupled
with a docile Cessna 182, being over home country, and undeserving luck, saved
the day.
Obviously, if the visibility and/or ceiling is that lousy, we’d best be on top of
our navigation and terrain awareness, heading for a nice airport, where we land
and wait out the bad weather. But let’s say the weather is okay to press on,
although not stellar. This is where we must have that sectional chart information.
The list of the chart’s offerings is huge, but again key items include terrain,
towers, airspace issues, navigation and communication information, as well as that
ever important airport to where we can run if things get tough. And constantly
knowing position also means knowing where that nearest airport is located; it
might be one recently passed, off to the side, or not far ahead, but we ought to
know where it is.
With GPS we have some help with this closest-airport process. One is the
button we can push to find that closest airport. However, that will give us a direct
routing to the airport, which might be over unapproved airspace (also usually
shown on GPS) or more importantly terrain we’re above and can’t see because of
poor visibility or darkness. Again, we have to know where we are! Another goodie
of GPS is the terrain function, which warns us of terrain, towers and other
intrusions into the sky in front of us. And that “synthetic vision” displayed on a
PFD? It’s great reference too, but none of these warnings are approved for terrain
navigation! Again, our eyes need to identify what’s outside, not what’s on an
electronic screen. And the accuracy of these GPS-displayed terrain features is only
as good as the currency of the GPS’s databases. So again, reference to that map is
golden, but then they have to be current, too!
A theory worth considering concerns navigating by paper sectional chart
versus GPS moving map. Using the map means we’re looking in at the map, out at
the sky and terrain, flying the airplane, then back inside to the map and so forth.
Done correctly, we’re really on the ball! With a GPS moving-map display, a lot of
the work is being done for us, breading temptation to “follow the bouncing ball,”
instead of the proactive event with navigation awareness. Also, it’s temptation that
entices us to look inside more, not just at the moving-map but for button pushing
and fiddling with electronics, taking just quick glances outside for aircraft
operation instead of overall awareness or sky and terrain. And where are we with
that within-a-mile navigation accuracy…referencing outside, not that little point
on the moving map? This doesn’t mean we shouldn’t use the moving map, but
make sure we discipline ourselves to be, when VFR, outside-pilots.
We might want to think about using autopilots when down low and dirty, VFR
in lousy weather. It can give us time to better manage the whole situation,
spending more time with navigation and other stuff. On the other hand, if the
weather is getting really poor, we should fly mostly with our eyes outside, both
for flight and location reference; especially if we don’t want that fancy autopilot
driving us into a hill or tower. So, down low and in poor weather, there’s
argument to it being a hand-flown, navigating, and terrain avoiding issue, being
able to maneuver efficiently and relatively quickly; not putting delay in our
maneuvering by twisting a knob, then wait for that command to manuver the
airplane through autopilot-servos. Handflying can arguably function almost
subconsciously, with imminent reaction.
On maneuvering in tight quarters, it’s one thing to be doing it in a very docile,
“old-wing” type of airplane, especially if you had big fowler flaps that could slow
you down in tight situations. Like any airplane, you have limits and can’t get lazy
about them but it’s more forgiving than some of the newer, thin-fast wings, which
with their faster speeds also have wider turning radius; a consideration if in tight
quarters.
In high-terrain we need to keep in mind high-tension wires that may cross
valleys, following railroads that may go into a tunnel of terrain hidden by cloud,
or those towers we’ve mentioned. Crowding a mountainside too closely could
possibly cause one to clip the wires of a ski or utility lift that may be difficult to
see, summer and winter. A number of glider accidents have occurred in the Alps
in exactly this manner. This kind of flying is desperate, not to mention illegal, and
no one should be doing it. We mention it only in case we get ourselves in such a
fix and, illegal or not, wanting out in one piece!
A few last thoughts on sectional charts. One is to have a current set—and as
said before and will come up again—that is organized and folded to our route,
easily accessible whether it’s primary reference, or backup to electronic sectional
information. The biggest reason—if that GPS quits, we’d better pick up with that
paper chart right away, because, unless we know the country we’re over, in just
minutes we’ll be far enough down the road to being very lost. Another benefit of
sectionals is that they are excellent for planning our flights, spreading them out
before the trip, looking at the terrain, airspace and consider our weather briefing
information in relation to the geography and route. And lastly, handing a sectional
chart to our passengers, with the route drawn on it, can engage them in the flight.
This is beneficial whether they’re curious, a bit nervous, or prone to airsickness…
it can keep them occupied.
So flying cross-country as a VFR pilot? Use that sectional information,
practice navigation, be smart, then humble enough to accept a modest motel in
strange port-of-call, as an appreciated alternative to flying VFR in risky, bad
weather.
Not Only Airports
If we’re in a jam, stuck with IFR and no place to go, there may be relief right
under us. It isn’t always necessary to land on an airport, and the “gotta get to an
airport” fixation may work us into a deeper jam than picking a field and landing in
it.
Landing at other than an airport may seem well outside the box, but it does not
have to be. Realizing that many of today’s aircraft are the same designs, or at least
have similar landing speeds, of those decades ago, when field landings were not
such a distant idea. I (ROB) remember a day when just a kid, where my father
said we should drive to the golf course and check out a Globe Swift—a neat twoseat, low-wing little airplane. The weather was low in bad visibility, and the VFR
pilot was smart enough to pick the long par 5, 15 th hole, as his “ace-in-the-hole”
(pun intended), for safe landing. He must have known the alternative was to risk
running into the fog-shrouded Watchung Hills of central New Jersey. The next
day, in clear skies, he got the okay to takeoff, weaving around the 15 th tee, going
safely on his way.
When one considers many fields are just unpaved runways, off-airport
landings seem more palatable. This is a place to use short and soft field-landing
techniques. Glider pilots land in fields, and learning how is part of their training.
In glider talk, it’s called “off-field landing,” meaning off-airport. Admittedly,
gliders—or sailplanes in this day and age—have the advantage from somewhat
slower landing speeds and usually having excellent dive brakes to get us down
over obstacles; and less mass to get stopped. General aviation aircraft like a
Cessna 172 with big flaps can slow down and land pretty short. In any event,
knowing how to do this is another reason for power pilots to consider some glider
training and experience—plus it is fun; the soaring, that is!
Of course, landing in a field or pasture does need care and some planning,
with the realization that there are cases that might lead to a bit of damage, such as
messing up a nose wheel. However, we are making a choice of getting on the
ground safely in lieu of flying along until we can’t see where we are going,
running into something, or losing control of the airplane in instrument conditions.
The accident reports, often fatal, state the cause as “continued VFR into
Instrument conditions.” Let’s take a look at picking a place to land “off-field.”
First, take it easy and take your time. Don’t rush! Look the field over for
rocks, ditches, large wet areas, and severe undulations. Check its slope, both the
long way and side to side. It is usually best to land up a slope, even with some
tailwind, versus your airplane’s glide angle chasing the slope and eventually
running out of room to land. Side slopes can be tricky for these, we should plan to
land in a gently banked, arched diagonal to the slope, starting uphill and ending
the landing roll before starting back down the hill.
As to what we look for in an off-airport landing, our favorite is a nice stubble
field of cut hay or wheat, and hopefully not wet; darker areas in a field hint of
moist areas. Beware after rains and snowmelt. Plowed field issues depend on how
deep the dirt is, or again, if it’s wet. If in furrows, whether plowed-field or crops,
land with them—not across—trying to put the wheels in the furrows, especially
the nose wheel. (Stubble and plowed fields cause little if any crop damage.)
Higher crops can grab a low wing and possibly cause a ground loop, so we want
to keep our wing’s level and be slow but still under control. Mature corn with ears
does not do favors for leading edges. High grass and uncut fields are unknown
quantities as to possible gopher holes, rocks, and so on. Hidden ditches and
fences are unwelcome surprises, especially barbed wire. With low canopies, as in
gliders, barbed wire acts like a horizontal guillotine. Deeper snow, especially with
a crust, is a natural arresting hook, but you risk gear damage and maybe flipping
the aircraft; beautiful snowy countryside is suddenly not so pretty if an engine
quits.
Roads with lots of traffic, lights, signs and so forth are grim choice. Out West,
with wide right-of-ways, roads are great runways; just avoid culverts and curves,
as that’s where signs and reflector posts go, and keep a sharp eye for any along the
straights. If at all possible, land down the centerline, for wingtip clearance; don’t
depend on it, so land between stakes and signs. Interstates can be good open
spaces, but we know vehicles are plenty, are going fast, and least expect an
airplane to land in front of them. Keep an eye out and plan accordingly.
The benefit to an off-airport landing for avoidance of bad weather is that we’ll
most likely be under power, have time to check things out, and maybe even make
a quick low pass, as long as we don’t get sidetracked and spin in on the go around.
Check carefully for obstructions, especially wires that may be concealed by trees,
or be suspicious on seeing a telephone pole in a field; look for where wires
connected to the pole pass across the field. Then, when you decide it’s time to
land, do a proper and normal pattern: downwind, base, and final, all the while
looking the field over for any further obstructions and rough surface that may
become apparent as you get lower.
Again, landing away from an airport in a field may be far safer than trying to
work along in bad visibility and ceiling with the ground getting closer and the
visibility ahead poorer. It can also be an out if we’re boxed in with thunderstorms
or can’t outrun a squall line; in lieu of flying into such violent conditions,
especially VFR. In any event, landing in fields can be a far better alternative. Just
don’t rush; stay cool and fly the airplane!
Where Is the Wind?
Flying VFR, a pilot must be constantly aware of the wind, where it’s coming
from, and how fast. In mountains, it’s helpful to realize that there will be more
cloud on the upwind side of a ridge, and it doesn’t have to be a steep ridge. Even a
gently sloping hill will give enough lift to the air to cause clouds. This somewhat
reviews part of Chapter 11 , but we feel it’s worth it.
On the downwind side, there will be downdrafts, and if the wind is strong,
they’ll also be strong and turbulent. One needs to be flying in clear air, with good
visibility, when wrestling downdrafts, so fly a fair distance from the mountain on
the downwind side, where it will be clear or the ceiling will be higher. The
airplane’s altitude should be above that of the range, if clouds will allow. The
worst downdraft spillage on the downwind side of a ridge will occur at or below
the level of the mountains or perhaps a little higher than the ridge, but not by
much.
There are areas where winds converge. This can cause turbulence and,
sometimes, enough lifting to make clouds. If the wind is flowing down a valley
and there’s a ridge in the valley, the wind will be split as it goes around this ridge.
On the downwind side, the wind comes back together again, pushing against
itself, creating an area of convergence and vortex. We have to consider those cuts
in mountains, ridges oriented in different directions, peaks, and valleys all cause
moving air to tumble and eddy in very irregular ways that are difficult to
visualize. Wind coming down one valley and flowing into another will give
turbulence and convergence. Caution is called for in mountainous areas,
especially in areas where the mountains are arranged in hodgepodge fashion and
not neatly lined up. There can be areas of cloud in unexpected locations because
of mountain irregularities.
Near Cities
If one is approaching an industrial area, town or city, a detour around the upwind
side will give better visibility. This rule will often apply to bodies of water, too,
where a light wind can give more fog and lower visibility on the downwind side.
Summertime
While summer is a nice time to fly, it sometimes brings serious visibility problems
to the VFR pilot. The sky may be cloudless, but the summer haze makes a crosscountry flight by map reading a difficult chore. This is an especially good time to
be on the upwind side of cities, because the polluted air mixes with the haze and
makes the visibility much worse. Even if using an electronic sectional chart
display, with moving-map position of our aircraft, we have to look out and relate
the map to what’s down on the ground, searching for places we might go should
an engine failure or similar fix suddenly occur. And, of course, hazy weather
makes spotting other aircraft more of a challenge.
An inversion causes all this, where the temperature aloft suddenly gets
warmer. The hazy air can rise no higher than this altitude where the temperature
increases.
Climbing, we come out of the mass of glop and find ourselves in clean, clear
air with miles and miles of visibility. Looking down, however, we see almost
nothing, and navigating is difficult. An occasional river glints through the smaze,
the white ribbon of a highway, a piece of a mountain. It’s all difficult to put
together in the jigsaw puzzle of map reading. If we are VOR, ADF, or GPS
equipped—especially with a GPS sectional chart moving-map display—we can
use this equipment for navigation and, by looking at the occasional clues below,
know where we are, where that nearest airport is, and what the countryside really
is like, should we need to descend or find a place to quickly land, say from an
engine failure or similar dire mess. Without these navigation systems helping us,
it’s a job of super concentration, and often it’s worthwhile to swallow pride and
fly a slightly longer course to follow a visible highway or other geographical
feature.
Thunderstorms and VFR
Summer brings thunderstorms, and depending on where we are flying, reduced
visibility in summer’s haze makes them difficult to see. On top of the haze level,
the big cauliflower clouds can be seen clearly and are easily avoided. Down low,
in the smaze, one doesn’t know if the bad visibility is smaze or darkness from a
nearby thunderstorm. Flying high, above the haze and ducking thunderstorms, a
pilot needs to also watch below, because clouds may sneak underneath us if we’re
close to a storm.
To avoid thunderstorms, we need to see them. For VFR flight, this usually
means visually, but radar and lightning detection equipment can help, as long as
we remember our VFR limitations. This process begins before takeoff, during our
weather briefing. With all the sources of NEXRAD, we can usually get some sort
of look at thunderstorm activity, so we can plan our VFR far around any
convective weather areas. If we are without radar, a call to the FSS can give us
radar data, as well as Convective SIGMETs. We need to ask plainly for what their
radar is showing, as a supplement to the broader look by Convective SIGMETs,
but once we have this data and are underway, we’re remembering data that is now
untimely. We use this information for avoiding the areas, not for squiggling
through them. Once airborne, Flight Watch, FSS, or ATC may be able to help us
with radar data. However, ATC may not always be able to do so, because of traffic
demands, and Flight Watch is again our vision from their words, rather than a
direct picture. So we don’t take off planning to fly through thunderstorm areas by
getting help from the ground. If we do have NEXRAD, lightning detection, and/or
airborne radar, because we’re VFR, we use this information to totally avoid the
area.
Thunderstorms, at best, are things to avoid. This is especially true for the VFR
pilot. A good look at the weather before flight will show if thunderstorms are
going to be of the air-mass types or ones caused by frontal activity, and therefore,
how to plan around them. Air-mass storms are scattered enough to tour around,
staying in the clear. If they are frontal storms, the VFR pilot’s place is on the
ground!
Ducking around thunderstorms means staying out of them, and it also means
giving them a wide berth. Turbulence outside a storm can be as rough as that
inside. There’s also danger of hail falling from the high, overhanging, anvil
portion of the cloud into clear air. A general rule is not to fly over lower clouds or
under higher clouds in the immediate vicinity of thunderstorms.
While weaving around, it’s best to keep working upwind of the storm, because
most action is on the downwind portion. Also, an eventual return to course will be
shorter with faster ground speed. Compass headings should be noted: knowing the
time on various headings is a help in guesstimating how far off course one may be
going and which way. Obviously, a GPS makes this scenario a lot easier, but we
emphasize still keeping this mental picture of things. This is our redundant system
when depending on electronics.
An important point about headings is that if one seems forced to keep working
in one direction, say southwest, and is unable to work back northwest because of
storms, it’s obvious that one is making a big end run. This means that the storms
are pretty well lined up, and there isn’t any clear path on the desired course. It
may be a front, a prefrontal line squall developing, or a bunch of air-mass
thunderstorms that have lined up in a pseudo-front. It’s time to land, or turn
around and go back.
A pilot must consider that the storms being circumnavigated may be right over
the destination. If so, it may be necessary to go elsewhere or fly around out in the
clear until the storm drifts away. This means there must be enough fuel on board
and daylight remaining.
Flying VFR at night around thunderstorms isn’t a recommended procedure; it
is very difficult to see where the clouds are located, and in early evening, the
storms are probably at their worst, with the clouds more extensive. Even with
NEXRAD, we need remember that what’s on radar is rain. It does not show
surrounding clouds, and we will not see them in the dark of night, until suddenly
everything disappears, and we are on instruments! One simply should not be out
there unless instrument-qualified; it’s an instrument environment.
A point to remember about air-mass thunderstorms is that they occur mostly in
the afternoon. If a pilot gets an early-morning start, it’s possible to avoid a lot of
air-mass thunderstorm activity. Depending on our journey’s length, we may be
able to reach the destination before afternoon storms have built up and covered a
wide area that is difficult to get through.
There is much more to be said about thunderstorms, which we’ll do in the
chapter on thunderstorms. But right here, while talking about VFR, these points
are important, and the most important of them is to stay in the clear, always
having a wide avenue handy for hasty retreat.
VFR on Top
Flying VFR doesn’t mean one has to stay under clouds. If there are scattered
clouds with a top that’s not too high, it’s better to be on top in clear air than down
in smazy air worrying along in reduced visibility. It’s also more pleasant, because
the air is smooth and cool.
We must be certain, however, that those scattered clouds stay scattered and
don’t become broken or overcast. A non–instrument qualified pilot must be able
to come down without going through clouds.
A good study of weather before takeoff can assure the pilot that the flight isn’t
toward frontal conditions or into mountainous areas, where clouds tend to be
broken and at times overcast instead of scattered with higher tops. Also, over
higher terrain, cloud tops can rise, and suddenly one is stuck with cloud tops just
below our cruise altitude, and the inability or prudence of climbing higher due to
aircraft performance or pilot physiological limits. Even if we are legal to file an
IFR flight plan, if the sky is cold enough, we’ll be entering IFR into ice potential;
as discussed more in the chapter on icing, if the temperatures are freezing to the
ground or our minimum en route altitude, we’re stuck in any ice without potential
escape. VFR on top, for the non–IFR rated pilot, becomes a trapped situation
when issues occur, such as an engine problem, something starts smoking, and so
forth. However, all said and done, if the clouds are scattered, there’s no sense in
sitting down low working and worrying unnecessarily.
VFR on top, in northwestern Montana. Nice VFR at 11,500 feet, but the 2,500foot valley floor, with landable fields and some airports, was fogged in. That
lasted about 60 miles, or a half hour of flying; it was clear either side into skinny,
mostly treed valleys. There were a couple of choices; one was turning back and
waiting for it to clear, but with the concern that the dissipating fog would provide
lifted moisture from the warming day, risking a cumulus-clogged valley. The other
choice was to go, and for a half hour hope the engine didn’t quit—or that
anything else would happen that required a quick landing. What is your decision?
(PHOTO BY ROBERT O. BUCK)
Using Electronics When VFR
Today, most airplanes are well equipped as to communications, navigation and
weather data, much of which comes from some sort of GPS-based navigation
system, even if simply pocket sized and portable. So now, a simply equipped
VFR-aircraft can, with a good aircraft radio, transponder and GPS unit offering
data-link capability, have excellent communication, navigation and weather
information ability, far in excess of any earlier generation jet aircraft; even if a 70
mile per hour Piper Cub. The VFR pilot can use this equipment as an extremely
accurate aid to navigation, communicate with ATC, and of course, if so equipped
with data link, keep an eye on the weather—be it text reports or digital images;
and all on a simple VFR flight. A big benefit of this data-link weather information
is through images of radar and satellite, as well as station reports and warning
information, the VFR pilot now has a top-shelf “big-picture” look at their flight.
This allows end-runs of weather which increases utility of general aviation, even
if just VFR. This is also good training for the future when working towards an
instrument rating.
There are three basic parts to this related instrument capability. One is
knowing how to fly by instruments, keeping the airplane under control without
outside visual reference. The second part is navigation, handling radio
communications for ATC purposes, and obtaining weather information. The third,
if our airplane is equipped with high-end electronics is managing all these systems
for a functional flight.
The pilot who cannot fly instruments can nevertheless learn and develop
proficiency in navigation, ATC communications, and weather-gathering, and yes,
managing it all, while flying VFR. We practice obtaining weather information by
using the radio to contact Flight Watch and the FSS, listen to HIWAS broadcasts,
as well as to use any data link information we have mentioned above. We learn
where we can get this information, on what frequencies and from which electronic
sources.
We can navigate using our full house of equipment, but we should also use
sectional charts, time and distance, following a track, crossing checkpoints, and
checking speed, using a handheld computer. This teaches us how navigation
works and gives us a sixth-sense for what’s really happening, which is a very
important asset, when using the latest electronic navigation. I (ROB) have seen
this countless times, and also am concerned of a new generation of pilots who
have never been taught navigation without some sort of augmented assistance.
Also, having raw old-school ability makes it non-event when the fancy stuff fails
and we’re far from home.
We should file VFR flight plans and keep in touch with Flight Service Stations
or Flight Watch as mentioned above, which should include obtaining the altimeter
setting of the nearest airport, so height is correct, giving an estimate for
destination, and offering PIREPs of our flight conditions, helping other pilots.
These efforts, along with using our radios for airport altimeter and sky condition
information from ASOS, AWOS, and ATIS broadcasts from airports, by obtaining
the frequencies on our VFR charts, keeps us current with the system in lieu of
flying in isolation through data link information and being disconnected from the
total environment.
If VFR pilots do all these things, they will develop a facility that will be useful
in instrument flying. Practicing and learning VFR will make passing the
instrument test easier and, most important, will mean that when starting to use a
newly acquired instrument ticket, things will be familiar, useful, and safer, sooner.
There’s a lot of value, present and future, in using many IFR procedures while
flying VFR, those within legal bounds, of course.
Without Radio
Pilots without radio can fly VFR and certain types of weather, too. I (RNB) flew
my first seven years without radio of any kind, and this included flights coast to
coast, to Mexico, and to Cuba. That was admittedly in the 1930s, but in 2010,
when the next generation of family flew across the United States and back in a
Cessna 170, had we chosen not to fly into radio-required airspace areas, we could
have gone without radio, having a safe and great time. Ironically, one can have,
through battery-powered GPS and data link, all those benefits of excellent weather
data, radar, satellite, lightning data, and needle-threading navigation without
having radio communication; but that’s hypothetical, and a nicely rigged handheld
radio and headset combination completes the basics; and admittedly is more
prudent in the long run, especially in our ever-increasing air traffic world.
However, if we’re flying old school for some reason, without the availability
of en route information for navigation or communication, the preflight study must
be thorough. In-flight observation of clouds and their type, visibility, wind, and
any other phenomena that may signal changing conditions becomes a constant and
crafty task. Occasionally, it may be necessary to land and check just what the heck
is going on.
But the game is interesting, and a pilot may learn much, so that someday,
when instruments and radio are available, that pilot will be a better weather pilot.
Two points not to be forgotten when flying VFR are the legal minimums and
where one can and cannot go. Like all minimums, they should not be our only
guide; there are times when it isn’t comfortable flying, even though legal
minimums exist. Comfortable means just that. When we are a little tense, wishing
things were better, our psyche may be telling us it’s time to quit, VFR minimums
or not.
While flying VFR, there is a strong responsibility to look for other aircraft.
Often VFR flying is putting us where many IFR aircraft are flying: on top,
sometimes between layers, in traffic areas where instrument approaches may be
coming out of a legal VFR ceiling or departures popping out the tops of clouds
we’re flying over. Some of the IFR pilots, unfortunately, have a mistaken idea that
because they are in the system, on a flight plan, they are protected from all
aircraft. Well, they aren’t protected from VFR traffic in many places, and this puts
a burden on the VFR pilot to keep alert, looking for that other aircraft that could
spoil your day.
Oh! what did we do with that foggy valley in Montana pictured earlier in the
chapter? We went, figuring an emergency landing to a side valley would be slow
and workable in the lighter wing-loaded 170. We cleared the fog in about 20
minutes, and it was clear all the way to our destination of Helena, Montana.
So now, on to the pilot with an instrument rating, a piece of paper that doesn’t
necessarily mean one is a weather pilot because, at first, it’s only a learner’s
permit.
13
About Keeping Proficient Flying
Instruments
We may have an instrument rating, but unless we stay proficient, the rating isn’t
any good. In 1970, when this book was first published, that proficiency was
proving we could adequately hand-fly the aircraft on instruments, as well as
dealing with avionics and navigation. Today, we fly to the same requirements, but
have added the need to demonstrate understanding and management of any
advanced systems. Sometimes called Technically Advanced Aircraft (TAA), this
reflects those sporting combinations of any or all technologies such as Electronic
Flight Instrument Systems (EFIS), GPS-based programmable navigation,
informational displays, advanced autopilots and so forth.
For years, it was a common event to fly IFR without autopilots in single-and
twin-engine aircraft—all hand-flown. If one had an autopilot, it was pretty basic.
The idea of automation that could follow programmed navigation was a rare
concept and limited to aircraft such as the just-introduced Boeing 747. Electronic
displays, as we have today, showing fully programmed routes with autopilots
following both horizontal and vertical path, were still a backroom concept—
especially for light aircraft.
Even airliners had their fair share of hand-flying, and not just takeoffs and
landings. In the 1960s, as a young teenager sitting jumpseat on several Boeing
707 Atlantic crossings, I (ROB) witnessed two with inoperative autopilots. Yes,
the two pilots hand-flew the whole trip of nearly eight hours, swapping off each
half hour; at cruise, where jets are sensitive to fly by hand, the altimeters hardly
budged. As a budding young pilot, it was both humbling and impressive to watch.
However, all is not lost. Even now in 2013 there are still quite a few general
aviation pilots doing a fine job flying instruments without autopilots, or maybe
with just a simple, single-axis one. There are a couple of important aspects that
make this work. First, we should have instrumentation and avionics that are not
complicated or of high workload. Second, we need to be proficient at flying
instruments.
Today, this concept can be overshadowed by all the buzz of technically
advanced aircraft. Yet basic instrument flying teaches golden lessons that will
always serve us well, especially when one suffers failure from an allencompassing electronic flight system. As alluded to in previous chapter, there is
a potential misconception that once one graduates to these highly automated
electronic aircraft, redundancy and reliability allows less necessity for raw flying
ability versus more proficiency with system management. The truth is, they are
both are required, so our work is cut out for us.
One of the biggest challenges to a pilot’s instrument flying proficiency is
overreliance from even basic autopilots. In all fairness, this problem came along
far before technically advanced aircraft, as automatic flight has been around for a
long time. However, we realize today’s programmable technically advanced
systems, when fully used, really demand autopilots; especially if we fly them
single-pilot. The main reason is they defeat rule number one above: they are
complex and demand a high workload. So, we have a conundrum of pilots
needing to stay proficient with hand-flying, while flying aircraft that really should
be flown with automation. There is also a trend toward integrating autopilots and
flight scenarios into initial flight training, instead of solely concentrating on
learning basic flying skills. Our experience shows that learning the flying skills
first, and then applying these to advanced avionics and scenarios, creates a more
well-rounded and capable pilot. Either way, these days a good instrument
proficiency check, especially in technically advanced aircraft, is an integral
process of both adequate (although stellar is better) hand-flying as well as
managing all the electronics, automation, and scenarios.
The reason we need adequate hand-flying skills is simple. Even very reliable
and redundant equipment will break—we just never know when or on whose
watch. To put it bluntly, hand-flown instrument proficiency is the lowest common
denominator of skill that will save our bacon, if we lose the fancy stuff but still
have that bare minimum of standby gyro instruments to keep us upright and bring
us home. Ballistic parachutes, in our opinion, don’t count for this scenario, as they
should not be there to compensate for inadequate pilot ability. So this chapter
discusses keeping pilots as pilots, whether our aircraft is technically advanced or
not, and at the end of a leash that is held by the pilot, not the other way around.
Although we have been discussing instrument flying proficiency, let’s throw
in a little zinger for VFR pilots. When we fly VFR, with technically advanced
aircraft, the programming and monitoring is the same as if we’re flying
instruments; namely, our heads and eyes are inside, taking care of all the system
management and orchestration. If anything, except a minimum of electronics, this
also means we should probably be on an autopilot. So here we go again, we’re not
keeping current with hand-flying, and are not adequately looking outside for other
aircraft and, in the case of VFR, the ground!
So how do we keep sharp? Professional aviation uses simulators to check
pilots at regular intervals, in what most of us know as recurrent training. In
aircraft of complexity, this is imperative. The simulators allow more thorough and
diverse training than one can achieve in a live aircraft, let alone being far safer. It
is also a lot less expensive. Professional pilots are also observed on actual flights
by check pilots, to see how they handle not only flying but also management of
the entire job.
This level of training is finally filtering into personal general aviation,
including light aircraft. It is gratifying to see this discipline in place, especially as
an important compliment to the high-performance, new-generation light aircraft,
and their superb but task-extensive technically advanced instrumentation.
Recurrent training is valid whether we are flying the fanciest equipment or a light
aircraft with good old round-dial, basic instrumentation and navigation ability.
There are many fine organizations that provide this training. Some are
manufacturer-based or aircraft-specific, which is very important in properly
qualifying new customers before they fly away with their shiny new airplanes.
The more advanced the airplane and/or avionics, the more important it is to
consider predelivery training. Then, hopefully, pilots return for regular recurrent
training, with every six months a popular time frame. It’s worth noting this is
often required by insurance companies, for pilots of technically advanced aircraft.
Both check flights and some form of recurrent training are a very smart idea. And
often there are professionals right at home, as well as ways we can stay at top
level and test our own abilities.
Our professional at home is a good flight instructor, and for many pilots a fine
method of staying current; whether self-imposed proficiency or that required by
regulation. Instructors can pick up on undesirable habit patterns and present us
with abnormal events of both aircraft and instrument flying that keep us sharp and
safe. If at all possible, it is very important that we receive our checking and/or
instruction in the actual aircraft we will fly, especially if it is technically advanced
and a custom, retrofitted electronic system. Where in the past round-dials, radios,
and VOR receivers were pretty much just that, the many electronic flight system
vendors and combinations of installation can make each aircraft and its system
unique, in both operation and capability.
Another venue is flying a simulator at a flight school, where again we have the
benefit of an instructor’s mentorship to allow a professional training environment.
These simulators do not have to be highly complex, device-specific arrangements,
although those that are offer a superb environment. There are many excellent
computer-based systems with flat-screen display over instrument panel and
controls; sometimes it’s an understandable matter of cost. Because a great deal of
instrument training deals with orchestrating instrument procedures, flying
approaches, and related abnormal aircraft issues, as well as time to practice handflown operation which also improves our instrument scan, these simulators do a
great job.
At home, computer-based flight simulators offer a lot of similarity to what we
have just mentioned, but of course, without the professional mentorship and
follow-through with the training experience. When we don’t have time or
resources to do actual flying or extensive simulation, these home computer-based
simulators still improve our ability to handle complex ATC procedures and
approaches as well as help us stay proficient with hand-flying and our scan. This
is an especially good combination if our actual flying normally has the autopilot
doing much of the work. In the 1970s, we had a spell of time without much
instrument flying. We used a very simple desktop simulator, with its almost toylike appearance making us skeptical. However, after several hours of flying and
procedures, it really sharpened instrument skills, which was proven when we
finally got back in the air. It was also a lot cheaper than grinding around in a real
airplane. It continued to be helpful during those bad days of Vermont winter, when
we were not flying very often. We can also use some simulation systems to keep
current with minimum IFR currency, as dictated by FARs.
An excellent desktop simulator that is FAA-approved for partial instrument
training and recurrency. Not only is it an excellent way to stay current with handflying skills, but its modern EFIS instrument display allows both initial
familiarization and a refresher to these excellent, yet task-focused, systems.
(PHOTO BY ROBERT O. BUCK. COURTESY OF VERMONT FLIGHT
ACADEMY, INC., AND REDBIRD FLIGHT SIMULATIONS, INC.)
The instrument panel and vision system of an economical yet extremely capable
motion simulator that can provide a large portion of one’s FAA-approved
instrument training. It consists of a little cab with seats for pilot and instructor,
the instruments, controls and vision system offering an excellent instruction
platform with a valid sense of motion. (PHOTO BY ROBERT O. BUCK; AND
COURTESY OF VERMONT FLIGHT ACADEMY, INC., AND REDBIRD
FLIGHT SIMULATIONS, INC.)
In relation to technically advanced aircraft, simulation, or at least electronic
media recurrent training, is a natural fit and arguably required; if not by
regulation, at least by common sense. Being out of currency with these systems
not only reduces their utility, it can create a degraded flight environment, as we
tend to spend excessive time fiddling with electronic system protocol and
management, because we’re rusty with the task. This keeps us heads-down in the
cockpit, with all the commensurate risks, not the least of which can be loss of our
aircraft’s primary control. This world of media training is taking serious hold,
even to the extent that many professional aviation operations, including airlines,
are going the way of home computer–based material to cover ground school
aspects of training, leaving simulation of procedures and flying as the majority of
their in-house training.
Of course, this media need not be limited to just aircraft training. There are
many diverse media tutorials that can keep us sharp with things such as GPS
navigation, ATC practices, and yes, weather.
The ultimate of simulation. A Boeing 777 simulator, it’s an identical cockpit
replica, with perfect duplication of operation, including extremely realistic
outside vision and motion. These simulators allow all training from first lesson to
type-rating, and the pilot’s initial airplane flight on a revenue trip with a checkCaptain. In this image, as the pilots set up their instruments and systems, the
instructor—in this case a qualified captain—prepares his challenges. (PHOTO
BY ROBERT O. BUCK)
Practice
The first thing to consider is how we fly every day. We need to fly precisely,
practicing in good weather or bad. If we fly as though an FAA inspector was
looking over our shoulders, we’ll fight off complacency and sloppiness.
Surprisingly, trying to fly the best possible way will finally become our normal
flying character, making us better pilots all the time.
This means holding altitudes and headings as closely as possible, flying
precise airspeeds in climb and descent, and making corrections smoothly and
exactly. If we do these things, they become a habit.
An important part of this is to use an instrument approach as much as
possible, every time there’s one available for the runway we’re landing on, good
weather or bad. The more practice, the better. In today’s world of technically
advanced aircraft, we’ll alternate between flying them manually and automated.
That way, we stay sharp not only with hand-flown approaches, but also with the
complexities of programming and monitoring the automatic ones. The reason for
this is obvious—the autopilot is going to take us where it’s told to go, and being
close to the ground gives us little if any time to deal with mistakes and
quandaries.
We should also throw in a missed approach now and then, as we don’t often
do them, but when they are needed we’re low and slow and must quickly
transition to climb; the margins are slim. Statistics show missed approaches, along
with takeoffs and landings, to be a very weak area of flying skills—in other
words, too many accidents occur in these areas. That says something about
needing to keep basic flying skills sharp, because these phases of flight are usually
hand-flown.
These practice approaches, depending on our currency and ability, are usually
best flown in weather that is better than actual IFR minimums. However, we play
the game as if it were real, including all the normal approach review, briefings,
and system setup, then follow all the appropriate protocol. Finally, in the real
world of low weather, if we have the equipment, we’ll fly that approach coupled
to the autopilot, allowing full attention to monitor the whole event and with the
confidence that if we must assume manual control, it will be workable and safe. It
is also important to sneak up on actual minimums, setting them higher for a
variety of reasons, such as being a new pilot, not current, having new equipment,
or maybe not feeling so sharp that day. However, when we practice approaches in
better weather as mentioned above, we should fly the approaches to actual
minimums. This helps a neophyte lower those higher minimums, but either way,
if we’re stuck with the real deal, it’s a more doable task. As a side note, when an
airline captain first checks out in the position, or in a new aircraft, regulations
require instrument minimums to be increased, sometimes for as long as 100
hours, depending on the type of approach.
On one side, we tout the necessity of manual practice, but on the other we say
doing so in technically advanced airplane can be extremely demanding. Fiddling
with buttons and knobs while hand-flying is not a good combination. One way to
help this issue is to use a spotter pilot. Obviously this is a no-brainer, and is also
regulation, if we practice IFR by flying “under the hood,” which duplicates
instrument conditions. Another help is to have as much programming as possible
taken care of before takeoff, or if in the air, as a prelude to disconnecting the
autopilot for the practice session. If at any time in our make-believe world real
problems occur, we should immediately discontinue the training and revert to
normal operation. However, in the real world, if we have a real problem that
compromises airplane or equipment, we need to advise ATC of our condition,
maybe request things like vectors, direct routings, a diversion to better weather, or
even land to get the equipment fixed or at least wait for better situation.
When flying ILS approaches on a VFR basis, it’s interesting to see where the
ILS takes us. One learns about bends in both localizer and glideslope when flying
an ILS, or quirks of other approaches, and what sort of terrain they thread us
through. It gives us a chance to see what various altitudes and terrain clearances
look like along the approach path. We can learn how far “off course” it’s possible
to be at minimum altitude in order to have enough room to turn and safely make it
to the runway—without aerobatic maneuvers close to the ground. And if we want
to really see what a circling approach is like in reference to terrain, try one at
minimums when the airport is clear and quiet; it can be an eye-opener.
GPS approaches tend to be pragmatically consistent, whereas ILSs and VORs
act in different ways. They have their own characteristic bends; they have
personality. Also, glideslopes are not good all the way to the ground. Usually,
their signals become useless at some altitude near 100 feet. I’ve found that this
altitude varies with individual glideslopes; some are good down to 80 feet, while
others “come apart” at 150 feet. Category II and III runways obviously have
excellent ILSs, but that is predicated on having no aircraft within the ILS critical
area. When conditions are better than Cat II/III, aircraft usually taxi closer to the
runway, which can add interference to lower ILS accuracy; so, if we’re practicing
a low approach in better weather, that ILS may wander or become inaccurate
before we reach minimums. So while practicing ILS approaches, we can see
where the glideslopes, especially at runways we frequently use lose their
accuracy. All this can be handy knowledge on some stormy night when we really
have to shoot a tough one. It’s good to know the peculiarities of each approach we
normally use.
Proficiency is a matter of practice, and that is a matter of doing. We really
should practice these situations in all phases of flight; not just approaches,
takeoffs, landings and go-arounds, but also climbs and descents, where we need
be dynamic in three dimensions, versus just grinding along straight and level.
With automation in general aviation at levels that mirror large aircraft, these
different venues of flying are closer than ever before in emulating the quandary of
staying proficient. In professional flying, staying sharp with “stick and rudder”
skills isn’t easy, with occasional hand-flying and 6-month simulator checks the
only way we can stay sharp. Recent statistics of a professional flight operation
showed the average hand-flown time per flight of literally just minutes; we’ll
brashly say this is typical throughout the whole industry, including personal
technically advanced aircraft! With today’s ultra-long haul airline flights having
multiple crews for rest regulations, just staying legal with landing currency is a
big problem; trips to the simulator just to make three take offs and landings for
maintaining currency are not uncommon.
The pilots we’ve seen that seem to have trouble on instrument checks are the
ones who get in the habit of doing only the necessary flying and no more. If it’s
VFR, they just go in and land. They don’t make use of flying’s opportunities.
We’ve seen pilots have trouble and then, when awakened by the jolt of a down
check, get to work and come back to top-level proficiency. Generally, one jolt
lasts a lifetime. It not only raises the ugly idea that maybe we shouldn’t be doing
this flying routine, but even worse, if we’re professional pilots, we could find
ourselves without work. It’s also a real injury to one’s pride.
Managing Flying Workload
When flying instruments, especially when hand-flying, we’re balancing a lot of
balls. The ability to fly the airplane, manage all the gadgets, and deal with
weather, ATC, and so forth can be overwhelming. Throw in an abnormal system
problem, and things can turn into a real goat-roping event. A real trick to relieving
some of this chaos is not to press ourselves to function faster with more
multitasking, but instead to prioritize what’s important and what we can put aside
for later, or maybe throw out altogether. This is not knowledge that can be simply
taught; it comes from good instruction, practice, and experience.
When we get overstressed, it is amazing the stuff we’ll do while at the same
time having no clue we are doing it. Video cameras in simulators were a humbling
but effective concept, where the lesson was to load up the crew and see what they
did. We’d swear we didn’t do this or that, but by gosh, we did! Our career
dovetailed with development of what was called Line-Orientated Flight Training
(LOFT ), which is also scenario training. It’s not just about learning to do things
related to flying, but also helps us learn about ourselves and how we function in
the flying environment. This, of course, was an adjunct for pilots who’d spent
many years first developing good basic flying habits.
In due respect, a fair portion of old-timers kind of figured this out long before
LOFT. In 1969, while seeking an instrument rating and well before my aviation
career, I (ROB) met a marvelous man named Charlie Gress. Retired from Douglas
Aircraft, he had run the instrument training that kept the Douglas flight
department up to snuff. Charlie’s retirement job was operating a little instrument
flying school at Santa Monica Airport in California. However, he did not use
airplanes; instead, he used two WWII–era Link Trainers. Their stubby and boxy
little wooden fuselages, with one seat covered by a wooden hood, sat about four
feet off the ground on a pedestal in which pneumatic bellows hissed the ersatz
motion of these humbling little trainers. With a set of real aircraft instruments,
controls, and lighting from the Link’s time period, you sat in the aroma of wood,
glue, varnish, leather, and oil for mechanisms, feeling about 1943. This was no
toy operation; these things trained an era of superb aviators, and Charlie was an
old-school master with old-school expectations.
We started with the Link sporting a basic panel of turn and bank, compass,
ADF, and so forth, practicing standard instrument maneuvers. Then we’d go to
the fancy Link with the artificial horizon, directional gyro, VOR with ILS, and
yes, another well-used ADF. Sadly, we just missed the era of low-frequency, range
navigation. And before a session was over, to that aroma of wood, leather, and oil,
we added a lot of sweat.
So in my aviation life the concept of reducing cockpit chaos, by prioritization
of what’s important, began from a few of Charlie’s rules. One was not to write
down any clearances and the same for figuring holding patterns: listen, think and
remember. Another insisted anything requiring timing to navigation was done in
our heads, remembering basics like a 360° standard turn took two minutes,
holding legs were one minute, and we cruised two miles per minute. You threw in
descent rates for altitude clearances. Lastly, the big one was to never, but never,
distract ourselves by picking up that magnificent WWII–style microphone and
talk during climb, descents, or turns. He usually arranged things so we’d not have
long periods of time from his mock ATC commands and our communication, but
the idea was to fly the airplane first, navigate second, and talk third.
As a side note, if you tried sneaking that mic off its hook before you were
level, somehow Charlie knew. His monotone and disciplining voice would say:
“Put the microphone down and flyyyy the airplane!” How he knew remains a
mystery, but more importantly, Charlie taught as much confidence as he did the
gift of old-school instrument flying basics.
Obviously, in these later years, especially with boom mics and good
autopilots, we can do a fair amount more in other than straight and level flight,
but certainly not without keeping an eye on those primary flight instruments;
autopilot or not. Also, in reality to today’s complex ATC world, it’s really
necessary to write down and understand all clearances; but Charlie taught one to
think! (And those years with Charlie were over forty years ago, when young
enough to have a memory.) Still, it’s important to focus on seeing our airplane
capture an altitude, course, complete a turn, or confirm a mode-capture on an
EFIS display, and so forth, before fiddling with something or worrying about
ATC. This is sometimes difficult when there is something creating an issue that
can suck our eyes and brains away from basic flying. Throughout a fortunate and
safe aviation career, whenever things got hairy, you could hear Charlie saying
“Flyyyy the airplane.” Even in fancy equipped, high-performance airplanes, his
lessons were never outdated.
Self-Checking
We are always interested in how good we are, and what sort of situation we can
handle. Well, in the absence of a check pilot, let’s be our own check pilot. And
yes, this is hand-flying!
Because we will be flying under the hood, the first thing we need is someone
to ride along who will look out for traffic. That person must also be able to
recover the airplane, if we don’t fly instruments so well and it gets out of control.
Two pilot friends can ride for each other and learn a lot in the process.
Once in the air and at a good altitude, say 4,000 feet or above, put on the hood
that prevents us from looking outside. We’ll fly these following exercises on the
primary flight group: needle-ball or turn coordinator, airspeed, VSI, and a wet
compass. If our backup gyro is an attitude indicator that will obviously be what
we’ll use, but the rest is the same except many glass cockpits don’t have a VSI for
backup. That’s where we need to know what attitude and power setting gives “X”
speed and rate of climb or descent, or count seconds while reading the altimeter.
The exercises should be done without any appreciable altitude loss,
overshooting or undershooting altitudes when descent or climb is called for, nor
any great airspeed fluctuations. Any indication that we don’t have the airplane
under control or are unable to keep it from stalling or exceeding high-speed
limits, means instruction and practice are needed before we do any instrument
flying. Remember, we must be able to fly the lowest common denominator of
instrumentation for an otherwise perfectly good airplane. All the good stuff could
quit on our next instrument flight. So here we go: round-dial ADI and DG/HSIs
get covered; glass panels go dark. We’re off to the rodeo!
Here are the test maneuvers, under the hood, primary flight group:
1. Straight and level for 5 minutes.
2. Climb at 300 feet per minute, airspeed 50 percent above stall. Climb like this
for 1,000 feet. Level off at an exact altitude. Then descend at 500 feet per
minute, same airspeed, for 1,000 feet and level off at the altitude where we
started the original climb.
3. Do a straight-ahead stall and recovery. A real stall! Not an approach to stall,
but one that makes it shudder and shake and want to duck a wing.
4. A standard rate turn to right for 360°. Maintain altitude within 50 feet. Roll
into one-needle-width turn to left for 360°. Hold altitude.
5. Stall from 30° banked turn.
6. Establish three-needle-width—or similar off the turn coordinator 1 turning to
the left for 360°. Keep turning and start descent, allowing airspeed to build up
to 30 percent above cruise indicated airspeed IAS. (Don’t exceed any limits.)
Descend 1,000 feet. Stop descent, level off, and come out of turn.
7. Following the above, immediately roll into three-needle-width turn to right.
Do one 360° turn and then climb in the turn at 70 percent above stall lAS for
1,000 feet. Level off and stop turn.
If we can do all these things neatly and with precision, being a master of the
situation all the time, we’re a pretty good instrument pilot.
With Full Instruments
Now uncover the DG and horizon, reignite the glass panels and fly with a full
panel. However, this is still all hand-flown—no autopilot, flight director, or
augmenting indications on a PFD. Now we do the following exercises. They are
to show the precision demanded when flying in a traffic area and executing an
approach and go-around (missed approach). They should be done with great
exactness: airspeeds within a few knots, altitudes exact and not varying over 50
feet, headings hit on roll-out within 3°. Here we go:
1. Straight and level. Hold exact heading and IAS.
2. Reduce speed to 50 percent above stall. No altitude gain or loss.
3. Reduce speed to 40 percent above stall. Turn 45° to right. No altitude change
and hit new heading within 3° on roll-out.
4. Maintain the above speed and descend at 300 feet per minute. Turn left 170°.
If we have a retractable landing gear, lower it.
5. Level off, lower flaps to landing configuration, reduce to approach speed.
Hold this for 2 minutes.
6. In the above configuration, descend at 500 feet per minute to a preselected
altitude 1,000 feet below.
7. At that altitude, do a go-around. (Tune a VOR to a new station, set in a
different radial, select a waypoint, or do some other demanding task.) Turn
left 90° as you do. Establish climb speed and clean up gear and flaps. Climb
1,000 feet and level off.
These exercise maneuvers are to check our sharpness. They aren’t an
instrument pilot’s final exam. They are simply something to go back to now and
then for an appraisal. The degree of precision obtained tells us our capability.
The maneuvers on the primary group are really designed to make certain we
can keep out of, or recover from, a spiral condition with increasing airspeed and
recover from a stall.
We can vary these maneuvers and design more. The basic thing in the fullpanel maneuvers is to try and load ourselves up with all the things that might be
required, and see whether they can be done with the precision demanded by the
ATC system and, of course, safely. This means one needs the ability to change
speeds while climbing or descending, turn to headings, lower flaps and gear,
adjust rates of climb or descent, and hit altitudes and headings exactly. There’s
also a requirement to remember these altitudes and headings and keep them after
leveling off.
One could do all these things and toss in an extra job of consulting charts and
worrying about carburetor heat, as well as talking on the radio. It can be quite a
load, and we’d better face the fact and be prepared to handle it, because that’s the
kind of load one can encounter in the system. It is a handful for a neophyte
instrument pilot, especially alone and without autopilot.
We should check ourselves periodically—every few months. An honest selfappraisal is often more severe than a check pilot’s. This isn’t the place to kid
ourselves; if we’re not up to snuff, we should practice more, or go back for help
from a professional instructor, or both.
A Clever Gift of Flying Basics
When I (ROB) began flying as a teenager, it was in a wonderful little 85
horsepower Cessna 120—for no special reason, named Sam. It had two friendly
seats, a tail wheel, and no flaps. Fun to fly, Sam made one learn to enjoy slipping
an airplane, cruised a decent 100 mph, but was gutless enough to build humility at
a short airport. My father also loved the little airplane, reminding him of his
Monocoupe during the 1930’s. In his eyes, the only drawback was a basic VHF
radio with VOR navigation. Such led him to emphatically tell me it was okay to
talk on the radio when I had to, but leave that “Omni,” as he called it, alone until
“later on.” Vague time frame, but I liked to fly—stick and rudder stuff—so didn’t
think much about it.
After my ever-patient and superb instructor, Jim Frankenfield, left me free to
roam beyond local solo flights, I began exploring either side of the Delaware
River, from Van Sant airport in eastern Pennsylvania. I was to use a map, and if
lost, figure it out or go land somewhere—even if a farmer’s field, before running
out of gas or getting stuck in bad weather. Pretty straightforward; I think Jim and
my father were in cahoots.
Yes, I occasionally fiddled with the VOR—probably just because my father
said not to touch it—but mostly ignored it, because flying that nice handling 120
was more fun. What was happening, however, without gadgets to fiddle with, I
looked out the window at weather, terrain, a place to go if the engine quit, and for
other airplanes. It was shooting landings—sometimes of fair crosswind at Van
Sant’s single grass runway—and don’t spin-in circling everyone’s home. Later
cross country trips kept me thinking about where north was, how much fuel was
needed, and what’s going on with the airplane and engine.
Of course “Omni” came into the picture, as did different airplanes, a diversity
of flying, and the process of gaining pilot ratings, including that instrument one.
We also said a sad goodbye to Sam, as a fully equipped Cessna 182 came along
that was festooned with the works, except for one thing—an autopilot. The
instruments were plenty, capable, but simple round ones. This Cessna was also a
marvelous airplane, and I flew it hundreds of hours, crossing the country three
times, and like so many others of the era didn’t think too much about not having
an autopilot.
Decades later, just after retiring from the flying career, my father and I were
talking about—what else—airplanes. He asked me what was most memorable in
my career. The best flying had been with Air North’s Twin Otters out of
Burlington, Vermont, then on the Shuttle out of La Guardia in New York; a
favorite was hand-flying between Washington or Boston in the 727, during the
quieter times of a day. That Boeing was fun to fly, the weather diverse, and the
Shuttle was a fly’n operation! We talked about flying the later “electric-jets,” and
how despite the fancy instruments you always had the itch to know if the airplane
was working okay and aimed in the right direction. And that retirement flight’s
last landing, kicking out the crab from the crosswind on 22L at JFK; I’d felt a
flashback to Sam at Van Sant, and it was a fine landing. Then he said: “You
remember when I told you not to use the Omni in Sam, and there was no autopilot
in the 182?” He and Jim had a plan and it was a very clever one.
1 . Three-needle-widths refers to older Turn and Bank instruments originally
used by first author, in 1930’s. One needle-width was a standard rate turn of 3
° per second. Three widths is three times standard rate or 9 ° per second/40
seconds for a 360° turn. For use of standby-ADI’s we recommend at least a 45
° bank for this maneuver.
14
Thoughts on Flying Technically
Advanced Aircraft
Technically advanced aircraft (TAA ) are the new high bar for weather flying, and
they are marvelous. However, to the uninitiated or poorly prepared, these aircraft
and systems can be overwhelming. It’s not just about learning how to operate the
equipment; it’s also about learning how we merge their huge quantity of
information into our flying, and how these systems affect the pilot. So we need to
make a disciplined investment of time and patience in learning how to fully use
whatever flight instrumentation and automation we have, and do so before trying
to use them in-flight!
The learning curve can be steep, requiring our restraint as we climb that hill.
This means that even after learning the buttons and programming, we tread
carefully, developing experience in their use. Maybe it means more time with an
instructor or simulator, even flying conservative day-VFR for a bit, despite the
temptation to jump right into instrument flying—the home court where these
technologies shine.
So we take the time to learn our new equipment, but we’ll tell you flat out this
book is not going to broach that huge subject; it’s too big, too rapidly changing,
and frankly isn’t within the context of the book. Instead, our comments of this
chapter are from personal use, as well as operational concepts that developed in
early use of these systems, which became standards of procedure or helpful
technique. There are many fine publications and media tutorials on operating
electronic flight systems and automation—we recommend all you can get your
hands on—but the most important are those specific to the equipment you use.
This point is really important, especially with older aircraft retrofitted with
electronic flight systems; each one can have minutely different but operationally
influential variations.
One publication that we consider to be highly recommended reading, and
certainly neutral ground, is the FAA’s Advanced Avionics Handbook (FAA-H80836 ). There is a quote from the book that we feel is very worthy, its subject related
to a fair amount of TAA incidents and accidents, in both personal and
professional flying: “Many studies have demonstrated a natural tendency for
pilots to sometimes drift out of the loop when placed in the passive role of
supervising an FMS/ RNAV and autopilot.” 1 We can plug in any combination of
available technically advanced flight systems for FMS/RNAV, 2 so either way it’s
the same idea.
This “in the loop” situation is a big deal in the world of technically advanced
aircraft. With these aircraft, we add a lot of stuff to the “loop,” both in system
operation and information output. This increases the risk of becoming passive in a
couple of dangerous areas. One towards less monitoring of basic flight
parameters, due to excessive programming and function innate to these systems,
which keeps us heads-down, hence not watching what the airplane is doing and
where it is going. The other issue is because of this excessive programming and
monitoring, we rely on autopilots; hence hand-flying skills deteriorate.
When electronic flight instrumentation, programmed navigation, and
advanced automation were synced together and first introduced with the airlines
(and probably where the term “glass cockpit” began) professional training was
necessary and helped, but there was a lot the industry didn’t know about the
interface between pilot, airplane, and the glass cockpit; there was a fair amount of
on-the-job training. Fortunately, having two experienced pilots with old-school
flying sense usually meant someone finally said: “I’ll fly and you fiddle with the
thing.” Either way, there was enough excitement to convince everyone that this
new equipment was great, but could be distracting in ways never before
experienced. Disciplined flying had a new meaning!
Single-Pilot Operation in a Two-Pilot World
Whether in a single or two-pilot aircraft, the concept of operating a technically
advanced cockpit is pretty much the same, and depending on how fancy your
equipment is, technology has tightened the gap between small and large aircraft
systems. The obvious benefit of a two-pilot operation is that extra set of eyes,
which supposedly ensures someone is always tending to flying basics, including
looking outside in visual conditions, but also very important is having redundancy
for just about everything going on in the cockpit. Another more subtle advantage
of a two-pilot cockpit is being able to observe how a multitude of pilots—and
personalities—interact with the electronics, programming, and automation. With a
good crew relationship, constructive suggestions or warnings are welcome and
frankly necessary.
The single pilot of a general aviation TAA operation obviously has their work
cut out for them, and we admire the majority who do it well. No matter how you
skin the fruit, an autopilot does not totally make up for a second pilot, so in
single-pilot operation we need to keep our minds thinking and eyes busy—and
not fixated for very long. That’s hard to do with longer tasks, such as extensive
programming of technically advanced flight systems. This increases the reliance
on autopilots, again reducing those hand-flying skills. And redundancy? There is
none, so we better get it right.
Dependence on Augmented Indications
As well as autopilots, some electronic flight instrument systems have a lot of
augmenting indications in the instruments to assist the pilot with flight guidance.
We like to call them “cues.” These cues think for us, by displaying computerprocessed information, derived from raw-data and aircraft inputs, as guidance
cues on an EADI, EHSI, or PFD, as to where we should aim the airplane. Flight
directors, trend indications, course “noodles” showing the projected path of our
airplane, guidance boxes that lead us through a flight path, and so forth, are
superbly done and most helpful. They are really helpful when we’re hand-flying
the airplane, so when they fail, we’re back to basic instrument thinking, and
obviously, if we’ve been overly dependent on cues, we have our hands full.
Now let’s go a step further. We have a total failure of our electronic flight
displays—all of them! Now we have to fly using the standby attitude indicator,
airspeed, altimeter, and compass. Whether it’s an EFIS-equipped Cessna 172 or a
Boeing 777, the situation is pretty much the same. The screens go dark and even
in a simulator training situation, where in theory we can’t get hurt, that moment
can be a dramatic transition period, depending on how sharp we are with basic
instrument flying skills. We can’t dwell on the issue, but instead relax, as we
decide the electronic screens are gone forever. Now it’s fly the standby ADI, using
good old attitude and power (pitch + power = performance), with airspeed,
altitude, and heading just for reference to confirm the airplane is doing what we
want it to do. If we know those attitudes and power settings, it works fine and is
actually kind of fun.
Now, with the above lesson completed, we have a reversed and less traumatic
situation. It’s an experienced analog instrument (round-dial) pilot new to flying a
cockpit with a full electronic flight display, including all the extraneous electronic
indications and cues. That old-school pilot initially tends to avoid all the fancy
stuff by flying “through” all the cues and seeks out the raw data of attitude,
airspeed, altitude, rate of climb, heading, and navigation information. Then they
will add the extra “cue” information when time allows, understanding control of
the aircraft comes first, with the cues and goodies just icing on the cake.
As a side note, learning to read electronically displayed, tape-style instrument
indications, such as airspeed and altimeter, we’ll find we must read the digital
indication, instead of taking a quick glance at the needle position of a round-dial
display. Yes, there are trend and “you’re there” indications, but that’s derived
secondary data; the primary numbers are the real deal, especially if cues or the
whole system goes south. Old-school pilots tend to have their eyes scanning
around in search of some primary indication reference, even if subconsciously.
Thinking again about cues as secondary information, let’s consider, as an
example, the flight director, also mentioned in an earlier chapter; this could be
displayed in an EADI, PFD, or a mechanical, round-dial ADI. We remember from
discussing equipment that the flight director is working off computer-derived
input from primary navigation information, which is most helpful during
instrument approaches. When using the flight director, we should always be taking
a glance at the primary, raw data indications, confirming the flight director is
commanding a flight path that follows the primary navigation; it doesn’t work the
other way around. If there is any question, we ignore the flight director—or turn it
off—and fly the accurate, raw data information.
Electronic Seduction
Sometimes in the cyber world, it seems we risk beginning to function more like a
computer, and less like a visceral, thinking human. A potentially lighthearted
example could be approaching an airport and listening to the ASOS or AWOS
weather, but not looking at the windsock. Then we make a brake-screeching
landing in a good tailwind, because a thermal came through, swapping the wind.
In days past, without ASOS and AWOS, you really had to look at the windsock or
wind-tee at an uncontrolled airport, because few gave wind reports, other than
those where Flight Service Stations provided airport advisory. But today’s world
of taking data from inhuman electronics seems to develop a kind of seduction
away from human thinking.
On the other hand, this could really be serious, such as fixation on and/or
belief in instrument cues or maybe an autopilot operation that is not going as
planned. Rather than referencing raw-data indications, and either redirecting the
autopilot with immediate success, or hand-flying to safety, buttons are pressed
until the airplane loses control or hits the ground. Melodramatic? No, say the
accident records.
When we fly an aircraft with a totally integrated electronic flight system,
sometimes folks don’t fully understand—or remember—that the aircraft flies fine
without this full integration of programmed navigation, autopilot, and EFIS
displays. This situation might be from initial training issues, or insufficient
recurrent training, but can be aided by diversity in using the advanced aircraft’s
systems; either automated or hand-flying, and of course dependent on operational
prudence.
I (ROB) distinctly remember my first jet check-out as a Boeing 737 copilot. A
round-dial panel, nevertheless it had a very advanced autopilot. From the first
simulator lesson, the process was to integrate the flight director operation, which
used functions from the autopilot system. The curriculum was busy, and time for
basic familiarization with the airplane’s flying characteristics was constantly
overshadowed by inputs from the autopilot and flight director. Unless one already
had a similar background, it was a training environment out of a fire hose.
Fortunately, once out of training, many of the captains knew the issues and when
the weather was good, encouraged us to practice hand-flying the “raw” airplane. It
was enjoyable, built confidence and made better pilots.
Sometime later, when checking out in the 767, things had changed. With its
fancy autopilot and now an FMS and electronic instruments, the first simulator
session was configured with just an EADI, EHSI, and VOR/ILS. Then, after some
air work, VOR navigation tracking and an ILS approach, the flight director,
autopilot, and FMS interface were introduced individually. That cemented
understanding of how the various electronics worked together, or could work
independently, building confidence that the airplane was still an airplane, and not
a device. Someone had listened to many suggestions.
There are also varying opinions on training new pilots in this age of
technically advanced aircraft. With the TAA environment, new curriculums at
some flight schools, which have been carefully and professionally created, begin
flying the airplane integrated with all the advanced equipment, as well as
scenario-based training, pretty much right from the first flight. Others, however,
still prefer students’ initial instruction and solos with only basic instruments and
well-developed hand-flying skills, then add new technology after basic flying
foundation is firm. This all circulates around the concern of developing pilots who
are dependent on technically advanced aircraft systems, and lacking basic flying
skills, as well as confidence to use them; they will always be needed, whether in
abnormal situations, or just normal takeoffs, landings and go-around—which
happens to be the most demanding phases of flight and is chalking up too many
accidents.
Another issue relates to pilots who were initially confident and capable handflying pilots, who turned rusty because they became over reliant on an aircraft’s
advanced instrumentation and/or automation. This is something we’ve witnessed
when airlines had mixed-technology fleets of aircraft, as pilots moved from
advanced digital aircraft back to the older analog airplanes; these moves between
different aircraft came from seniority progression allowing moving up in position;
and more pay. We saw it not only as a check-airman, but also feeling the threat,
and fighting it, in our own flying. The simple answer was to hand-fly as much as
we could, and frankly on days off I’d find time to do some good basic general
aviation flying; and personally I’d add some enjoyable sailplane flying.
In technically advanced cockpits, even very capable pilots can get sucked into
fiddling with unnecessary electronic function, and forgetting the basics; it’s
usually worse when we get pressured. In remembering, from previous chapter,
video cameras in simulators, a favored training event was to set the simulated
flight onto an arrival and subsequent ILS approach. When close to the airport, the
instructor issued a parallel runway change. Cleverly, enough time was given to do
a quick review of the approach and set it up through the ILS receiver and EHSI,
but not enough time to sanely set it up through FMS programming. With the plane
usually on autopilot, what happened was two very experienced aviators often
went heads-down into their flight bags for charts (these were the days before
electronic charts) and then heads over the other way to load the FMS. Usually
someone suddenly had their brain light up and mentioned one of them ought to
monitor the flying, but the deed was already done.
The correct answer was, of course, have someone pay attention to monitoring
the airplane flying on autopilot, while the other tuned and identified the ILS, set
the EHSI to ILS mode, and then the approach was flown without FMS interface.
Even the autopilot could couple and fly the approach just fine, not caring if the
FMS was even there; the ILS just talks to the autopilot. It was a heck of a lesson
and really helped tighten things up. Today, with GPS and LNAV/VNAV
approaches, we do have to use programmed information, but the point is most
airplanes can still be flown with controls and throttles only (thrust-levers to
some), and we must always pay attention to the flying first.
An interesting aspect of those distraction exercises was that we’d seen it
numerous times before, well before the days of advanced electronic flight
systems, in high-profile accidents from crews fiddling with systems or problems
and ignoring the flying. Great emphasis was placed on these accidents, and it
improved cockpit discipline. Then, when glass cockpit operations appeared, it was
as though crews were seduced once again by this totally new distraction. We still
have a lot to learn.
There are more and more pilots who have only experienced flying with
technically advanced aircraft; some with a full-house complement. Intrinsically, if
these pilots initially learn with only the basic electronic flight instruments, no cues
or autopilot, it’s similar to learning on round-dial instruments where they fly
maneuvers from the same basic inputs, requiring the same “seat of the pants”
thinking. It also means one becomes skilled with hand-flying. However, whether a
pilot learns with full electronics and autopilots, or in later use becomes
technically advanced dependent, they are equally hooked, and can become overreliant on automation. An example occurs when a problem develops with an
aircraft flying on automation, no matter whether the problem is due to system
failure or pilot-induced error. Those who are automatic-style pilots invariably try
to fix the problem while the airplane stays on automation. More often than not,
things get more screwed up, with situational awareness easily lost. Throw in
automatic throttles with lots of power that cause substantial aircraft pitch
excursions, or on occasion lag in necessary power application which requires
immediate hand-flown thinking and intervention—despite flying in automated
state—we see a myriad of potential “gotchas” developing. This is worth thinking
about as new pilots, some with professional flying in mind, learn to fly; their
training may integrate automation from the beginning, until they are on their own,
supposedly competent and confident to fly both automated and manually .
On the other hand, pilots who have the ability and confidence to hand-fly,
especially with basic flight instrument information, usually disconnect the
autopilot, stay on course, and get everything organized. Then, if not continuing an
approach to landing, they wait until things settle down and attempt to reintroduce
the automation simply and methodically.
There are times when we can solve an automation problem through a quick
selection of a new mode for the autopilot’s operation, and subsequent easy
selection of new target information; airspeed, altitude, heading, etc. It is, however,
a fine line that varies with things like how high we are, phase of flight, and so on.
An important part of this relates to how well one understands the autoflight and
electronic flight system. By the nature of their computerized design, it’s pretty
difficult to learn every little aspect of these systems or remember it if we did. It’s
important to realize that fixing a problem while flying on automation has the same
goal as when we fly manually: keep the airplane flying normally, staying on
course and altitude.
A simple example of fixing a problem while staying on automation could be
the aircraft failing to follow a programmed course or vertical flight path. It might
be easily fixed by selecting the “heading” mode or a nonprogrammed verticalpath mode of the autopilot. We can then use that mode to stay on course from
primary navigation information or control the climb and descent ourselves. Then,
when we have time, patiently try to figure out what’s wrong with the programmed
information.
If that route excursion is near the ground or in hilly terrain, we don’t have
time to fiddle with buttons and knobs or contemplate what’s wrong. Instead, we
take over manually and seamlessly continue the required flight path, using
primary instrument indications. Other critical examples might be autopilot issues,
such as capturing erroneous altitudes due to some strange programming issue or
flying through a preselected altitude. To be aware of these things, it means we
have to know what the airplane is supposed to be doing, and what it is doing.
That’s being “in the loop.” Again, when single-pilot, without that second set of
eyes, we have to discipline ourselves and pay attention, especially when our
autopilot is following programmed lateral and vertical flight paths, and pay
careful attention when the aircraft is supposed to level at an altitude.
When automation fails during an instrument approach, unless we’ve caught
the issue early on and are within parameters, it’s pretty much like a manually
flown approach that gets out of bounds; it’s often better to make a missed
approach. After we’ve completed the miss, we again methodically set up the
approach, and then fly it only when we are ready. With the nature of an approach
being an operation close to the ground, it’s not the time to be racking an aircraft
up, down, back, and forth, trying the save an approach that we can easily try
again.
Programming Thoughts
Compared to aircraft with simpler avionics, preflighting and programming a
technically advanced airplane takes a lot more time. When these systems first
emerged, if we were rushed before departure, the idea was to program enough
information to get airborne and a fair piece down the road. The rest was to be
done in-flight. Whether airline or general aviation, this idea more likely increased
workload, especially if something happened after takeoff that kept us distracted. If
we can, programming our complete route before beginning the flight is a good
idea, especially with an FMS-type system that calculates fuel and time planning.
Unfortunately, some systems, whether from design or capacity, can’t always
program complete flights; if so, we need to do our clerical work in unhurried
times, and especially try to avoid such distracting work during climbs and
descents.
During flight in a true two-pilot, EFIS, FMS, and advanced autoflight
operation, the airplane is flown on autopilot while one pilot programs and the
other monitors the flying. Then, with roles reversed, the other pilot independently
reviews the whole flight plan loading operation, verifying the route. Obviously,
this isn’t much help for a single pilot, with an autopilot not making things equal.
This highlights, again, our need to be on the ball when programming in-flight.
Do we need maps? You bet, and as said before, even if not right in front of us,
we want them close by and easy to fetch.
A big issue when flying single-pilot in a busy cockpit is traffic avoidance;
unfortunately, it usually takes a backseat to everything else. Having collision
avoidance equipment is a very good idea, but it is not the total answer, especially
around busy VFR airports; not all airplanes have transponders, or they may not
have them on. Eyeballs are current and important technology.
Programming electronic flight systems, whether in a single- or two-pilot
operation, demands exact information that is entered totally correct. All numbers,
letters, and spellings must be input with zero error. For example, “GLYDE”
intersection just west of Worchester, Massachusetts, is about 1,210 nautical miles
east-northeast of “GLIDE” intersection, which is just west-northwest of Salina,
Kansas. In a hectic moment or on the tired side of a day … well, the idea is
obvious! There are plenty more examples. That’s why we hear experienced pilots
asking clearance delivery or ATC how to spell certain navigation fixes. If we don’t
catch these mistakes, especially as the airplane turns off-course for Kansas, it
could be a real problem from ATC and/or terrain avoidance issues.
How can we check a routing to see if it goes where it should? Depending on
our system, we might check total programmed mileage, time, or course directions
versus our flight plan. In other words, if a flight-planned 200-mile flight shows
total mileage of 1,200 and six hours flying time, or one segment of the flight goes
in the opposite direction, we’d better look into it; but it’s not always so obvious. If
we can “page through” the route and watch it on our EHSI or MFD, we’ll see
whether the course heads off into the boonies or disconnects between navigation
points. That’s called a “route discontinuity.” If not caught, and we’re asleep at the
wheel (hopefully not literally), the airplane will usually take up the last route’s
heading, flying along until we run out of fuel—or we wake up to the problem.
Again, think traffic and terrain. Now add programming of vertical navigation to
include crossing restriction altitudes. There was one situation where a crew, in
vague state for whatever reason, saw a planned altitude change in their screen and
made the climb without contacting ATC. Brain up and locked; nobody got hurt,
but it didn’t go over so well!
If we use things like Bluetooth-transmitted flight planning, we should still
check our final EFIS routing. As a side note, think about this routine when a
bunch of passengers are babbling or asking questions or an entertainment system
is singing away in our headsets. And do we really need our cellphone in the loop?
This seems a time for restraint, kind requests for quiet, or offering simple crew
tasks to keep passengers busy.
Obviously, when we fly a single-pilot, technically advanced operation; we
have our work cut out for us. We need to be well trained and current, with the
personal discipline not to get lazy, even when tired or hungry. We need to develop
personal systems that give us the best next thing to being in a two-pilot crew, not
just for redundancy but for knowing when things are not up to par and we need to
back-off accordingly. We have to be on the ball, and many do it well.
Summary of Flying Basics in a Technically Advanced World
These are suggested thoughts that have served well for us and many others.
• Learn good basic hand-flying skills.
• Learn good basic hand-flown instrument flying skills, with only primary
instrumentation—mechanical or electronic.
• Then introduce equipment such as programmed navigation, electronic
instrumentation cues, and automation, with an understanding of their operation
and management before attempting to use them in-flight.
• Be capable and current with whatever level of equipment and conditions one
plans to fly.
• Practice hand-flying with regularity, as allowed by one’s ability and the
conditions, especially during climbs, descents and approaches.
• Before any flight, be well prepared and fully organized, with as much
electronic programming completed as possible, before the flight begins.
• If at any time during a flight we are pressing our limits, or feel uncomfortable,
turn around or divert to a safe destination.
• Have the ability to comfortably and safely hand-fly the flight with the lowest
common denominator of instrumentation.
• Throughout any flight, at the least bit of confusion or distraction, always check
the primary flight instrument indications, whether we’re flying with automation
or by hand.
• Always fly the airplane first .
1 . Federal Aviation Administration. Advanced Avionics Handbook, FAA-H-80836 . Washington, D.C.: United States Government Printing Office, 2009, chap.
1, p. 3.
2 . FMS/RNAV: Flight Management System/Area Navigation, which requires
programming and attention away from basic flying of the aircraft.
15
Thunderstorms and Flying Them
Thunderstorms are thunderstorms, and while they may come from different
beginnings, they all turn into the same thing. Once a pilot is in one, he or she
wants to know how to fly through it and come out safely. Even more important,
however, is keeping out of it in the first place; and no matter how old or bold a
pilot may be, the primary thoughts about thunderstorms are concerned with
staying out of them. To stay out of thunderstorms, or fly through if we must, we
should know what thunderstorms really are and the different backgrounds from
which they come.
What Are They?
Simply a cumulonimbus (Cb), thunderstorm, TRW, or T, or whatever one wants to
call it, is a concentrated mass of very unstable air in violent motion up, down, and
sideways. It has strong, gusty winds that generally extend to the ground and make
landing or takeoff difficult or impossible. It has thick clouds, heavy rain, and
sometimes hail. Electrical discharges occur frequently. Some thunderstorms have
tornadoes associated with them, but most don’t. Tornadoes, however, never occur
without thunderstorms. Tornadoes are associated with thunderstorms, but they do
not always come out of the big, bunched-up cumulonimbus clouds with the
highest tops. They often come from much smaller clouds that hang back in a line
from the main storm center. So it’s wise not to duck under or fly through clouds
close to a thunderstorm just because the clouds look smaller and have lower tops.
To make a thunderstorm, we need conditionally unstable air. What’s that and
who cares? Well, it’s air that is stable as long as it doesn’t condense … that’s the
condition. When it does condense, the release of heat in the condensation process
makes the air warmer, and the air wants to go upward. Then more moisture
condenses, more heat is released, and it goes up more. It’s almost like perpetual
motion, and the energy released is tremendous.
The normal places we go for weather information do not tell us the analytics
that determine whether an air mass is conditionally stable or unstable. That is
learned from upper air soundings, such as the previously mentioned Skew-T log-P
information, taken in many places over the country and other factors, then
analyzed by computers at the National Weather Service and Storm Prediction
Center, as well as other sources. The result is the forecasts we use, and if they call
for thunderstorms, it means the air is conditionally unstable or will be, and that’s
all we need to know.
What Is Tough about a Thunderstorm?
What really bothers us most in a thunderstorm is the turbulence. Lightning
discharges are a minor danger, and few airplanes have been knocked down from
lightning. There has been concern of flame going up fuel tank vents and then
igniting a near-empty tank loaded with explosive vapors. Redesign of vent
systems, plus a method of discharging inert gases into the offending vent system
when any ignition occurs, is intended to alleviate the problem.
As for lightning hitting a plane and knocking it down, there is evidence years
back of the previously mentioned and corrected fuel vent issues, but overall, metal
aircraft as well as composite aircraft properly protected do not have catastrophic
issues. This protection to composite aircraft is usually provided by thin metallic
conductive strips or webbings molded into the aircraft skin, which also may
connect metal parts. The protective conductive layer is typical on today’s allweather composite aircraft, which includes the popular single-engine aircraft of
this category, but not all lighter sport aircraft and sailplanes. The process, at times
referred to as bonding, also has used internal wiring between metal parts of
composite aircraft, this being typical of the earliest composite aircraft from
decades ago—those made of wood. Lightning strikes to composite aircraft seem
quite rare, and does not necessarily mean the end. However, in one documented
case, a fiberglass sailplane was struck by lightning, in visual conditions under
cloud, and was basically blown apart. The strike hit the left wing at the aileron
pushrod and exited out the right wingtip area; the transiting “overpressure” from
the electric charge did the rest, destroying wings, controls, and fuselage.
Fortunately, the pilots wore parachutes and exited accordingly, both being okay.
Of thought is that a ballistic parachute would not have helped, as there was no
remaining cohesive structure to support. Again, a very rare event, but interesting.
I (RNB) spent a number of years looking for and flying through thunderstorms
in research work and saw a lot of lightning. Numerous electrical discharges were
experienced, where the aircraft was at one end of the lightning cycle—four in one
day—and the worst damage was a hole about the size of a half-dollar burnt on the
trailing edge of control surfaces. Bigger holes have occurred, but they generally
aren’t caused by lightning. When I had a discharge in a Boeing 707 out of
London, England, a 3-foot-long piece of the black radar nose was torn out. The
lightning actually made a much smaller hole, but the high-speed air from our
forward motion got inside the nose and then tore out the bigger piece. There
wasn’t any special problem, but I dumped fuel and returned to have it fixed
before crossing the Atlantic.
Damage to a Boeing 707 from an electrical discharge, often called a lightning
strike. The point of discharge is small and near the point where fuselage and
radome meet. Large, torn pieces were probably ripped out by airstream wind.
None of this affected the airplane’s flying ability.
Tornadoes
Flying into a tornado, of course, would be catastrophic for an airplane. The winds
are unbelievably violent. But tornadoes can generally be seen if one is outside
cloud, flying VFR. The big hazard is sneaking under thunderstorms at night or
down low in and out of cloud. There is always the chance that while you are
sneaking under clouds near a thunderstorm, a tornado may form, perhaps where
you don’t see it. I (RNB) was lucky one night, in a DC-3, flying from Chicago to
Indianapolis while trying to squirm my way through a line of thunderstorms.
Flying low, as we often did in preradar days, the idea being to stay “contact.”
Ahead I saw a strong glow that turned out to be a large field on fire, probably
started by lightning. But the shock was to see this fire lighting the sky enough to
show a tornado with its scary funnel right on course! I went around it, somewhat
shaken, because what if that handy fire hadn’t lit up the sky! It’s always useful to
have a little luck around.
It is potentially possible that we could pass above a tornado, at an altitude
above the base of the thunderstorms, perhaps 8,000 feet or more. It will be a ride
to remember, but the violently destructive part of the tornado may be missed.
However, by far, the best decision is to avoid the entire area.
In those many years ago of low flying without radar, a friend passed over the
Pittsburgh, Pennsylvania radio-range station in a DC-3 at 8,000 feet while a
tornado was going by on the ground at almost exactly the same place and time. He
didn’t have a bad ride and flew on to Washington, D.C. There have been
numerous cases of this sort, so there’s more than just theoretical evidence that the
violence of a tornado is only in the low levels, but still, this is not reason to make
an assumption and fly in these situations. In those days, there were also a lot of
airplanes lost; why repeat history? Part of the reason for my friend’s good ride was
that he probably missed flying through a cell.
Tornados can potentially come out of both high and low cloud base
convective weather. One wild West Texas summer day in 1967, during a national
soaring competition, a spiny little tornado touched down out of a confused area of
thunderstorms, their bases about 12,000 feet. It was not raining, and just a few
miles to the north the sky was clear. I (ROB) was circling in lift well below base,
when one glider called the tornado. Miraculously, there was only one incident
concerning the ten or more gliders in the same area. That pilot suddenly found
himself in extreme turbulence, was flipped inverted, then fell in totally dead air
with no control action. As he worked on a way to bailout while upside down, the
controls “bit,” and he was able to roll out and fly back to the airport. Fortunately,
he was flying a strong metal sailplane, which no doubt helped. What’s interesting
about that day is, with about ten gliders in a few mile radius of that one pilot’s
dramatic event, we had a kind of data-plot, with the gliders sampling the air under
the storm. It shows how localized, unpredictable, and hazardous thunderstorms
can be. In retrospect, that one pilot may have been in a dry microburst, which
we’ll chat more about later in the chapter.
One criterion, developed by Dan Sowa of Northwest Orient Airlines, is that if
the reported radar top of the thunderstorm pushes up above the tropopause by
10,000 feet, the storm has tornado potential. One can get thunderstorm top reports
from computerized data, the FSS, Flight Watch and NEXRAD. If we have found
our source for tropopause data, we can keep an eye on things, but even without
tropopause data, seemingly excessive tops should have us heeding things
carefully. We should not put precise accuracy into top reports, but knowing the
tropopause height gives us a better indication of how high the thunderstorm tops
will be—the height of the tropopause plus a few thousand where the storm’s
energy pushes severe thunderstorms into the stratosphere. Not all thunderstorm
tops are greater than the height of the tropopause; it’s the only inversion to shut
them off. However, when they do exceed the trop, those storms should get serious
respect!
Hail
Hail is always a problem, but compared with the number of airplanes flying in
and around thunderstorms, not many are hit by hail. As for aircraft actually being
knocked down by hail, some have been pretty well beaten up, but still flew to safe
landing. There is a problem with hail damaging a jet engine, so it loses its
effective power, with some previous incidents resulting in catastrophic forced
landings. Operationally, it’s important to know our aircraft’s procedures for
dealing with hail. Jet engines seem more affected, and usually procedures
recommend turning on the jet engine’s ignition source, then make little if any
power changes. Of any power changes made, we make them slowly.
Most hail comes out of the big overhang cloud that is downwind of a
thunderstorm; if it’s visible, this is the place to stay away from, even if it looks
clear and pleasant there. You might get right under it when the hail dumps, and
again, does so unpredictably. Thunderstorms demand a wide, respectful berth!
Heavy rain can cause engine problems in the form of carburetor icing, and all
precautions must be taken. Sometimes the rain seems so heavy in a thunderstorm
that the engine should simply drown. There is still some question about jet engines
in heavy rain, so it is important to follow recommended procedures meticulously,
which pretty much emulate the hail procedure above.
What hail can do to an airplane. But it flew! (NOAA PHOTO)
On a side note, hail does not do favors to aircraft, whether flying or not. It can
be especially damaging to composite structures, which are different from metal,
especially in repair. If an aircraft has had a hail encounter, either in the air or on
the ground, we should have someone qualified to inspect and repair these
structures, and take a good look at the aircraft, not only for deformation that
affects aerodynamics, but the structure as related to the load-bearing composite
surfaces; composite damage can be less obvious than metal. On composites, even
very subtle dents can mean more than they seem. This came about in the 1960s,
when beautiful fiberglass sailplanes were new concepts, and suffered hail damage
around thunderstorms.
The Bad Part
The big problem with thunderstorms, as we’ve said, is turbulence of sufficient
severity to make airplane control difficult. The turbulence may be severe enough
to tear an airplane apart, but most likely that structural failure follows loss of
control and subsequent high airspeeds that may reduce the airplane’s structural
integrity. Also, flying ham-handedly will not help matters.
Airplanes are pretty tough and, if flown properly, will probably traverse a
thunderstorm safely. This isn’t meant, in any way, to suggest that pilots fly
through thunderstorms on purpose. It is, and always will be, best to stay out of
them. There is some evidence that if certain severe thunderstorms are encountered
at the point of their most potent growth, it may not be possible to maintain control
or keep the airplane in one piece.
Landing with thunderstorms near or on the airport is a hazardous operation.
Most landing shear accidents have occurred with thunderstorms nearby, but some
not so close to the airport as well. Near the ground, as on final approach, is the
most difficult area to handle thunderstorms. There’s no altitude buffer in which to
recover, as we’d have up high, where altitude can safely be lost during a rough
ride. Close to the ground, an uncontrolled altitude loss is disaster.
In the past we’ve always known, through observation and experience, that
winds close to a thunderstorm are squirrely, gusty, unpredictable in direction,
pushy, jerky, violent, and sometimes cover a bigger area than imagined. We
learned it wasn’t smart to get too close, especially in landing, and definitely not to
takeoff into such situations.
Today, research has analyzed and put names on all this: microburst,
macroburst, gust front, downburst, and so on, but this hasn’t changed the action;
it’s all out there, just as vicious as ever. There has been progress in predicting
these conditions, both from ground-based systems as well as on-board aircraft,
but mostly at larger airports through ATC communication or more advanced,
larger aircraft, especially airliners. When we fly our nice general aviation aircraft
into smaller airports, we’re back to the way it was, finding it difficult in locating
these conditions precisely, quickly, and then getting the information to the pilot.
Quickly means a matter of seconds in some cases, so that no matter what system
may come in the future, Doppler radar-based for instance, it’s of no use unless it
gets to the cockpit, and fast! Ideally, the sensing and warning system which finds
wind shear should be located on the airplane, displayed and announced right in
the cockpit, such as we find in predictive wind shear systems on larger aircraft.
This is far more sensible than information from ground-based warning systems,
their warning delayed through intermediary communications from the control
tower at the airport. Of the onboard aircraft systems that provide wind shear
escape data, and are found mostly on larger aircraft, they should not be a panacea
for landing in or near thunderstorms. There are some storms and conditions the
airplane, instruments or not, cannot handle!
The classic wind shear profile is first a headwind, which boosts airspeed and
tends to make the pilot reduce power, followed by a sudden loss of airspeed,
which then requires scrambling to get lots of power back on, plus an increase in
angle of attack—pulling back on the wheel or stick—to combat the severe
sinking. The trick is to pull back to get maximum lift, but not so far as to stall the
airplane. The power of jets makes their “escape” maneuvers dramatic and usually
successful if properly flown. The procedure applies full power—thrust levers to
the stops—as we rotate the aircraft nose up, usually tickling the stall warning;
whether a stick-shaker or otherwise. The target for pitch attitude, on jet transports,
is usually about 15° nose-up. With power-to-weight ratio around 3 to 1, we will
not get this performance from most light aircraft.
The cockpit wind shear avoidance instrument systems help the pilot fly
through the shear with precision, but without this instrumentation, the pilot is just
searching for something in the dark. Another aspect of the instrumentation is that
it defines the event through its sensing of many parameters, then blares an aural
warning, saying, “Wind shear … Wind shear,” to which we react. Without such a
warning, we have to be the parameter computer, and sometimes these events are
not cut and dry, nor easy to define. Either way, we don’t want to get the idea these
instruments find and announce the condition far in advance. When they sound off,
you’re already there!
There’s another important aspect of nasty winds, and that’s the vortex part of a
strong downburst, microburst, macroburst, or whatever you want to call it, which
often is encountered after the classic shear. This vortex area is where the wind
currents are turning and tumbling without any organized pattern or sequence and
can best be described, again, as squirrely. This in turn means the airplane can be
battered up, down, and sideways in a matter of seconds in no comprehensible
order, and there aren’t any instruments for that! The pilot just pushes, pulls, and
twists, trying to handle what’s happening so fast it’s almost impossible to analyze
and fly it. Although fortunate to have only flown such a drastic event in a
simulator, nevertheless, it is a time when we truly feel we’re on the edge of losing
the airplane, requiring efficient and quick response to the attitude indicator; we
realize we’re on the brink of hitting the ground, yet have little, if any, time to
glance at an altimeter or outside. If you ever get the chance to fly these events in a
simulator, it will give any sane person a reason not to get into the predicament in
the first place.
Just before finishing this book revision, I (ROB) had the opportunity to
observe a wind shear event in a simulator, but it was flown on a Boeing 777’s
extremely capable autopilot, which in the real world is not normal procedure. It
was a rare chance to relax and watch these otherwise frantic, hand-flown events.
The footprint for the microburst followed that of an actual microburst /wind shear
accident, years ago and with an older aircraft design. During our simulator event,
the aircraft settled to eight feet above the ground, as read off the radio altimeter,
then recovered. Most interesting was display of angle of attack—finally displayed
on an airliner—that thrashed between -2° to +21° degrees, at a rapid pace that
could not be followed if one used the angle of attack for hand-flown guidance.
However, what allowed the escape, was the computed data of the aircraft’s wind
shear-guidance system, which the autopilot followed precisely, as seen through
the flight director pitch-bar and what we would fly in a real event. The success of
the event was the warning system and the very powerful airplane; anything less
would not have made it, and even this simulated, very powerful airplane came
close to not doing so.
When approaching to land, it also isn’t likely that Mother Nature has politely
set the microburst, shear, or what have you exactly centered on course. So we may
hit the side, corner, or who knows what part of the violent winds. This will, of
course, confuse the action pilots think they are taking.
What all this says is that in some cases we are at the mercy of the tempest.
Obviously it is best to avoid it, and we repeat: do not land or takeoff with a
thunderstorm on or near the airport. This brings up the negative side of
technology. In this case there’s a mistaken idea, conscious or subconscious, that
modern radar can show thunderstorm boundaries well enough so that we can fly
close to them and ATC can also vector us close by the storm. Not true! Distance
required from a thunderstorm hasn’t changed, and detection has not improved
enough to show the sharp demarcation between smooth and turbulent air. In
addition, both pilots and controllers generally have not grasped the fact that a
thunderstorm can develop, become vicious, and do nasty things in minutes.
Consequently, shaving the edge too close is not only basically hazardous, but
there is additional danger in that the air can change from smooth to impossibly
rough in moments!
Even if the airport we are dealing with has a Low-Level Wind Shear Alert
System (LLWAS ) and Terminal Doppler Weather Radar (TDWR ), we should not
drive blindly into compromised, convective weather. There have been times when
an LLWAS didn’t work, because wind sensors are located away from the
localized, 1 mile or so diameter microburst, missing the event. There is also big
improvement with the Doppler radar systems, but we still need to be careful. Also
be skeptical of ATIS weather information; it can be very old, sometimes up to
nearly an hour, compared with the urgency of rapidly changing thunderstorm
activity. ASOS/AWOS is quicker, but again cannot see approaching weather,
although some of the systems detect thunderstorms at the automated observation
site. It is up to the pilot to be cautious and vigilant, using any means to get the
news, regardless of outside help. How? Of course, know the general weather
situation, use our own aircraft’s airborne weather radar, if we’re fortunate enough
to have it, or data link displayed NEXRAD with time-lag caution (more on this
time-lag later in the chapter). Most of all, we should use our eyes to watch
carefully for fast developments and consider proactive deviation to wait things out
before a shear event can happen.
Fast development means big cumulus (cu or Cb) becoming thunderstorms
within minutes. If an airport weather report says “towering cu and Cb,” be careful
to check that they aren’t turning into thunderstorms—especially in the afternoon
or with approaching fronts. This can happen so fast that the airplane landing
ahead of you may fly through an innocuous rain shower on approach, but when
you come in, minutes later, the storm may have developed fully and dumped its
heavy rain and the downbursts, micros, and so forth with it. This has tragically
occurred, just as we tell it here. If there are towering cu and Cb with rain showers
in the area, be extra suspicious and alert for sudden thunderstorm development.
Again, as a reminder, ASOS/AWOS fails here, in that the automatic airport
weather reports do not tell you of towering cu or building Cb. They have to be
supplemented with human observation of the weather for that information, or we
need to use our own eyes.
If we fly an approach—or departure—near thunderstorms and encounter wind
shear or other indicative issues, we should broadcast a PIREP to the tower or
appropriate ATC facility. A timely PIREP can literally be a life saver, even to an
aircraft minutes behind us!
These wind shear and microburst situations are, again, ones in which the pilot
had better remember that ground-based weather data isn’t going to be fully
dependable for getting the information into the cockpit fast enough; it’s up to the
pilot to be on top of it.
Incidentally, the first mention of downbursts, as a result of thunderstorm rain,
was by C. E. Buell in the July 1945 issue of the Journal of Aeronautical
Meteorology .
Their Life Cycle
Thunderstorms, like everything else, are born, live, and die. They do it faster than
one might think, but as one dies, another forms. You do not see all this when
approaching an area of thunderstorms. Large clouds pile up in great masses, and
unless there’s just one lone thunderhead of an air mass or orographic type, there
will be high, intermediate, and low clouds, as well as the cumulus. All these
clouds aren’t wild and rough; most of them are not and contain only light to
moderate turbulence. But buried in those clouds are thunderstorm cells, their
width anywhere from a few thousand feet to miles across. In these cells, things
are rough and wild. They are the heart of a thunderstorm.
The storm may have started as a snappy, jolty little cumulus that formed and
started to grow. It continued to grow and finally became so high that it passed the
freezing level; there it stopped being a simple cumulus and became a
thunderstorm. This is the cumulus stage, and during it, the cloud is almost all
updrafts, some going up 3,000 feet a minute and sometimes more; there isn’t any
anvil or rain.
When I (RNB) was doing weather research, we measured electrical fields and
flew a lot of cu and thunderstorms doing it. One early afternoon, over the Pocono
Mountains of Pennsylvania, I flew into a large, growing cu that was going
through about 14,000 feet but didn’t show any signs of being a thunderstorm. It
turned out to be one of the roughest rides we ever experienced, and the electrical
field strengths were tremendous, which says it doesn’t have to be a full-blown
thunderstorm to be dangerous. The building and early stages are the roughest.
This is not necessarily a rare occurrence. Airplanes have flown through
similar low-topped, but growing cu only to find their ride pretty spicy. One event,
in a wide-body jetliner, had the aircraft pass through an innocent looking cumulus
with tops not much higher than 11,000 feet, but things were thrown around the
cabin and a few folks were injured. The main point here is that if a cumulus is
growing with real clout, it will be rough, most likely well before any precipitation
has developed, which means there is nothing to paint on radar.
The way to study a growing cumulus is by careful scrutiny of the very top part
of the cloud, the shreds and pieces. If one can see a spilling, growing action, and
if it’s “busy,” there’s lots of action inside, and it’s growing. Any indication of a
small, flat, thin cloud around the edges, near the top, is strong indication that this
cumulus is becoming a thunderstorm.
The mature stage follows the cumulus. It begins when rain commences. The
cloud develops downdrafts as well as updrafts, along with heavy rain. It’s still
very rough because of the added conflict of air moving up and down.
After the big anvil has formed off the top, the thunderstorm enters the dying
stage, the wild currents decrease, and it calms down, although it still looks pretty
bad.
That’s the way thunderstorms come and go, but from a cockpit, we want to
know more practical things: Where are the tops, the bases, how far through, what’s
in there, and very important, what kicked them off in the first place? Because if
we know that, we have a start in knowing how to combat the particular storm
we’re facing.
There are three basic ways thunderstorms are created:
1. By heating.
2. By a front.
3. By orographic influences, such as air moving up a mountainside or sloping
terrain.
All of these can unite and produce thunderstorms faster and more violently
than usual.
When a thunderstorm occurs because of air-mass moisture and instability, the
air mass will be heated faster and rise to its condensation level quicker on the
sunny side of a hill, where glider pilots would look for thermals; a flow of wind
up the mountain will also add impetus to the process.
Three stages of a thunderstorm (from left to right):
1. The early or building stage. Lots of updrafts and rough.
2. The mature stage. Heavy rain, possibly hail; up and downdrafts; chopped-up,
rough air; and strong surface gusts ahead of the storm.
3. The drying (dying) stage. Mostly downdrafts. Rain diminishing and not very
rough. But it still looks that way. (NOAA IMAGE)
A front shoving air aloft on its own will do it faster and with more “oomph” if
that front is climbing up sloping terrain, and even more so if it’s doing all this
during the hot part of the day. So hills and mountains make thunderstorms
tougher, as they do other weather, and the rule of extra care in mountains applies
again.
A Clue
When the weather services report actual thunderstorms, they give the direction
from which the storm is moving and its velocity. This velocity should not be
confused with the general speed of the weather system, such as a cold front. The
speed is strictly of the individual storm. There is a definite correlation between
this rate and the storm’s severity. If it’s over 20 knots, the storm will be strong,
and if over 30 knots, it will be severe. In one of our worst airline thunderstorm
accidents, the cells were traveling more than 60 knots. If a rain shower—not a
thunderstorm—is moving over 50 knots, it will have strong turbulence and
deserves caution.
The Different Kinds
Now what do the different thunderstorms mean to us? Air-mass thunderstorms are
generally scattered, and theoretically we see them and wander around, getting
where we are going without flying through any storm.
Isolated thunderstorm. Note overhang extending from the storm. Under the
overhang is not the place to fly! Hail often falls from there, even in the clear air, if
upper winds are strong which blows the hail downwind of the overhang. Also,
close in under an overhang can be quite turbulent. If deviation is started far from
the storm, the miles added to the flight can be insignificant. (PHOTO BY
ROBERT O. BUCK)
Bright spots ahead, but very risky flying through those openings. Both overhang
turbulence and hail potential, as well as lower cu growing and closing up the
hole, potentially trapping us into flying through a thunderstorm. Go around the
area! (PHOTO BY ROBERT O. BUCK)
We see this in the Far West, where thunderstorms occur in classic form. The
visibility in the semiarid areas is excellent, and if anything less than 50 miles is
reported, one looks at it with suspicion.
Here, it is easy to waltz gracefully around the big Cb, watching its dark,
foreboding rain and flicks of lightning from a safe and interesting position.
However, away from these regions of unlimited visibility, air-mass thunderstorms
become more of a problem as we fly in midwestern and eastern summer haze.
If we are working our way through air-mass thunderstorms in reduced
visibility, the place to be is on top of the haze level, where we can see the
thunderheads. It’s worth repeating that when doing this it is important to make
certain that broken to overcast clouds do not creep in under us and that we keep
track of the general weather situation.
Air-mass thunderstorms do occasionally line up in a sort of fake front if the
condition favoring the thunderstorms is strong. This generally occurs in the late
afternoon.
How High?
Thunderstorm tops are high—35,000 to 80,000 feet—depending on the part of the
world. Except in rare situations, any Cb worthy of the name doesn’t stop at
25,000 feet. Almost any fully developed thunderstorm will keep right on climbing
until it pokes up into the stratosphere.
The tops are generally lower in far northern and far southern latitudes, and so
is the stratosphere. We’ve flown over the top of thunderstorms at 33,000 feet
above the North Atlantic, but in southern Italy, I flew next to thunderstorms at
35,000 feet that looked as far above me as I was above the ground.
Thunderstorm tops don’t extend much into the stratosphere, because the
stratosphere is an inversion: the air is warmer than the rising storm’s air, and so
it’s stable and shuts off a thunderstorm, even though momentum may drive it up
into the stratosphere for a few thousand feet or so.
In the United States, the tops are rarely below 35,000 feet. It’s obvious that
small aircraft don’t try to top thunderstorms and big airplanes don’t do so too
often. There are problems for both kinds.
If a pilot does try to top a thunderstorm, or a line of them, that pilot should be
prepared for turbulence, even in the clear; rough air often extends above the
storm’s top. On occasion, we’ve passed over rapidly growing, towering cu—ones
you can just see boiling away as it lunges skyward—but they’re still a few
thousand feet below. They gave us a good solid wallop, as we passed over quickly
in a fast jet, from the rising air currents exceeded cloud development. I’ve heard
slower aircraft doing high-altitude research have felt this lift as a wave-like surge.
In any event, it’s worth avoiding those tops, just as you would any Cb.
A thunderstorm taken at 33,000 feet. There are several things to note: an
overshooting top on the right of storm, possibly sneaking through the tropopause,
meaning a strong storm; and the wispy cloud-like part is possibly hail. In the
lower right, a rain shaft is coming out the storm’s bottom, along with a lower
shelf cloud left of the rain. This storm was moving northeast (right to left) over 30
knots, ahead of a strong cold front. It is not only important to avoid these storms
by considerable distance, it would be foolish to try and top any such weather in
the area. (PHOTO BY CHRISTIAN O. BUCK)
Years back, with sporadic areas of uncontrolled airspace in the United States,
it was not uncommon for folks to soar sailplanes right into the cumulus clouds. In
the early 1960s, an acquaintance did just that in West Texas, entering the cumulus
at around 12,000 feet, with cloud tops estimated in the high teens. The sailplane
was equipped with gyro instruments, oxygen, and the pilot had an excellent
instrument flying background. The climb rate smoothly increased to dramatic
level, later measured off his barograph, in one point of the climb, as 8,000 feet per
minute! He passed through rain, snow, and ice, finally popping out the top near
30,000 feet, out climbing the cloud’s growth. Heading out into the clear, he wove
a dramatic and scenic descent between beautiful cumulus, landing with the last
water drops from melted ice dripping off his wings. This cloud climb was just at
the right time, with not much turbulence, but many such climbs have become
harrowing rides—for those who desire doing such things. Also, sailplanes are
built to stronger limits than most general aviation aircraft, and the folks who did
these things were excellent, old-school instrument pilots.
However, returning to our world of powered aircraft, if an airplane is
staggering along at a high angle of attack, struggling to get on top or stay there, it
may be close to its thrust limit. If an upset or stall occurs from, say, clipping a Cb
top when trying to top one, there’s not enough power to help recovery, and
thousands of feet may be lost in the attempt to get the airplane flying again; if
successful at all. An upset with a jet is a particularly tricky thing from which to
make a recovery. The airplane generally pitches up first, and the natural reaction is
to trim forward; then a dive follows, and big control forces are needed to
overcome the nose-down trim and dive. It’s probably impossible! Very possibly,
the heavy pulling back, plus the speed, will load the stabilizer and “stall” the trim
motor from actuation, and without returning to nose-up trim, there is not enough
elevator authority to allow recovery. There’s nothing to do, except unload it by
letting up on the hard pull and then try to trim. This is one of those theoretical but
highly counterintuitive and maybe impractical tricks. The upset is a complicated
area having to do with speed of sound, shock waves, and air density. The recovery
is often a matter of diving wildly toward the earth, sitting there pretty much
helpless until the speed of sound changes with the temperature increase and the air
becomes more dense, because of lower altitude and higher pressure; then the
airplane gets enough control force for the pilot to recover. A number of these
didoes have occurred, and it’s a testimony to the structural strength of jets that
mostly held together, albeit some were stretched and strained.
A very unique shot of an overshooting top of a thunderstorm, well into the
tropopause. The “flowering” top is probably cloud and hail from extreme
updrafts. We were farther from the storm than it looks—it was serious business—
so with our height about 35,000 feet, this storm was thousands of feet higher.
Because most general aviation flying will be lower and not in view of such a tops
image, it’s more reason to heed and avoid high tops, especially if they’re reported
through the tropopause. (PHOTO BY ROBERT O. BUCK)
Either way, it’s difficult to overstate the danger of trying to top storms, and
even going over them with apparently good speed and control is a more risky
flying condition than one may realize.
The Cloud Layers
If we are flying around storms, trying to stay on top of lower clouds, we can get
into a bad situation. Let us say we are on top of the haze level. We see numerous
cumulus poking up through; they look like bunchy, thick cauliflowers. They are
easy to wander around, but finally they seem to be connected by lower clouds,
and the tops of these lower clouds approach our cruising level. This can happen,
depending on the stage of development, anywhere from 8,000 feet to more than
30,000 feet.
Almost without realizing it, we’ve been climbing to stay on top, and our
airplane is grunting to do the job. We are being suckered in, as the blunt
expression goes.
Big cu tower to either side of our course. Ahead is a lower spot with bunchedup cu. We head for the lower place and hope we’ll get over and beyond before it
builds up to our level.
They Grow Fast
Something we should realize, however, is that those cumulus can build very fast
and turn into thunderstorms. I (RNB) watched one build in Texas. At 11:30 a.m., it
was a pleasant-looking cumulus, and at 11:45 a.m., it was a big, solid, bunchedup-looking cu, and at 12:00 p.m., it towered to tremendous heights, its bottom
was black, rain poured down, and lightning crashed to the ground! (If you
remember the story about the tornado at the glider contest, it was the same day.)
When one stops to consider that thunderstorms in the cumulus stage can have
updrafts of as much as 8,000 feet per minute, with 2,000 to 3,000 feet per minute
fairly routine, it’s obvious that a growing thunderstorm can out climb an airplane
of average performance.
So as we sneak through that “low” spot, we should realize that there’s an
excellent chance that the “low” spot will come up to us, around us, and envelop
us. One cannot try to top growing cumulus unless willing, able, and prepared to
fly through a thunderstorm, because that’s what it may finally come to!
A VFR pilot flying on top of the haze level to spot Cb development hasn’t any
business flying on top of clouds that are bunched-together masses, poking up to
higher altitudes in places, with the ground only occasionally visible. When the
cumulus surrounds us, and the only path ahead is over some other cumulus, or
through low spots between them, then it’s time to turn around or land.
The instrument pilot who feels it’s okay to flirt with growing tops and try to
slide over the “saddles” between them had best remember that no matter how
experienced one is, a stalled airplane in a thunderstorm is in a desperate situation,
and the cleaner the airplane, the more desperate. This isn’t just a jet aircraft issue,
as higher performance, turbocharged single-engine piston aircraft flirt with high
altitude flight.
As we said, if this kind of flying is going to be done, then one must be willing
and able to fly in a thunderstorm. What’s willing and able? First, one must be a
competent instrument pilot who can fly the airplane well in heavy turbulence.
Then, one must have enough instruments, good engine-heat capability, and at least
airborne radar. That pilot must be able to hand-fly while flying in instrument
conditions, as an autopilot cannot always handle very turbulent conditions. Lastly,
this is not the place for a ballistic parachute—parachutes do not do well in
thunderstorms and, as we keep saying, a parachute should not be a crutch for
compromised flying ability or judgment.
Cumulus building. Although we’re looking from over 30,000 feet, if we were down
in the area of, say, 15,000 feet or lower, we’d be facing canyons of growing cu.
These clouds will probably produce thunderstorms, but for now, as they grow, they
probably don’t show on radar, because they’re not wet enough: no rain. So we
would not know they end to the right or see other open areas. For VFR pilots, it’s
a situation requiring calm work to get down and out of it. For IFR, it may mean
an instrument clearance or climbing on top if the airplane can get high enough—
15,000 feet plus—and then wiggling between these towering cumulus. (PHOTO
BY ROBERT O. BUCK)
What’s Inside All Those Clouds?
Let’s go back to our line of towering cu with the lower spot between. As time
goes on, the lower spots will be higher, and finally a solid line of massive cu and
Cb cuts across our course; they may be lined-up, air-mass thunderstorms in the
afternoon, or a genuine front. Either way, it looks impressive and has the
appearance of one big line of thunderstorms.
If we could really see inside that line, we’d find a row of heavy clouds with
numerous thunderstorm cells inside. If we barged through and missed the cells,
we’d get light-to-moderate turbulence and light-to-moderate rain and possibly
hail. If we barged through and encountered a cell, we’d have a wild ride, and if
it’s a cell just growing, young, and vigorous, we’d have a terrible ride.
This has often been demonstrated by two airplanes going through a husky
cold front on the same airway, same altitude, and perhaps only a half hour apart.
One pilot says the ride was horrible, terrifying all the way. The second pilot looks
a little doubtful and may think the first pilot an alarmist, because the second
airplane’s ride had been pretty decent. The difference in rides wasn’t due to a
difference in fortitude between the pilots; it was simply that one missed the cells
and the other didn’t.
What’s Outside All Those Clouds?
It could be smooth, then suddenly a lot of turbulence, some as bad or worse than
in a thunderstorm. It could be the air mass ahead of a front, cold air flowing out
from a nearby storm, and many other possibilities. It often isn’t raining, so we do
not see a radar return. This can be a real issue at night, as with no radar return or
daylight to see what’s outside the windshield, one can be in for a great shock.
One of the worst turbulence events I (ROB) have experienced was at night out
of Albany, New York, in a Twin Otter, when flying for a small regional airline. We
were headed for Saranac Lake in the Adirondack Mountains. There were some
thunderstorms supposedly about 25 miles north of the airport, pretty much on our
course. This was before NEXRAD, computer weather, and our radar was pretty
anemic. Just after takeoff, there was some vague blob of yellow fuzz on the old
black-and-white radar, about 15 miles away. Passing about 4,000 feet, still in the
clear with good visibility, we hit turbulence that was equal to almost any
thunderstorm cell. It hurled and twisted us on every axis. The captain told me to
work the throttles, as he used both hands to fly. In what seemed like forever, but
probably no more than about five minutes, we turned around, descended, and flew
out the bottom of the turbulence, landing back at Albany. The rest of the evening
was cancelled, as thunderstorms came into the area, shutting things down. Never
were we in any clouds or rain; there were always lights of ground contact. When
we shut down at the gate, all we could say was: “Where did that come from?!”
Later, we visited the NWS facility and their only guess was outflow and a gust
front from the oncoming weather, still quite a distance away.
The moral is that we can find very bad turbulence outside a thunderstorm and
that de Havilland builds good airplanes. Where we often learn, in textbook form,
about airflow and turbulence inside, around, and outside thunderstorms, the most
important thing to remember is that things aren’t always by the book, and we
should approach thunderstorm weather as though we are walking on thin ice.
Thunderstorm Detection Systems
This brings us to devices that allow us to look at thunderstorms from our aircraft.
Today, this includes not just airborne—or onboard aircraft—radar, but also
NEXRAD, from the nationwide National Weather Service Doppler Radar sites,
that is transmitted to electronic aircraft displays or portable electronic devices.
There are also devices that read thunderstorm electronic activity—lightning—and
display these areas of lightning on instrumentation in the aircraft; there are various
names for these systems, including spherics, lightning detection systems, and,
because they map lightning on a display, lightning mapping systems. We’ll call it
Lightning Detection.
For years, airborne radar was the only game in town, but many lighter general
aviation aircraft could not fit or afford airborne radar. However, the advent of
NEXRAD and Lightning Detection allows excellent information from which the
masses can now avoid areas of convective weather. This availability reinforces the
statement that we should never flirt with thunderstorms, especially at night and on
instruments, without at least one of these three devices. This is especially true
when we can display NEXRAD on personal electronic devices, whether on the
ground or in an aircraft, giving us a very affordable visual look at what’s out
there.
The best of all possible worlds is combining some or all of these systems in
the aircraft, which is now possible through the many combinations of electronic
displays. However, each of these convective weather–seeking devices has
advantages, disadvantages, and limitations in the information they provide, which
we must understand for best usage, as well as for safety. We must also stress that
the intricacies of each system must be studied and understood before using them
in flight. To do otherwise is unproductive, distracting, and frankly could get us
into more trouble than not. Most of all, we must have the discipline not to be
mesmerized into thinking the information is 100 percent accurate.
We’ll take a very basic look at each system, in lieu of definitive details, as
there’s a book worth of information on each one. However, before doing so, let’s
chat about some basic points of dealing with convective weather, applicable to all
of these systems.
We want to use our radar for a look at the thunderstorms as far in advance as
possible. We then attempt to fly around the entire area, or the biggest area of cell
congestion, rather than getting in close and using airborne radar to squirm
between cells. A good look, with planning in advance, can mean missing the
entire mess. NEXRAD does nice work here, because it looks at weather from
above, along with coverage that can literally be nationwide down to local, so we
have superb strategic-planning ability. Lightning Detection also gives us an
overhead, area-to-avoid scenario.
There are more advantages to reading any radar picture in advance of
reaching an area of thunderstorms. For one, it allows time to tell ATC what kinds
of headings are desired to circumnavigate the weather, well in advance of arriving
in the area, when we very possibly have to compete with everyone else doing the
same thing. (Also, we are saving miles, hence time and fuel, by making that
diversion far away, instead of making a longer mileage jog up close.) In any
event, ATC will be in a much better position to cooperate and give the needed
course changes.
Another point is that once in close to the cells, all will not be easy. New cells
tend to generate close to old cells, so being in an area of cells, and close to them,
means that more will develop, and getting through it all without getting roughed
up, even with tactical use of airborne radar, isn’t going to be easy.
Being in close to the cells doesn’t give much room to avoid them by the
respectable distances that good procedures dictate; we’ll talk about that in a
moment. But all in all, the best way to use either airborne radar, lightning
detection or NEXRAD is to duck the entire area.
Remembering that any kind of radar or lightning detection is a device to help
us miss cells, with airborne radar more capable in close, it’s apparent that when
radar fails to show storms, it’s a useless device. All radar and lightning detection is
fallible; there are times when it doesn’t do the job, and we’ll talk about them here.
Before we do, however, let’s make a point clear: if we are going to enter a
thunderstorm area, depending on radar or lightning detection to lead us through
without getting into a cell, odds are we had better be able and willing to fly
through a cell. However, putting ourselves in this predicament is not a good idea,
especially in a light aircraft; past history shows that over half who do so don’t
come out in one piece.
Radar and lightning detection will take us places we should never go without
it. Suppose we get into this forbidding place and the radar or detection system
fails; now what? Real simply, we are either lucky and fly through without running
into a cell, or we bang into one. If we hit one, let’s hope both we and the airplane
can handle it!
Another area that we need to stay away from, while sneaking around
thunderstorms, is under the higher-altitude “blow-off” clouds on the downwind
side of a thunderstorm. Even though it is clear, and you can see around the storm,
and on to happy storm-free skies, it’s a sucker area, where hail is apt to be, and
often clear-air turbulence as well. In a confused mass of cells and, of course, at
night, we cannot see this area. The blow-off drifts a long way downstream, so a
rule is: avoid a cell’s downwind side, go around on the upwind side, and clear it
by one nautical mile for each knot of wind at the flight level. That may be a lot of
miles, but it’s worth all of them. These wags are well known and heeded by many.
One day, while deviating around a vivid thunderstorm southeast of Kansas
City, Missouri, the upwind side to the weather was south, with not much wind
aloft. We (ROB and son COB) were low, in our Cessna 170, with a few other
light aircraft sharing the same deviation. As we listened to ATC Flight Following,
a turboprop was deviating south as well, pretty much above us at middle altitudes,
and way up high, also above us, a contrail showed a jet changing its course to
avoid their high-altitude needs of storm avoidance. The moment was a great
lesson on how these basic rules of sky and airplane work.
While it is best to go around on the upwind side and avoid the downwind
blow-off area, one should not just skim by the cell on the upwind side, because
there is wind shear in the area caused by a speeding up of the wind close to the
cell. That means turbulence. Give the cell wide berth, and remember the rule of
one mile for each knot of wind at your level. However, there is no definitive
criterion that guarantees what will happen, so again we must be prepared for
surprises.
Airborne Radar
This system, installed onboard an aircraft, sends out a “beam,” which is more like
a skinny cone-shaped signal, that bounces off precipitation—rain—as well as
ground, and returns to our aircraft, being displayed on an electronic screen. The
response time is, for practical matters, instantaneous, so what we see on a radar
screen is not delayed. (This is very important when comparing to NEXRAD,
which has time delay in its signal.) The signal is sent from a round, plate-like
antenna, looking flat-side forward, mounted in the nose of an aircraft or
sometimes in a pod on the wing. The bigger the antenna, the farther and more
accurately we can see weather, which is more of an advantage for big airplanes.
The range of these systems can be adjusted from as little as five miles ahead to
usually no more than 320 miles on bigger systems, with smaller ones usually 100
miles or less. The antenna searches left–right, in a 90° to 180° range.
To deal with a combination of aircraft and cloud height, as well as signals
bouncing off the ground, a pilot can control the up-and-down “tilt” of the left–
right searching antenna. This allows analysis of weather through a broad range of
storm and airplane heights. So, with airborne radar, we have an excellent way of
seeing the cells and avoiding them, although it takes learning, experience, and
radar equipment in good condition. We should never be on instruments when
tactically weaving about nearby thunderstorms, unless we have airborne radar and
know how to use it.
Airborne radar is a tremendous aid in thunderstorm avoidance. What it does is
let us see cells on a screen that we cannot see by eye, because of other clouds and
darkness. How does it do this? The signal is reflecting off the rain inside the cell.
However, radar isn’t a total cure, because it is not showing all turbulence, instead
only that which is associated with rain. There’s lots of turbulence, often the most
severe, outside the rain area! So it’s showing us a “core” of problems surrounded
by turbulence, but the turbulence not shown is something we cannot discern. We
have to “guess” how far away to stay. So, schooling and experience is needed to
get the most from radar; one just doesn’t buy one, turn it on, and go fly
thunderstorms. We strongly recommend that you attend one of the seminars or
radar-schools available, or at least use a home-study curriculum on how to use
radar before going out and trying it. However, a classroom environment with
experienced instructors is very important for picking through the nitty-gritty of
this delicate art; but the best classroom is flying in an airplane with a good radar
system, around real live thunderstorms, with a pilot-mentor who is very
experienced in this fine-art.
The fact that airborne radar bounces off rain also causes a problem, in that it
bounces off the rain of a cell ahead but doesn’t always get through that cell to
reveal one just behind it; the signal is attenuated (weakened). The stronger the
initial cell we are looking at, the more it can attenuate. What does that boil down
to? Example: we are avoiding a cell the radar shows and go around it, only to find
that, when turning the corner, there’s another cell, or cells, facing us. It’s a great
way to get trapped in a blind alley of thunderstorms, the only way out being to fly
through one of them! Modern airborne radars have tried to improve on this, but
systems that offer improvement are still usually for larger aircraft and quite
expensive. Here, if we can augment our airborne radar system with NEXRAD, we
now look down on the weather, which helps us see what is behind the cell that
might be causing attenuation. Also, the use of a Lightning Detection can do the
same thing, but only if there is lightning being registered from the farther storm.
Radar’s important feature is that it reflects from rain, but at high altitudes, the
cloud doesn’t have rain. It has snow and ice crystals instead, and sometimes hail.
We can find, on occasion, “wet hail”—hail not totally frozen in that it has a
coating of water outside its frozen core—which along with any rain thrust high in
strong lift, will give some reflection. However, up high we’re usually in frozen
precipitation, and the radar beam doesn’t reflect as well from this frozen stuff, and
the cell becomes difficult to see on the screen. The way to try and overcome this
is to point the antenna down toward the rain area for a picture. The trouble is that
airborne radar then bounces off the ground too, the picture becomes confused, and
individual storms are more difficult to see, in that they show as blobs amidst
ground “clutter” on the screen, with a dark area behind known as a “shadow.” It
takes a lot of experience to read a scope under these conditions, and even with
experience, it doesn’t always work. To help the ground clutter issue, if we know
the terrain and rough distances from it as we are flying along, we can anticipate
mountains, valleys, cities, and bodies of water that allow us to anticipate what is
ground clutter and what is not. New radars are just coming into play that use GPS
information to know where we are, and along with vastly improved computerized
and automatic antenna tilting, figure in terrain and help alleviate attenuation
problems. It’s new, but an excellent improvement.
Airborne radar maintenance problems are not always just a simple matter of
whether the radar works or not. There are degrees of radar maintenance, and this
makes thunderstorm reading difficult and less clear. The radome itself, its special
paints and coatings and structural condition, also play into this equation.
It is necessary to get all the information possible from the manufacturer and
learn to recognize when radar equipment is not putting out its best performance.
There are various ways of doing this; one is to note how much “gain” (signal
strength) the system requires for a picture. However, this is best learned for each
system we operate. If we do turn down gain, which for example can be used to
verify a storm’s intensity, we must remember to return it to normal position, as
forgetting about it can hide weather we may need to see, consequently running us
into a cell that the radar couldn’t detect at the lower signal strength.
Let’s list some airborne radar limitations:
1.
2.
3.
4.
5.
6.
7.
8.
Failure.
Equipment deterioration.
Attenuation.
Poor reflection from frozen particles.
Difficulty reading in mountainous terrain.
Pilot experience with radar.
Radar only shows rain areas.
Ice or damage on a radome causes false or poorly defined targets.
An important point is the general guide that most professional flying
operations use in determining how to miss cells. It’s based on temperature and
altitude. They say to miss cells, when using airborne radar, by the following
distances:
• When the temperature is above freezing—5 miles
• Temperature below freezing—10 miles
• At altitudes above 25,000 feet—20 miles
Also, the above are minimums, and it’s better to give the cells a wider berth if
possible; 20 miles minimum, at all times, which can also be considered for
NEXRAD and lightning detection systems. If a thunderstorm is approaching the
severe category—which the weather service defines as 50 knots of surface wind
and ¾-inch hail—we should consider a 50-mile deviation.
Again, remember that radar only shows rain areas, and even the new radars
that boast turbulence detection by use of Doppler techniques are only telling you
whether a rain area is turbulent or not and how much. It isn’t revealing anything
about the turbulence outside the rain area, where some very tough stuff can lurk.
NEXRAD
NEXRAD, the acronym for the National Weather Service’s NEXt Generation
RADar, is convective weather information homogenized from, as of this writing,
155 WSR-88D Doppler radars at NWS facilities across the United States. These
radars read precipitation rate, measured in decibels (dBZ or dB) between zero to
75, and are presented as 16 levels of dBZ, as well as in color.
NEXRAD data also shows velocity and direction of convective weather, and
sometimes storm height, and that, along with the dBZ color criterion mentioned
above, is what we mostly use in aviation. As previously mentioned, we remember
the orientation of NEXRAD is as if we are looking down on a weather map, rather
than horizontally ahead, as in airborne radar.
We again recall that precipitation rate is not a definitive measurement of storm
intensity, with a severe thunderstorm requiring at least that 50 knots of wind and
¾-inch of hail or a tornado. However, a lot can happen that will make flying
miserable or maybe impossible, including microbursts, without a thunderstorm
being rated as severe.
NEXRAD has a lot of other modes we don’t use in aviation, but that weather
services use to analyze the sky. It is the system for ground-based thunderstorm
evaluation, whether for aviation or the many other concerns the weather service
uses radar to detect. Also, where we think of radar showing thunderstorm
information, NEXRAD picks up rain in all sky-conditions, so it could be
precipitation out of a far more mundane weather situation. Hence, another reason
we have to understand weather systems, so we know what NEXRAD is looking
at. With recent upgrades to what is called dual polarization, it allows better
detection of freezing levels (which could help us in aviation with respect to icing),
wind analysis, severe weather issues, and more. A mode we can see on the NWS
website is Relative Velocity, which leaves out a storm’s movement over the
ground, instead exhibiting the storm’s internal directions, which is helpful when
looking for tornados, among other things. NEXRAD can even see swarms of
birds, bats, insects, and sometimes windmill farms giving false vorticity/tornado
indications from the complex airflow around them. As we fiddle with NEXRAD
in aviation, it’s worth remembering that weather service folks take months of
training to learn these systems; something to ponder should we get heady in
thinking we are experts in using NEXRAD.
The process of creating the mosaics of NEXRAD entails collecting each
individual radar’s return, sending it to and through computerized processing, then
transmitting it through services to our viewing preference: television, computers,
personal electronic devices, or an aircraft’s instrument display. This processing of
radar data takes time, sometimes nearing 10 minutes or more, from when local
radar sites begin to process what we are looking at in an airplane. This time delay
is very important to remember, especially in comparison with airborne radar’s
instantaneous presentation of convective weather.
The obvious big gain to aviation from NEXRAD is not only do we get an
efficient radar display for preflight planning and trend analysis, we also can use it
in the air, which pre-NEXRAD was only the lofty world of those privy to airborne
radar. But as we said, there are limitations and knowledge we need to fully know
and understand before smugly heading off into a sky full of weather.
The delay issue of NEXRAD information is probably the most important
restricting feature of the product. This is why NEXRAD is best used in strategic
avoidance of weather—avoiding the whole area in lieu of closely sneaking around
cells, which, if you have to and as mentioned before, is better done with airborne
radar’s instantaneous information. The reason is simple: the delayed presentation
can have a thunderstorm farther downwind than the radar shows, and if at night or
in cloud, you can run into it. For example, if a cell is moving at 30 knots and we
assume a 10 or more minute delay of the NEXRAD data, the cell is a minimum of
five nautical miles farther along. If we are closely deviating around this weather,
on the downwind side for some unfortunate reason, we may run smack into the
cell. So, when using NEXRAD around convective weather, the time delay makes
it even more important to deviate on the upwind side. However, in an area of
thunderstorms, even upwind, we can have another storm right behind the upwind
side of the one we are avoiding.
Most dedicated NEXRAD displays show time-delay information, but it is not
—at least as of now—the total delay amount. It shows only the delay between
transmitted data and not for the whole process if creating the NEXRAD mosaic.
So, for example, looking at two minutes on a screen may actually be that 10
minutes or more we mentioned above. This example is taken from a fatal
accident, where the pilot was downwind of convective weather moving at 45
knots and ran into a thunderstorm cell, where the aircraft came apart. In that
accident’s case, a turn away would have cleared the whole thin line of the area,
where the pilot could have either found broad space to pass by the weather or to
land somewhere safe until the weather passed. This is not the only incident, and
enough have occurred for the National Transportation Safety Board (NTSB) to
issue a Safety Alert in 2012, warning about the NEXRAD time delay, although
many had realized and warned of this before the NTSB Safety Alert.
Another aspect of NEXRAD is the type of radar search data that is presented.
The search that sees precipitation, hence convective weather, is “Base” and
“Composite” reflectivity. Reflectivity refers to the radar mode that reflects off
rain.
Base reflectivity means the radar searches at a low angle with the beam center
at a half of a degree above the horizon. It’s a more concise signal, doing a very
good job of reading a storm’s intensity and movement. Some base reflectivity
mosaics might underestimate a storm’s intensity. If interrogating a rain-bearing
cumulus or thunderstorm thousands of feet high, this dedicated beam slices
through only part of it, and depending at what height the heaviest rain is located,
may miss this precipitation altogether. Or, it could go under or over the storm
altogether, depending how far away the storm is located from the ground-based
radar facility.
Composite reflectivity interrogates by taking multiple beam scans of the sky,
between half a degree up to 19½°, allowing a look at a storm in a vertical column.
It’s a more three-dimensional view of reflectivity, giving a more complete view of
a storm’s precipitation. Composite reflectivity can overestimate a storm, but this
more complete look at the storms development, hence structure, can indicate
storm severity that otherwise would not show in a base reflectivity image.
Consequently, one needs to take the conservative view and consider any
NEXRAD indication of precipitation, in a potential thunderstorm area, as the real
deal and a place to avoid.
An important area where base or composite scans can make a difference is in
mountainous terrain, and particularly in high mountains. Terrain will stop any
radar signal dead in its tracks, hiding precipitation returns that could be very
important for us to see. This effect is more susceptible to base reflectivity, because
it’s a low beam, but can happen with composite if faced with really tall terrain and
weather a fair distance behind it. A great example is looking at the Burlington,
Vermont, NWS NEXRAD site on a day there is precipitation to the east, where
about 20 miles away the Green Mountains stretch north and south. Base
reflectivity will show little or no precipitation east of the 3,500-to 4,000-foot
mountains. That is a real setup as we happily head off over the mountains, only to
bash into weather that had its rain hidden from the blocked radar signal.
To get the best idea of what a storm area is up to, we should compare base and
composite reflectivity. This gives us a more thorough look at the weather. One
important variation is the more sensitive read of precipitation in composite scan
which could mean serious issues developing such as high-level hail or a potential
microburst that, before long, may be pouring out of the storm. Overall, it could
expose a thunderstorm issue far more intense than previously thought, but then
again, we should consider all thunderstorms as something to avoid.
At this point, it’s important to confuse the issue and point out that having a
choice of seeing base or composite reflectivity is usually a function of looking at
radar data from weather sources such as the NWS ADDS site. You can switch
between base, composite, static, or looping mode. However, when we receive
radar information through a weather source, be it data link to our aircraft, a
personal electronic device, or TV, we are usually offered only one reflectivity:
base or composite. It is important we understand what we are looking at and make
the necessary compensation for how the NEXRAD mosaic is presented.
Base Reflectivity NEXRAD image, with its low half-degree beam, from
Burlington, Vermont. Note the weather’s farthest eastern reach stops about
Middlebury in central Vermont, up against the Green Mountains, the highest of
which is about 4,000 feet. (Refer to composite reflectivity image below.)
On some of the more dedicated aircraft presentations of NEXRAD, other bits
of data will be available, such as storm direction, intensity, possible tornado
activity, lightning, and echo (cloud) tops among others. This data comes from
other analysis of NEXRAD by the NWS and other sources. It is then packaged
with the data-linked weather for our aircraft. These highlighting enhancements
should provide further impetus for us to avoid the whole area and not weave
through it. Also, in referring the dBZ ratings of precipitation rate, anything over
40 dBZ is considered something we really need to avoid, and if we see colors
relating to over 60 dBZ, that is when we are looking at potential hail or
microburst. In reality, few if any aircraft NEXRAD systems, let alone the majority
of pilots’ amateur use of this equipment, either airborne or ground-based, will
allow us to analyze if there is hail, microbursts, certain turbulence levels or
whatever. And if we see dBZ ratings of any level, knowing it’s an area of
thunderstorm potential, in lieu of an area producing non-convective rain, we need
to avoid the area. Again, if a Cb is developing, but not yet raining or raining of
light intensity, it can still give us a wild ride. Radar is not the whole story!
Composite Reflectivity from Burlington, Vermont, with its higher radar scans, at
the same time as the base reflectivity image above. Now we find out there is
activity over and beyond the mountains to the east. Taking off at night or in cloud
IFR, heading east, thinking no weather was beyond the mountains, we could be in
for a real surprise!
Lastly, when NEXRAD system data is presented to us, its smallest resolution
is a little two-kilometer square on the mosaic presentation. So if we have a radar
display that can hone in real close, we’ll see little two-kilometer squares and
nothing tighter. A lot can happen in that little square, including things like a
microburst that can knock us flat out of the sky.
Let’s list some NEXRAD limitations:
1. Time delay in NEXRAD mosaic presentation causing false assumption of the
weather’s position.
2. Terrain blockage of signal can miss or underestimate important storm data.
3. Should know the type of reflective signal, base or composite, and respective
limits.
4. Mosaic accuracy is no smaller than a two-kilometer square.
5. Lost signal possibilities.
6. Pilot experience with NEXRAD
7. Only shows storm precipitation.
Lightning Detection Systems
Before radar, we avoided thunderstorms by experience, witchcraft, and tricks. We
didn’t avoid all of them, because we couldn’t “see” the cells, so we unknowingly
flew through them, from time to time experiencing very rough rides, and we lost
airplanes, too.
Coming up on a line of thunderstorms, we’d watch the lightning closely and
try to avoid going into the mass of clouds where the lightning was “hot.” It didn’t
always work, because the lightning frequently seemed to cover the sky due to
reflection within clouds and the general bombardment.
We also tried to tune our ADFs to a low frequency, away from any station, and
then watch the needle, thinking it was pointing out thunderstorms and where not
to go. Some claimed considerable success with this technique. My own success
was of very low order, and I (RNB) never thought much of the idea.
We looked up to the tops, picked the lowest, and went through under that. For
a time there was a theory that flying through the heaviest rain was the smoothest
way, but that didn’t work either. One thing we all agreed on was not to land or
take off with a thunderstorm near or on the airport. Decades later, research found
these basic “gut-thinking” rules had validity. It was revealed the intensity of
updrafts and electrical power increase exponentially with storm height. We have
also learned that landing and taking off in thunderstorms is not only unwise due to
violent turbulence, including excessive vertical air currents, but also due to wind,
heavy rain, and disastrous microbursts.
A few decades back, Paul Ryan of Ohio was flying his Cessna Skylane across
one of the Carolinas when he tangled with a thunderstorm that almost did him in.
The turbulence was wild, and he felt lucky to get through it alive. Mr. Ryan, an
electrical engineer, decided that something needed to be done about thunderstorms
and avoidance for the single-engine “little guys” of aviation, because most
couldn’t afford radar, and even if they could, installing a radome on a small singleengine aircraft was a unique challenge.
He started, much as we did, with ADFs and eyes, to “see” the electrical
discharges—lightning—that go with all thunderstorms. After much research and
development, he created what’s now known as Stormscope. This device reads the
electrical discharges (lightning) and displays them either on a dedicated distance
and direction display or on electronic instrumentation of aircraft so equipped. The
ideal situation is when we can compare this lightning data with other weather and
navigation information. Unlike airborne radar, there are no movable antennas or
radome, rather, just a small, fixed antenna and the instrument panel display
showing “+,” “x,” little lightning bolts or dots and colors—depending on the
system and intensity—that are electrical discharges, hence thunderstorms. Also,
the lightning data can often be displayed through a 360° range, so one can “see”
the storms all around before takeoff, which can be very handy.
Along with Stormscope, here came a competitor called Strike Finder, and
now, years later, we have further iterations of this technology through various
avionic manufacturers. The technology detects and displays lightning, indicating
convective weather to be avoided. This science is really a lightning detection
system that maps the lightning on a display, and another term for the often used
spherics or sferics— a word derived from radio atmospherics. Most accurately, it
is a lightning mapping system, but that term is also used for systems that display
lightning derived from a long-range, ground-based detection network, which we’ll
talk about after this section. So, in some hope of commonality, we’ll refer to this
type of unit, formally known as sferics, as a Lightning Detection System (LDS ).
An actual in-flight, split-screen MFD display of lightning detection (left) and
NEXRAD (right) for the same time and place: heading north–northwest on 200mile scale at 8,018 feet. Dots at the top of the right split screen are airports. On
the left split screen are “X’s” indicating lightning/thunderstorm activity, but
NEXRAD shows nothing in the same area, except a 20,000-foot precipitation
return. Fifteen minutes after this picture was taken (second image unavailable),
more precipitation appeared in the “X” area. These time differences are
indicative of NEXRAD delay issues. The large precipitation area in the NEXRAD
image’s lower right shows no lightning, for whatever reason, but with 30,000-foot
tops, moving over 30 knots, it is a place to avoid. Overall, we see the benefit of
having both lightning detection and NEXRAD—the only thing better would be
adding airborne weather radar. Most important is realizing all the variables make
weather “strategic” deviation—avoiding the whole mess—the prudent choice.
(PHOTO COURTESY OF L-3 AVIONICS SYSTEMS)
In basic explanation of how lightning detection works, we are going to refer
between two basic types of lightning: Cloud-to-Ground (CG ), its nature being
obvious by name, and Intracloud (IC ), again pretty obvious as to where it lives.
These two types of lightning tell us different stories. Research has shown that
intracloud lightning begins early in a storm’s development, often as much as 10 to
30 minutes before cloud-to-ground lightning. Also, intracloud lightning can be
active as much as 10 minutes or so after the cloud-to-ground lightning stops.
Intracloud lightning generally occurs more frequently than cloud-to-ground,
sometimes upward of ten times. So in theory, intracloud lightning is well in place
during the earlier and more intense, updraft development phase of a thunderstorm,
often before significant rain begins. And we remember rain is required to show
weather on radar.
Now when a lightning detection system shows lightning, we must consider it
as a real thunderstorm, and should avoid the area. There is debate, however, as to
how early in a storm’s development we are seeing it. This is because lightning
detection systems are seeing, as a majority, only the later cloud-to-ground
lightning, as they supposedly only work at the very low frequencies of cloud-toground lightning’s radiation. Intracloud lightning is of higher frequency radiation,
which can sometimes be picked up randomly if we are really close to an area of
lightning. What this all means is that if we are not receiving indication of the
earlier intracloud lightning, then we are also not seeing a thunderstorm in its early,
developmental stage, which can be that most turbulent time. Hence, like any
thunderstorm detection system—radar or lightning—we do not have total
guarantee of avoiding all related turbulence and everything that goes with it.
However, no matter the issues mentioned above, lightning detection is a very
sensitive indicator of storm activity, so a real key is lightning rate; if there’s a high
lightning rate, the storm has serious clout, and we should absolutely stay away .
In reality, any lightning means a thunderstorm, and we should avoid it no matter
the intensity.
Lightning detection systems also offer accurate azimuth (direction), but can
vary in distance accuracy. This latter issue is called “radial spread.” It’s caused by
what we see as one lightning strike really having multiple strokes of lightning
during that supposed single strike. The strokes can vary in intensity, so a weak
stroke seems far away and a strong one close by. Also, a lightning signal’s
“bounce” can be affected by bouncing off the ionosphere, kind of like an AM
radio station, where you hear a station 1,000 miles away at night, but not in the
day. As lightning detection systems must make assumptions of cell strength from
the data received, there can be variations in distance accuracy, but supposedly,
newer systems have modes where algorithmic software improves this issue of
radial spread.
A lightning detection system aircraft installation can, on occasion, show
lightning display that isn’t from lightning, but instead things like an airport’s
underground electrical lines, say for runway lights, or strobe lights in the air. This
is of minimal concern versus the benefit of lightning detection, but a quandary if
looking at lightning data on our detection screen, before we takeoff in
suspiciously clear air.
Manufacturers of these systems are claiming dramatic improvements of
detection capability, and these systems often see lightning a fair time before radar,
hence rain, which is also usually when cloud-to-ground lightning is prevalent, so
one wonders what’s really being detected as to CG and/or IC lightning.
If there is eventually an airborne system that accurately reads both intracloud
and cloud-to-ground lighting—referred to as total lightning—we’d have a pretty
exciting system. There are ground-based versions of this today, but they are only
used in specific situations or are not adequately promoted for their potential
benefit. However, even if a ground system became available to aviation, we’re
probably back into a NEXRAD-style “ground to eventually airplane”
transmission delay issue, which, with total lightning’s benefit of showing rapid
storm change, kind of reduces the benefit of the whole idea.
With an aircraft installed system, which has appropriate calibrations and
indications, we’d possibly have, for the first time, a system to sense the excessive
turbulence in developing thunderstorms, before rain is visible either by eye or
radar; a potentially helpful new addition to tactical weather avoidance There are
also indications that total lightning may give accurate prediction of microburst
and tornado activity. A last point is that as intracloud lightning trails on a bit after
the CG lightning ends, so we’d potentially avoid a late in the event surprise of
unwanted turbulence. But again, as no lightning detection system has definitively
shown data that proves their system can always detect both intracloud and cloudto-ground lightning, we must assume these are not full total lightning systems.
The obvious big benefit of lightning detection systems is that without any
form of radar on our aircraft, either airborne or NEXRAD, lightning detection is
our ace in the hole. If our aircraft has a combination of airborne weather radar and
lightning detection, but no NEXRAD, the lightning detection system will have
considerably more range than all but the best airborne radars being flown at high
jet altitudes. The obvious benefit here is excellent advance warning of weather
and subsequent long-range planning of deviation. Also, as said before, with this
convective weather detection combination, lightning detection lets us see around
airborne weather radar’s attenuation; we recall that attenuation is where a cell
painted on airborne radar blocks detection of further weather behind that cell. If
we have confusion on airborne radar between weather and ground return,
lightning detection can help us decipher what’s weather and what isn’t, which is
especially helpful in mountainous terrain.
Going back to NEXRAD, there are places where the NEXRAD system does
not offer coverage, be it beam blockage from terrain, the NEXRAD mosaic being
out of range of radar facilities, or distant parts of the world where no such system
exists. The NEXRAD data may suddenly end, deceivingly allowing us to think
any convective weather did the same. However, because lightning detection is
aircraft-specific, it will still show convective weather out of NEXRAD’s reach,
which could really save our bacon. Of course, airborne weather radar will do the
same, but that is the only commonality between airborne weather radar and
lightning detection: they are working from the aircraft and are not ground system–
dependent.
Now if we have lightning detection, airborne weather radar, and NEXRAD
onboard, we can work these systems as complements to each other for excellent
convective weather avoidance. Because radar reveals the rain area and, one
thinks, turbulence, radar leads us around the rain, hence supposedly the
turbulence. Lightning detection shows the lightning, which says the rain is a real
thunderstorm and we should stay out. If we see lightning detection data outside a
rain area seen on radar again, that’s a place to avoid. In theory, if there is rain but
no lightning return, it isn’t a thunderstorm, saying there’s little or no turbulence in
that rain, awful though it may look. Numerous tales are told of pilots seeing dark,
foreboding rain, but Stormscope or Strike Finder not showing lightning. Brave
souls have flown through these areas and had good rides. Similar stories are told
of paralleling a front that looked mean, nasty, and impenetrable, but these systems
showed an area without electrical discharge and a way though. However, like so
much of aviation weather, this is not a 100 percent perfect solution, so all such
events should be approached with caution, experience, and common sense.
Putting all this together, it seems that if a lightning detection system is showing us
lightning, the storm is the real deal, and we should avoid it accordingly, which is
the most conservative—and sensible—choice.
So where does it come out? Lightning detection no doubt shows the location
of thunderstorms and can help us avoid the storms, but not closely enough to
weave through a mass or line of them, unless a clear, wide path is revealed.
Ideally one would like to have lightning detection, airborne radar, and NEXRAD
merged together on one display. Some people have remarked that they use
lightning detection more than airborne radar. Lightning Detection Systems are
there for all aircraft, but are an especially helpful option for single-engine and less
expensive aircraft. This is lightning detection’s role.
We can be thankful that Paul Ryan took the initiative after his thunderstorm
encounter and did something about it. As with all convective weather detection
devices, be it radar or lightning detection systems, there are pros and cons that can
get us in trouble no matter the system. In using these systems, we need to
understand how they work, how to use them, and the quirks each will have in
their individual installations. As said earlier, and certainly worth repeating, any of
these devices should ultimately be used to avoid the areas of convective weather,
when at all possible, and lightning detection systems are a very worthy player in
convective weather avoidance.
Let’s list some Lightning Detection System limitations:
1. Use in weather area avoidance, not for close-in tactical weaving.
2. Systems only show lightning data, not precipitation.
3. The systems only show mostly cloud-to-ground lighting, which occurs later in
a storm’s development than intracloud lightning, hence still not consistently
revealing early and turbulent storm development.
4. Pilot must be familiar with each aircraft-specific lightning detection system
installation, both with the system in general and effects due to aircraft
installation.
Data-Linked Lightning Mapping Information
We need to understand that Lightning Detection Systems should not be confused
with lightning information that is data-linked or vendor-supplied for display on an
aircraft multi-function display, GPS unit or portable electronic device. As said
earlier, this data comes from other lightning detection sources, including the
National Lightning Detection Network, and is cloud-to-ground lightning data.
This is the lightning information most colloquially related to the term “lightning
mapping.”
This data is displayed like NEXRAD, so we are looking at it from above as we
fly along, unlike lightning detection systems or airborne weather radar, which is
from the aircraft. Lightning mapping, as shown on aircraft data link, is also
subject to NEXRAD-style time delays, but the delays are not as long due to
quicker processing of multiple data feeds.
Since lightning mapping information is cloud-to-ground lightning, like the
lightning detection system onboard our aircraft, we approach it with the same
understandings of what cloud-to-ground lightning tells us of a storm. Like our
aircraft-installed lightning detection device, there is a worthy use for this
information, and usually when we’re using lightning mapping, we have other
information displayed, such as NEXRAD, satellite data, and so on. Another
benefit is this lightning data covers a broader area than NEXRAD, again giving us
an indication of convection should NEXRAD be out of range or unavailable.
What we often see displayed through data-linked lightning mapping and vendor
lightning data are little lightning bolts on our display, and wherever they are
present, even if isolated from radar data, we should fly clear of the area.
A Summary of Convective Weather Detection
1. Even with airborne radar, NEXRAD, and/or lightning detection systems, don’t
fly into cloud areas containing embedded thunderstorms, especially if you can
avoid them in the first place.
2. If in cloud or darkness, and avoiding thunderstorms with any avoidance
system, give them as wide a berth as possible. Don’t just skim around the edge
of cells; use at least the minimum mileage rules.
3. It’s best not to think light precipitation in the vicinity of known thunderstorms
is not too bad. If the storm is growing, it can change very fast. They are all
thunderstorms; some are just worse than others, but we can never be sure
how bad … until we are in them.
4. Know your geography; terrain knowledge allows an understanding of what
airborne radar may see as ground clutter and what NEXRAD does not see
due to beam blockage caused by terrain.
5. Take courses and/or seminars on each thunderstorm detection device we use,
then practice and stay current.
6. Look out the windshield; learn to visually evaluate convective weather,
especially as it develops to thunderstorms, not only the storm’s character and
state of life, but the direction it is moving. As those old-timers would say,
thinking of that airborne radar antenna sweeping back and forth: “One look
is worth 1000 sweeps.”
ATC and Thunderstorms
Thunderstorm intensity is graded for ATC purposes. The four terms “light,”
“moderate,” “heavy,” and “extreme” are used when ATC tells us what they see on
their weather information. Air Route Traffic Control Center (ARTCC ), which is
enroute or center ATC, only gives moderate through extreme, not light
precipitation. Terminal Route Approach Control (TRACON ) facilities, which are
local airport (approach and departure) control facilities, give all four. These four
terms are honed down from the 16 dBZ levels of precipitation intensity ,
previously discussed as NEXRAD’s measurement and display of weather. ATC’s
weather data is collected from NEXRAD and is also subject to the processing
delay and other issues. But overall, there is improved convective weather
presentation on ATC radar, and controllers are better equipped to help pilots. As a
majority, ATC controllers seem very concerned about and accommodating of our
weather needs.
The four levels of precipitation, in relation to dBZ, are as follows:
Weather radar echo intensity
dBZ level
Light
Moderate
Heavy
Extreme
< 30 dBZ
30–40 dBZ
> 40–50 dBZ
50+ dBZ
There are still some potentially misleading aspects of the system that need be
understood and taken into consideration.
For example, what ATC may call light precipitation can be in a cumulus that’s
just about to become a full-blown thunderstorm, rapidly increasing to heavy or
extreme when it suddenly dumps its water. Remember, the rain area of a
thunderstorm is not the only place severe turbulence can be found.
A situation that can be misleading is being told something like: “an aircraft
ahead of you went through that area of light precipitation and had a good ride.” If
things were quickly moving and growing, we could have a real surprise. What
would improve this system of ATC weather information would be a trend of the
weather’s status; for example, light precipitation with increasing areas of
moderate precipitation, and so forth. This is tough to do from ATC weather
information and would have to come as supplemental information. There are inhouse NWS meteorologists at ATC facilities who can be consulted, but again, the
time for discussing and introducing this information to aircraft is limited to traffic
level. Ultimately, we as pilots need to have a feel for the weather we are dealing
with, such as if it is isolated, air-mass thunderstorms or a more serious
frontal/squall-line situation. This, of course, is necessary not only in our preflight
briefings, but by following weather en route.
With respect to the ATC system, a controller’s primary job is air traffic
separation, in an ever busier sky. They are not required—and sometimes do not
have the time—to volunteer weather information. If we, as pilots, need this
assistance, we should let ATC know. Remember, they do not know our experience
level or needs unless we tell them. In the case of thunderstorms, it might be
vectors out of weather, an altitude change, and so on. If ATC can’t comply
without our declaring an emergency, then we may have to do so; it’s better than
putting ourselves up against a wall. However, we should strive to make sensible
and well-planned flight decisions ahead of time and not use a declaration of
emergency as a crutch.
Unless a pilot understands the workings of thunderstorms and radar and ATC’s
limitations, this dissemination of thunderstorm intensity levels can be misleading,
creating further hazards, rather than avoiding them. The information should be
used with caution and respect.
More about Air-Mass Thunderstorms
We were talking about air-mass thunderstorms; it’s important to realize that these
come in several different kinds. The simplest is the convective kind. They are an
eventual development from a thermal source, a hot spot on the earth. Obviously,
when the sun goes down, the heating does too, and the storm dissipates. If it
doesn’t, then the storm isn’t just a convective storm; something else is creating it.
The real thermal convective storm may take a while to die and doesn’t disappear
as soon as the sun goes down; a big bunch of clouds hangs on into the darkness
with an occasional flicker of lightning, but it’s on its way out, and one can see and
feel that it isn’t holding or increasing in strength.
Thermal convective storms are easy to run around when they are scattered or
isolated. Sometimes, however, they aren’t so scattered. Whether they are scattered
or broken depends on how much moisture is in the air mass and how unstable it is.
This is pretty difficult for a pilot to judge, except that forecasts give an idea
simply by the number of storms they predict. Our old friend the temperature–
dewpoint spread is another indicator; if the dewpoint is high, the air is moist and
more likely to produce storms. You can “feel” this too, and because weather
appraisal is inexact to begin with, one shouldn’t laugh off old sayings like those
about rheumatism that hurts when it’s going to rain. On a hot, muggy summer day,
any weather-conscious person can sniff the likelihood of storms.
We are still basically animals, and despite years of sophisticated city living
and separation from the primitive state, we have a feel for weather, feeling it in
our bones, as the saying goes. Naturally, we don’t use instinct for our basic
weather judgment. Science is the important thing, but that old instinct is worth
using, particularly when it raises suspicions that all is not as good as a forecast
may say it will be.
A Cloud Base Hint
Incidentally, temperature–dewpoint can help in finding the base of cumulus
clouds, or how high one will have to climb to get up out of the lower-level
convection. Take the temperature–dewpoint difference in degrees Celsius and
multiply it by 400. The answer is the altitude above the ground, in thousands of
feet. For example: temperature = 35 degrees, dewpoint = 20 degrees. The
difference is 15 degrees. This times 400 is 6,000. The base of the cumulus will be
about 6,000 feet. (If dealing with degrees Fahrenheit, obtain temperature–
dewpoint difference times 2, plus about 400 feet for the bases. For example:
temperature = 93 degrees, dewpoint = 67 degrees, difference = 26 degrees; 26 × 2
(add two zeros) = 52(00) + 400 feet makes the bases about 5,600 feet.) That’s one
reason, during the day, cloud bases are lower over valleys and higher over hills
and mountains.
Other Air-Mass Thunderstorms
To sum up, air-mass thunderstorms are generally isolated and occur in the
afternoon, when heating has had a chance to work on them. They can also occur
in overrunning air, not necessarily from a warm front, but from slopes acting like
a warm front. This will carry thunderstorms into the night, but probably their
bases will be high.
Air-mass thunderstorms can bunch up and look like a front, but we can
generally fly around them. In the parts of the world where visibility is good, such
as in the far western United States, this is easy. In the more moist sections, where
haze reduces visibility, it’s more difficult; a pilot is best on top of the haze level,
where the cumulus buildups can be seen. It’s important, of course, not to get
trapped on top when doing this. It is also important not to try to top
thunderstorms.
As said before, it’s dangerous to sneak around underneath high, overhanging
anvil clouds, because that’s where hail falls from. It falls more outside the storm
than inside it.
It is dangerous to sneak under thunderstorms where visibility is reduced and
there’s a chance of flying abruptly into clouds, rain, and turbulence. Mountains
may be buried in the haze, too, as are communications and other types of towers.
Also, if a pilot runs into turbulence down very low, the situation is more
hazardous than flying a bit higher, where there is room to wrestle the rough air.
While trying to get past a line of thunderstorms when flying down low, we
sometimes see the clear-cut black edge of the storm’s base, but then beyond,
happily, the pleasant sight of unlimited visibility and clear sky. We become eager
to pass this line and go lower to stay “contact” and fly under. The nose is pushed
down and the airspeed goes up, so that we’re apt to start under the storm’s edge
going fast. However, under this edge will be some really rough air with hard,
sharp-edged gusts, and high speed will be dangerous. So patience is needed to
keep us slowed to turbulence-penetration speed as we sneak under this dark shelf
of storm. We should realize there’s tough flying yet to be done before our
peaceful sky is won.
In early airline days, a DC-3 was flown under such an area in a flat but highspeed dive by an overeager pilot. The jolts resulted in injury to 10 passengers and
some wrinkles in the airplane!
Dry Climate and Thunderstorms
In dry climates, like the western United States, days with a low dewpoint and hot
temperatures create very high-based cumulus clouds; assuming there is enough
moisture when temperature and dewpoint meet. It is not uncommon to see cloud
bases of 12,000 feet or higher, and one glorious soaring day heading north up the
Rio Grande Valley toward Albuquerque, New Mexico, they were 20,000 feet.
There was a bit of light snow, while a hot July day lay far below.
If there is enough moisture and instability above the cloud base, we can see
Cb develop. How dry it is below the cloud base will decide how much rain makes
it to the ground. Dry enough, and we may see nothing but a little gossamer curtain
right below cloud base called Virga, it’s evaporating precipitation. More moisture,
and there are gossamer shafts of rain reaching toward the ground. This
precipitation comes out inconsistent of time and location, which shows things are
pretty inconsistent in that cloud. The other aspect of these storms is that they can
cover a large area, spreading larger as new Cb develop.
In this virga/gossamer rain stage, it’s a bad time to go underneath. Remember,
we’re in dry climate, the gossamer rain might be what’s left from evaporation of
serious rain. Rain means the storm has matured, with cold air headed down. This
is a real setup; it’s getting ready to unleash itself, but we don’t know when or
where. In soaring events, when young and foolish, we would drift under these
developing thunderstorms, their lift quite good until they began to rain. With
flatland soaring being convective-dependent, it was an interesting education. Let’s
just say that weaving around and under these spooky shafts of rain is rolling the
dice. A great example of how fast things can change happened over the flats of
eastern New Mexico under a darkening line of building Cb. Seemingly okay,
because nothing was coming out of them, I (ROB) was climbing nicely in good
lift. Suddenly, there was a loud slap of huge raindrop splattering on the canopy,
then another, but nothing continuous. At the same time, the 800 feet per minute
thermal I was working turned to 800 feet per minute sink in less than a few
seconds. We escaped, found lift a couple of miles to the side, then flew on, but it
was a great lesson in how fast things can change; I never forgot it, and it
influenced quite a few weather decisions throughout my aviation career.
Decades later, my son and I (COB and ROB) were faced with the decision of
crossing the Sandia Mountains east of Albuquerque in our Cessna 170. A huge
thunderstorm hung over the Sandias, with clear blue over Albuquerque. We could
easily see through the few gossamer rain shafts, and even thinking back, it
seemed tempting to slide through. But the airplane was gutless in that high
country, and memories of those soaring years’ past told us we knew better. Then
my son pointed out a swath of virga, way above, white as in snow or maybe hail.
Moments later a nice zap of lightning flashed a few miles away. We turned around
and landed at Moriarty, then in sun, but by the time we’d tied down, the wind had
swapped 180° from the storm’s falling air, bringing rain then hail. The locals said
it never hailed—figures.
A great picture of a line of thunderstorms along a cold front. The “open” places
between the storms are very high and will tend to close up as other cells develop.
This isn’t a front to try VFR. It’s an instrument flying job with airborne radar
equipment required. (PHOTO COURTESY OF NOAA)
These are storms that breed microbursts, and we rarely know when they are
ready to fall, even by fiddling with radar, lightning detection or dark-magic. That
cold air and rain heads down from the cell, then spreads out as it hits the ground,
giving us that dreaded wind shear we talked about earlier. If it’s a wet microburst,
we see the rain and don’t fly into it. On the other hand, if we see dust and junk
rolling up in kind of a vortex ring, it’s a dry microburst. Either one is bad news,
especially, as said before, when landing or taking off. The problem is, if we are
there when it happens, it’s too late. There are a few danger signals that might
indicate microbursts:
Wet microbursts:
•
•
•
•
Heavy rain or lightning
Rain shaft
Strong storm outflow (wind), blowing dust and debris
Clouds with a bowl-shaped underbelly
Dry microbursts:
•
•
•
•
•
Surface temperature above approximately 24 degrees C (75 degrees F)
Temperature-dewpoint spread of 15–25 degrees C (30–50 degrees F)
Convective, high cloud bases that may also be bowl-shaped
Virga or scattered light rain
Radar returns of weak cells with high bases
These are helpful criteria, but not cast in stone. They can vary, as should our
thinking and creativity, in dealing with thunderstorms and related convective
issues.
Frontal Thunderstorms
We visualize frontal thunderstorms as part of a dark, vicious cold front moving
across the countryside with high winds, pouring rain, and much lightning, and
that’s a pretty accurate picture. But there are warm front thunderstorms too, and
they are different.
What’s the difference? Well, it’s mostly in the height of the storm’s base. A
cold front’s storm base will be close to the ground, with no room to fly under
without getting the full force of the storm. But warm frontal storm bases are
generally aloft. How far aloft will depend on the frontal slope. We’ve seen
thunderstorm bases as high as 16,000 feet, which is unusual. But I’ve seen lots at
4,000 and 6,000 feet. Between Chicago and Kansas City, Missouri, for instance,
there are often thunderstorms reported over most of the route. However, by
closely examining actual weather reports, one could see that the bases were high,
which indicated a warm front condition. A flight at 2,000 feet put the airplane in
smooth air, although there were clouds, stratus from falling rain, lots of rain, and
frightening lightning all the way.
The Surface Wind Tells
How do we learn if it’s a warm front kind of condition? First, as always, is a look
at the big picture. Where are the fronts and what kind are they? Next, a careful
study is made of the surface weather reports, with particular attention paid to
surface wind. If the storm bases are high, the surface winds will not be strong and
gusty at stations reporting thunderstorms. The wind will pretty much stay normal
for the general circulation. This is the best clue that the storm is a high-based one.
A warm front will also have storms over a large area with extensive cloud
cover. A cold front, in contrast, will show up as a line of thunderstorms and can be
seen on surface weather reports by the strong ground winds and a dramatic wind
shift as it passes a station.
A warm front is of special interest to the turboprop and light pressurized
twins, because their normal altitudes may put them near the warm front surface
aloft, where the thunderstorms are wildest. The pure jet will get on top of all this,
or up where it’s easy to dodge around, and the little guy will be lower and
probably under the thunderstorm bases.
How to Tell a Front’s Toughness
The intensity of a cold front can be learned by studying the sharpness of the wind
angle ahead of and behind the front. If the wind in advance of the front, for
example, is from about 210°, and the winds behind the front are from 340°, we
can bet that the front will be a wild one. Also, the larger a low pressure’s warm
sector, the more violent a front. The bigger the temperature difference between the
warm and cold side of the front, the tougher it will be.
It is also important to check the speed of a cold front by looking back over the
sequences to see how fast it has been moving. If it speeds up, you can bet it’s
getting stronger.
And, of course, there is our old friend orographic influence; if the front is
moving up sloping terrain, that too will make it worse.
Prefrontal Squall Lines
Cold fronts have a phenomenon associated with them that complicates the picture:
the prefrontal line squall. This is a line of thunderstorms that breaks out 100 to
300 miles ahead of a cold front. They occur mostly in the afternoon, when heating
adds to the zip of instability, along with the lifting effect of convergence in
advance of the front. All this is difficult for the day-to-day pilot to analyze; simply
always be suspicious of a prefrontal line squall when a cold front is on the move.
This squall line ahead of the front is where the toughest thunderstorms are
found. It is where most tornadoes occur. It is where most hail is found. It is a good
thing to avoid!
As a prefrontal squall line develops and intensifies, the cold front behind it
tends to diminish and sometimes can be difficult to find on the weather sequences.
As evening approaches, the prefrontal squall line will diminish, and then the real
cold front will regenerate and make itself known again. What this means is that if
we negotiate a prefrontal squall line, we may think we have finished with its
violence, but it may turn out that 300 miles along, as night approaches and we fly
toward the dark, our cold front has perked up, and we find ourselves facing
another line of thunderstorms.
A good rule of thumb is that prefrontal line squalls are generally not active
within 150 miles of a low center, nor more than 500 miles out from the center.
They show up in an area 50 to 300 miles ahead of a front and roughly parallel to
it. The breaks in a prefrontal squall line are sometimes larger than in a solid cold
front line, but this is a flimsy thing to depend on.
Some Rules
The same rules apply to cold fronts and prefrontal line squalls:
1. Flight on instruments should not be attempted unless we are equipped with
airborne radar in good working order, and with it a knowledge of how to
interpret what the radar shows. A look at NEXRAD and a lightning detection
system in advance will show how active the front is, and if there are any clear
places through it.
2. Low flight underneath should not be attempted, because of extreme turbulence
and the possibility of heavy hail.
3. The best procedures are to fly well around the line of storms or to land and
wait for it to pass. Landing isn’t too great an inconvenience. First of all, these
sharp lines of weather pass fairly quickly. Second, in a year of flying, most
pilots don’t encounter such conditions more than a few times. Of the total
year’s time flown, those rare couple of hours sitting relaxed on the ground is
well worth it.
If We Fly Through
Now, of course, comes the time when, for some hard-to-imagine reason, we barge
ahead determined to go through that cold front. Where should we take it on?
As we’ve said before, down low isn’t good. Another place to avoid is the area
where temperatures are (minus) -7 degrees C to +4 degrees C (20 degrees to 40
degrees F). Research has shown that this is the area where most lightning
discharges occur. It’s also an area where carburetor ice will be at its maximum.
A logical place to go through is just above the haze level, at the inversion.
Here there is a minimum effect from heating, and that may be a place where the
violence is a little less, and we emphasize little.
We can visualize flying toward a front. The sky is hazy and visibility poor in
the hot mugginess. Cumulus clouds dot the sky. To avoid them, see better, and be
in smooth air, we climb above the haze level. As we climb, the temperature
decreases, but just as we come up out of the haze to where the visibility is
unlimited, the temperature rises. That’s the inversion.
Now we can see the cumulus sticking up through the haze. We are over Ohio
flying at 10,000 feet. We should be updating weather along our route, which is
easy if we have data link weather, otherwise we use Flight Watch or the FSS radio
contact, noting which stations have southerly or northerly winds as an indication
of the front’s location. The wind velocity, the abruptness of the wind direction
shift, and the temperature difference across the front are checked as well, along
with the presence of thunderstorms at various stations en route.
Flying farther west we note that the tops are climbing. We are at 12,000 feet
and ahead is a line of cumulus from one end of the horizon to the other. That’s our
front.
This line of cumulus reaches very high. At first, we have hopes of topping it,
but experience says we’re kidding ourselves. The line has higher places with anvil
tops. These are the cells of the storms. With either type of radar, we can see them
and begin to plan a route through, but hopefully we’ll be using airborne radar if
we have any thoughts of picking our way through. Lightning detection would
show the hottest electrical areas, and NEXRAD the layout, but with time delay
leaving unknowns. Flying without radar, if one (incredibly) does so in this day
and age, we’ll make an educated guess.
Close to the front there will be a towering cloud wall extending to neckstretching heights. Below will be stratus and low, boiling roll clouds. At our level,
just above the haze, we’ll see some stratus and layers. The wall of the front is a
solid mass, bulbous in places; its color is eerie, anything from misty white to a
black yellowish-green, depending on the sun’s position in relation to the front.
We study the complex picture before us and try to decide how to take it on.
We don’t want to descend and try to get under that roll cloud, because the air is
wildly rough right there; it is probably the roughest part of the storm. It’s tearing
up in tremendous currents, as well as chopped up and inconsistent. Close to the
ground, the wind over the surface adds to the thunderstorm’s normal drafts.
Progressing through this roll area, we’d run into heavy rain and zero visibility.
The rain might affect our airspeed, and there are also localized pressure changes
that will affect the altimeter’s accuracy. (No one can tell you how much for
certain, but some knowledgeable researchers think it may be as much as 1,000
feet.) So let’s forget low down as a place to go through.
We look up, way up. We’ve probably studied this area for a long time as we
approached the front. What we are looking for is the lowest point in the top of the
long line of clouds, a saddle between towering Cb. When we find it, our first
tendency is to climb right up there and slide over between the Cb. But as we’ve
said, this is risky business, because just as we are approaching the saddle, the
clouds will build up in front of us and suddenly there isn’t any saddle or it’s much
higher than it looks. The risk, to repeat, is that we’ll find ourselves struggling up
high, at a mushing, high angle of attack ready for a stall. Unless we can zip over
this saddle between the Cb with good speed and control, we shouldn’t fool with it.
At Night
Finding the right place at night is more difficult, but the flashes from lightning
help. Approaching the storm area, we study the cloud structure in the briefly lit
periods as flashes occur. We can often spot the individual storms by the
concentrations of lightning. It is well to do this from as far away from the cloud
mass as possible, because close in, the origin of the lightning becomes confused
as it reflects and lights up all the clouds.
Lightning can be seen from a long way off at night, and storms that may seem
on top of you can still be 50 or 100 miles away. Close to the storm area, when
looking out, care must be taken that a nearby lightning stroke doesn’t temporarily
blind you. When you’re that close in, it’s time to have the cockpit lights up bright
and the decision made as to where to penetrate the mess.
Where to Bore In
We’ve decided that we cannot top the line anywhere. So we’ve picked a point
under the lowest place in the top of the line confronting us. We’re above the haze
level and eye-to-eye with the solar plexus of the storm.
Before barging in, we ought to study the color of the precipitation ahead. If it’s
white and fuzzy, with a gossamer look, it may be hail. If so, then we’d better
wander up and down the line some more and find another spot that looks darker,
like rain, and not whitish, like hail. Let us restate, before going into this line of
thunderstorms: WE DON’T RECOMMEND IT .
However, we have our spot picked and are about to go in. Now the problem
changes from weather judgment to flying technique.
How to Fly It
First, we prepare the airplane. We pull down on the safety belt and put on the
shoulder harness. We make certain that loose items are fastened down and
passengers well strapped in.
Put on heat for the pitot, carburetor, or jet inlets. Now, establish the airplane’s
best rough-air penetration speed and note what the power settings are for that
speed and where the stabilizer trim is set. Note the airplane’s heading.
However, we should pause here and talk a little about the penetration speed.
Basically it’s the slowest speed possible without danger of stalling. We want it
slow, so that the airplane will be in its best condition to take heavy gust loads. Too
slow, however, has proven to be almost more dangerous than too fast. As we’ve
said before, when airplanes come apart in severe turbulence, the problem begins
with loss of control, and an easy way to lose control is to stall or to get a wing
down and into a spiral dive.
Clean, swept-wing airplanes are worse in this respect than slower, straightwing airplanes. If they lose control, they gain speed quickly. A swept-wing
airplane isn’t as straightforward in its elevator-control system as a conventional
airplane, because the amount of elevator control available is dependent on the
stabilizer setting. On certain jets, pitch trim moves the whole horizontal stabilizer,
and one runs out of elevator control unless the stabilizer setting is correct. In
effect, because of the large surface area, the stabilizer is the elevator, and the
elevator is like a trim tab. A more conventional airplane doesn’t run out of control,
because the horizontal stabilizer is fixed, and the trim is what we find on, say, a
Cessna 172—the little trim tab “flying” the elevator. It just gets harder to pull or
push.
It’s best not to fly too slowly with any airplane. Most aircraft manuals
recommend the proper speed for turbulence, and it will be something like 60
percent above stall. A 100-mile-per-hour stalling airplane may have a rough
airspeed of 160 IAS. Jets may have higher speeds, but again, it’s best to consult
the airplane manual. Know your airplane’s best turbulence penetration speed; get
it from the manual.
The airspeed we’ve picked is important, but equally important is how we fly
it. What we do not want to do is chase speed with the elevator control and the
airspeed indicator. The key to rough-air flying is to maintain a level attitude and
do it by flying the artificial horizon. Note where level position on the horizon bar
is with the airplane stabilized. Then keep it there. We do this with gentle pressures
and not big pushes and heaves. Airspeed will vary, often wildly, and if we attempt
to chase it by pushing or pulling, we’ll soon get into some pretty extreme
attitudes. The trim and power settings should not be moved to any large degree.
The proper pitch attitude, power setting, and stabilizer position are important
to know in advance, so one can set these up quickly and not fight an out-of-trim
airplane while trying to settle down to the proper airspeed and power setting.
These settings should be learned, as we’ve said, on a clear day, by trying them for
various altitudes and weight conditions. But the best insurance is to get down to
turbulence-penetration speed, power setting, trim, and attitude before one enters a
turbulent area. Of course, there are times when we hit turbulence unexpectedly;
that’s why the clear-air experimentation is useful to give us guidelines to shoot for
when things are suddenly wild!
We have to face the fact that it is difficult, often impossible, and generally
undesirable to maintain a given altitude when flying through the business part of a
thunderstorm, ATC or no. Of course, we try to maintain the proper altitude, but
only as long as it doesn’t require appreciable power or attitude changes. Too
diligent an attempt to maintain altitude will result in the extreme attitudes and/or
power changes that lead down the path to loss of control.
Are We Scared?
A thunderstorm line is a pretty awesome sight. It’s scary, and any honest pilot, no
matter how experienced, will tell you so. This fear is a factor to consider.
We’ve mentioned that, scared or not, a weather-flying pilot has to control
emotions and keep imagination subdued or use it only to advantage. The pilot has
to fly carefully and thoughtfully, even though scared to a knee-knocking state.
The toughest place to keep this fear under control is in a thunderstorm. It is
dark, it is turbulent, rain comes down in a deluge, lightning flashes close,
sometimes we can hear thunder, and occasionally we smell ozone from a nearby
lightning passage. A lightning discharge may make a brilliant flash and loud bang.
An irritating, hashy noise may be tearing at our eardrums from static in the radio.
It’s a hell of a place for anyone to be! It takes a strong will to say, “I’ll watch the
horizon and keep it level. I’ll hold that heading, keep the wings level, and it will
all turn out okay.” But that’s it, and the only way to do it.
To help our situation, we should have the cockpit lights turned up full bright.
If a lightning strike occurs, this will prevent temporary blindness. We should drop
the seat as low as possible and keep our eyes inside the cockpit for the same
reason. Bright lights and a low eye level help protect from a blinding flash, and
they help psychologically, too. The bright cockpit lights keep us from seeing out,
as does the lowered seat, and this helps shut out the terror. It puts a “protective”
barrier between us and that awful world out there. It’s a phony barrier, to be sure,
but if it helps subdue panic, who cares?
So we come closer to the actual clouds. The first thing that makes us feel
something’s about to happen will be a strong updraft. It probably will be smooth
but powerful. The airplane wants to go up, and if we push ahead to maintain
altitude, the airspeed will also go up. We can pull power to keep the speed low,
but then the engines may cool so there won’t be enough heat for carburetor or jet
inlet anti-icing. If we don’t pull power, then we get a nose-high attitude that’s
undesirable. We are probably best off leaving the power set at our best rough
airspeed setting, keeping the horizon on the position of pitch for level flight, and
the devil with altitude. If we are using an autopilot, the altitude hold may want to
be off and the airspeed hold, if there is one, should definitely be off. The human
pilot should keep the nose on the horizon bar with the manual control. The
autopilot will only be doing the heading and lateral work, which is a help and
important, but it is stupid in its handling of altitude–attitude–airspeed
relationships. (Older autopilots were more of a problem in the altitude hold
situation, but newer ones can be much better. Auto throttles can cause excessive
pitch changes, especially with engines mounted on the wings, so it may be best to
deactivate them as well. However, we want to consult the aircraft manual on the
recommended autopilot/ turbulence procedures, as well as try it on a turbulent,
VFR day. This knowledge may be important in many turbulence situations.)
Whether we’re on autopilot or hand-flying, the wings should be held as level
as possible, even if it takes big aileron movements and a lot of work. Nonlevel
wings hurt speed control, because an airplane wants to descend when it’s banked,
and level wings help to keep us going straight. The last thing we want to do in a
thunderstorm is wander. We start in with a heading that we feel is the shortest way
through, and then hold it tight to quickly get through.
The biggest updrafts occur outside the cloud. Rain hasn’t started, but we don’t
like the feel of the updraft, because we know that when it stops, there’s going to
be a jolt. Then, just as we start into the cloud, our updraft stops with a jolt, and the
air becomes very turbulent. Side gusts, downdrafts, updrafts … it’s wild. It’s dark,
and as the airplane is jolted and jarred, heaved up and squashed down, the rain
begins with slaps of big drops at first, then, suddenly, inundation. The rain flows
over the windshield like a river, and it is noisy. Most people would say it is hail.
There may be soft hail, and it may make a frightening noise, but it isn’t big, solid
hail. Solid hail is a noise to end all noises. It’s unforgettable, tremendous, and no
one ever mistakes it for heavy rain once they’ve heard it.
And what if it is hail? There isn’t much to do. Keep a firmer grip on emotions,
but above all hold the heading! Hail is confined to a small area. Turning back will
probably result in a longer time in the hail. Also, a turn will expose the side of the
airplane and break out windows. In years past, when even large aircraft had
fabric-covered control surfaces, the amount of up-elevator needed for the turn
may have exposed enough fabric to tear it open.
I (RNB) saw a DC-3 once that had flown into heavy hail in Kansas, and the
pilot had turned around. I looked at the airplane as it sat in the hangar, a battlescarred wreck. The leading edges were beaten in, the landing lights broken out,
and the windshield, too. But most interesting was that every window on one side
was broken! Fortunately, it was a cargo flight without passengers. The fabriccovered elevators had numerous rips and slashes. So don’t turn around in hail.
There are some interesting points about hail. Most of it in the United States
occurs between the Mississippi River and the Continental Divide. April, May, and
June are the worst months, and the worst time of day is between 2 p.m. and 10
p.m. Cold front and prefrontal thunderstorms are more apt to have hail than airmass thunderstorms.
Hail forms in the storm’s building stage and falls when it’s in the mature stage.
It is largest near the freezing level. Flight well above or well below the zerodegree C point decreases the risk.
Looking again at the tropopause and thunderstorm heights will give a clue to
the possibility of hail. If the radar reported storm tops pushing up above the trop
by 5,000 feet, one can expect to find at least ½-inch hail.
In the black, heavy rain, the turbulence keeps up, but there is a feeling that it is
diminishing. It’s still wild and rough, but we feel more in control of the situation.
There was probably a point in the early part when it was so rough that we doubted
our ability to keep control if it got any worse. Now, in heavy rain, we feel that the
out-of-control threshold has been lowered in our favor. The rain does dampen the
turbulence to some degree.
Something to Be Said for Rain
There was a time, before radar, when pilots said that if you must go through a
thunderstorm, pick the blackest part with the most rain. When radar arrived, this
became taboo, and we learned the error. The reason, of course, is that radar shows
where a cell is by reflecting from the rain. So radar says, “There’s the heavy rain,
that’s the storm’s cell. Avoid it!” This is essentially correct. But the most severe
turbulence isn’t exactly in the middle of the rain. It’s close by, however, and if you
miss the rain area by a good margin, you’ll probably miss the worst of the
turbulence.
Don’t be sold on the idea that the center of the rain is the wildest part of the
storm, although it may have the most violent downdrafts or microbursts as they
are called today. The roughest place is probably in the area just ahead of the
storm, near the roll clouds, before you go on instruments.
Fly!
Now, back to the storm. Our job is a simple one, really: just fly the airplane. Fly
attitude; keep it level and under control. We need a certain attention to the engines
to make certain the carburetor heat is sufficient and that they are not icing. With
injected piston engines, we’ll be considering alternate air sources. There’s little
navigation to do. We can glance at our course and try to stay with it or consider
radar deviations, but realistically, we shouldn’t do any excessive squirming,
especially with large bank angles. It isn’t going to be far enough through the
roughest part to make much of a difference.
Electrical Discharge
Lightning will flash in this darkness, and some of it seems close. The sky is lit up
for moments, and its brightness is scary. Between flashes, when it’s dark, we can
see small flicks of fire-like miniature lightning dance across the windshield, and a
quick peek at the propellers, if we have them, shows a neon-like band circling
their tips. This is Saint Elmo’s fire, more formally called corona discharge. It
means that the airplane has been flying through electrical fields, absorbed energy,
and is charged. If it collects enough charge and passes through an area in the
storm that has a big charge of opposite polarity, the energy may jump between
airplane and cloud in a type of lightning.
It goes off with a loud banging plop and a brilliant flash of light. If you were
looking out you’d be temporarily blinded, but looking in or out, it will scare you.
It’s over in a second, and we are surprised to note that the airplane still flies,
and the wings haven’t fallen off. If we could see the damage, we’d probably find a
half-dollar-sized hole near the wingtip or at the tail cone or in some other smallradius area. The side of the fuselage might have very tiny, rough, bubbly
imperfections, as though it was partially melted; it was! A radio may have been
damaged, and we should look with suspicion at the magnetic compass. In some
aircraft a generator/alternator may have fallen off-line, so that may need resetting;
usually it comes back. What happens to electronic displays is potentially varied,
but usually they are fine. However, this is a great example of when the glasscockpit and autopilot-dependent pilot may quickly need to hand-fly raw data from
a small standby horizon or, hopefully not, a turn coordinator; if this happens in all
the turbulence, we don’t have time to fiddle and troubleshoot, instead we just fly
until we’re out and all calms down. Beyond this we are okay. Thousands of these
discharges have occurred with few serious results, except as noted in the
beginning of this chapter.
These are commonly called lightning strikes. They are the only kind an
airplane gets. Airplanes aren’t “hit” by lightning as we visualize a person on the
ground being hit. There is always an electrical discharge between airplane and
cloud. A person on the ground, actually, isn’t really “hit” either, but is a point
where electrical potential jumps from earth to cloud through the person. Though
we always think of being “struck by lightning,” the person “struck” is a part of the
process of discharge.
The chances of a discharge can be lessened, as we said, by staying out of a
temperature region that is 4° degrees C either side of freezing. The majority of
discharges happen where the precipitation is rain mixed with wet snow. There are
little tricks, too, that may help; they certainly will not do any harm. One is to turn
on propeller alcohol/deicing fluid, if available; another is to flick the mike button
now and then. What these two things may do is help carry away part of the energy
that’s been built up on the airplane. It’s a slim possibility, but may be just enough
to keep the charge below the critical point. The important thing, however, is to
stay away from the freezing-temperature area. Incidentally, the faster the airplane,
the more likely we will get a discharge. Also, while keeping away from the
freezing level is best, it’s not a guarantee. The discharge I (RNB) had out of
London, resulting in that big piece being torn out of the 707 radome, occurred
between two cumulus whose tops were only 11,000 feet at a temperature of 14
degrees C.
The electrical charges come in two ways, and they are worth talking about.
One we have explained: accumulation of charge caused by flying through
electrical fields. These are huge, with tremendous voltages, and are part of the
thunderstorm instability process. I always visualize thunderstorms as big
waterfalls of electrical energy; you fly through them, and the airplane is covered
by the energy, of which a great quantity is absorbed. The other kind of charge
arises from flying through precipitation. This, crudely, is a friction process, like
the crackling one hears when combing one’s hair with a plastic comb on a dry day.
This type of charging doesn’t affect things nearly as much as the field type.
It’s easy to see that when flying through a thunderstorm we get the field-type
charge, and if we are flying in the wet snow area, we also get the friction type in
its worst form, so we are getting the maximum. Getting away from wet snow
deducts part of the charge—unfortunately the smaller part.
Static and Radio
All this charging causes static, which knocks out radio reception on certain
frequencies. Fortunately, it rarely affects reception in the VHF ranges. It offends
most seriously in High Frequency (HF ) frequencies used in long-range
communications, as well as the ADF 200–400 kilohertz range, for those who still
have ADFs.
An electrical charge looks for the easiest way off the airplane. This will be any
small area, like a copper antenna wire. Of course, when the charge bleeds off an
antenna, it makes a terrible noise in the radio. Although long-wire antennas are
pretty much things of the past, the solution was to use a large wire with a
polyethylene coating, the entire thing being about the diameter of a pencil. Also,
the insulators and attachment hardware are large and smooth so that no wire end
sticks out in the air. The big wire and smooth insulators discourage discharge, but
this was impractical for smaller aircraft and, as said, are today more of historical
fact than use.
The other part of antistatic hardware is the little wicks we see sticking out
from the wing, stabilizer, the rudder, and sometimes, the tail cone. Today, some
are less similar to wicks and more like little prongs. These are designed as a place
where the charge can bleed off quietly and easily.
All this helps, but only for the “friction” type of charging; it doesn’t impress
the electrical-field type of charge at all, because the charge is so big the wicks
cannot bleed it off, nor could large-diameter wire antennas when they were in
vogue. If they could, we’d never have a big-bang discharge.
This was a major problem in the low-frequency, radio-range, and HF days.
The issue is now much less of a problem because of VHF, but electrical fields are
so strong, at times even VHF will start to howl and squeal in thunderstorm
conditions. It generally doesn’t last long, but when you hear it, a discharge may
occur. For long-range airplanes needing HF for communication, precipitation
static discharge can be a problem.
The ADF is becoming somewhat extinct, but where it is still used, we need to
remember it will be knocked out by precipitation static, with ADF bearings
becoming unreliable. Following an ADF indication could easily take one off
course and perhaps set up a dangerous situation, particularly in mountainous
areas. We should look at all ADF bearings with much suspicion when flying with
excessive static.
The Noise Is Annoying
While we are tossing around in the dark, wet, and rough inside a storm, we can
use radio noise in a couple of ways. If we have HF frequencies, or are using low
frequencies, the noise will be so continuous and loud that nothing else will be
heard. At that point, all the radio is doing is aggravating our condition of
apprehension. The best thing to do is to turn it off. It’s surprising how calm things
become, even in the turbulence, to suddenly have that infernal noise go away.
If we are using VHF, we leave it on. The occasional squeaking noise we hear
may tell us a discharge is close. While at this point we cannot do much about it, it
will at least have us prepared and not so startled when the bang and flash occur.
Squinting, clenching your teeth, and pressing the mic button are about all you can
do.
Almost through the Storm
As we continue, the rain slackens, the turbulence quiets down, and patches of
lightness bring encouragement. We may fly out of the storm quite quickly and
dramatically, finding ourselves in brilliant sunshine. While we breathe a sigh of
relief, it’s a good idea to remain fastened down and alert until well away from the
area.
We have traversed this storm from front to back. The worst part was first,
because the roughest part is the front, or leading part, of a storm.
Had we been coming the other way, the sequence would be reversed. The rain
would begin, and turbulence would start; it would become darker and darker, and
the rain and turbulence would become heavier. Toward the front side, light spots
would appear, but it is then that we’d get the real rough stuff, that wild updraft and
turbulence even after we have broken out of the clouds. Flying back to front, we
want to be well through and ahead of the front before we relax.
Now, suppose we are flying a jet and hit all this up high, at 25,000 or 30,000
feet. What’s up there? Lots of snow, for one thing, and turbulence, probably not as
rough as down lower, but still very rough. There is more chance for hail, and
electrical discharge—lightning—is quite possible. The massive amounts of snow,
some of it in the form of very large flakes, may cause icing, especially inside
warmer intakes, where the snow is melted only to refreeze later in a colder area.
In jets, we might inadvertently clip thunderstorms if we have been flying in cirrus
cloud, which sometimes is from thunderstorm blow-off. Yes, we are not supposed
to do that, but if, for example, we are crossing the Rocky Mountains on a later
summer day, there can be thunderstorms and blow-off just about everywhere.
With no rain up high, we have to tilt our airborne radar down low, at the same
time trying to find storms by shadows on the radar screen displayed behind the
storms, as ground clutter in mountains makes things difficult. NEXRAD gives us
good idea, but not without figuring delay and possible terrain issues. Lightning
detection, if onboard, may be our indication. The best deal is keep glancing
outside, looking for the bulges of tops through breaks in the cirrus. Eventually
we’ll nick something, but unless we are hanging on up too high, it’s a brief period
of pretty good bouncing around, and that’s it. In these conditions, it’s a good idea
to have everyone seated with their belts on; maybe the engine anti-ice on too, all
just in case. By the way, turning engine anti-ice on will reduce our power, and
hence our altitude capability.
While doing thunderstorm research, I (RNB) barged into one at 35,000 feet in
a B-17. It was impressively rough, but most impressive was the size of the
precipitation. The snow looked like big snowballs being thrown at us. This stuff
got into the intakes, clogged them up, and, by restricting the airflow, caused
supercharger ducts to squeeze in. The result was four very weak and helpless
engines and a big, not-so-good glider! Fortunately, the high altitude made it
possible to glide away from the storm, get lower, and reorganize things so that we
could limp to an airport.
Up high or down low, a thunderstorm is potent. Even over the top of one, as
mentioned earlier, turbulence will extend upward into the clear air a few thousand
feet.
Warm Front Thunderstorms
When flying warm fronts, we will be on instruments most of the time, and it will
be difficult to see individual storms. Occasionally, the airplane will break out
between layers, and then it may be possible to see the Cb towering up from the
bottom layer into the higher layer.
Because we cannot tell, without radar, where the storms are in a warm front,
we should be prepared to fly into a thunderstorm at any time. And while they may
seem a little less violent, they are still thunderstorms and can be as rough as any.
Low Down
The best rule, in warm front conditions, is to fly low. Keep down, near the
minimum instrument altitude. Because we are dealing with turbulence, it’s best
not to fly too low, and we personally prefer 2,000 feet above minimum instrument
altitude. This is dependent on terrain. If it’s all flat, we’d feel secure 2,000 feet
above the ground, but in mountainous areas, we want more.
This low flying in warm front thunderstorms is due to the fact that warm front
thunderstorms generally have high bases. The air has to crawl up the warm front
to have enough lifting to set off the thunderstorm.
If we are flying a jet, we don’t fly at 2,000 or 4,000, although I’ve known of
this being done with considerable success—if fuel isn’t a problem. With its highaltitude capability, a jet will sometimes top an entire warm front—over the ocean,
most certainly. But if a warm front with thunderstorms cannot be topped, then it’s
best to come down to an altitude where the airplane is flying well and to use
airborne radar for sneaking through it. The best altitude will depend on the jet’s
performance; generally speaking, about 33,000 feet is good. At high altitude, the
storms seem more widely spaced and easier to weave through. If you’re in a highflying corporate jet, you may just be above it all. Have a nice day.
Thunderstorms as We Arrive and Land
Sometimes we are faced with the problem of our destination being covered by a
thunderstorm or having them so close that they affect our landing. What do we
do?
First, we must approach the area and dodge any cells near the airport. We can
do this by VFR procedures if we can see, or preferably by airborne radar. The
complication, of course, is ATC. If we wander around dodging storms, we have to
keep ATC advised and get their approval prior to commencing our weaving
around the weather. It’s only logical that two airplanes from opposite directions
might be headed for the same good area. A deviation might also put us on another
airway or arrival route, which will then put restriction on how far ATC might let
us deviate.
ATC will sometimes help lead one through a thunderstorm area. This can be a
mixed blessing, but as mentioned earlier, ATC’s weather radar abilities have
improved. We recall that ATC’s primary job is to separate aircraft, so if they are
busy, they may not have time to help as much as they’d like.
The best plan is to ask the controller, before entering an area where we may
need weather avoidance, if they have time to assist us. If not, then we need to
decide if we can adequately and prudently do this ourselves, whether visually or
with whatever thunderstorm avoidance devices we have: airborne radar,
NEXRAD and/or lightning detection. Again, if the thunderstorm situation is no
worse than a few isolated cells, we might consider continuing. The best would be
that arrangement of airborne radar supplemented with NEXRAD and/or a
lightning detection system. If at any time on the arrival we risk losing path to
escape the weather area, we had best consider turning around right then.
Otherwise, there is a good chance we may have to fly through a thunderstorm!
Suppose we made all the conservative decisions, but still got stuck in a tight
avoidance situation with a lightning detection system or NEXRAD. We have to
remember limitations of no precipitation indication (heavy rain, micro-bursts,
hail) if only using lightning detection, or the time delay issue with NEXRAD;
base or composite scan knowledge can be helpful as to the cell potential. If we
have airborne radar, we should be competent in using it to the fullest, otherwise it
might make things worse. And what if we have nothing to help us? Well,
hopefully ATC can help out, otherwise we are walking blindfold in a forest.
If we are dealing with frontal, squall line, or severe weather, we shouldn’t be
there anyway, and hopefully we have kept open an avenue for breaking off the
arrival and going somewhere else. Lastly, all this deviating as we approach an
airport is one thing, but when we get there and the airport is under or near raining
Cb, or under ones that look just about ready to let loose, hopefully we have not
cornered ourselves in the weather so we can’t land or escape the area. We need to
be the judge—and boss!
Don’t Race Thunderstorms
A real hazard is a pilot trying to beat a thunderstorm to the airport. There’s
nothing wrong with trying to get there first, but there are a couple of possible
pitfalls. One is diving and allowing the airspeed to get too high, and then suddenly
flying into the rough area just ahead of the storm at this high speed. Another is
racing to get to the field and then landing as the storm arrives, or even when it’s 5
or 10 miles from the airport. The wind shifts abruptly with gusty force, and a
cross-tailwind suddenly makes landing difficult, perhaps impossible. This, again,
is where severe shear occurs.
With the wind shift comes heavy rain that obstructs all vision, and one may
suddenly go completely on instruments—zero-zero—anywhere along the
approach. At 100 feet, for example, the pilot will suddenly be unable to see the
ground. Even if the rain arrives just at touchdown, the visibility will be so poor
that it will take luck to make a straight runout and stay on the runway. It’s a
terrific shock to suddenly learn how bad visibility is in heavy rain. Braking will be
poor, possibly nil, on the wet runway. The airplane can hydroplane and not stop.
With a strong crosswind, it can also slide off the runway sideways. And always
remember that thunderstorms on or near airports are the classic recipe for shear
accidents.
Maybe a fair rule of thumb: if we have to either land in, risk landing in, or
pass through on approach any heavy rain areas, especially when we are unable to
see through it, we should discontinue the approach or landing, stay out of the
weather, and go somewhere else.
Missed Approach In Thunderstorms
Now, an important point. Let’s say we are racing a line of thunderstorms to an
airport. The line arrives just as we do. We decided to pull up and abort the
landing, because it is impossible. Now, which way shall we turn, right or left? In
the northern hemisphere it’s best to turn right. Why?
The wind has probably changed to northwest. Making a left turn, we will have
a momentary drop in airspeed, bringing us closer to stall; the sudden, new, side
component of wind will also tend to overbank the airplane; an intense downdraft
will be present as the cold air arrives. It all spells an airspeed loss that’s difficult
to regain. There have been accidents that were caused by loss of control when
turning away from a thunderstorm.
Of course, if you are still in the southerly wind part of the approaching storm,
you’d best turn left. The point we are trying to make is that if you get in close to a
storm, particularly where the rain has started and the wind has shifted, then decide
to turn around and get out, it is best to make a right turn.
Another variation worth watching is an isolated cell near an airport, yet to
rain. The wind very likely will favor going toward the cell; it is being sucked in.
However, when the rain begins, it will spread out as it hits the ground, just like a
microburst, even if not a classic, full-fledged one, with the wind now rushing
away from the storm, totally opposite from before the rain.
In smaller sense, a good soaring sky full of fair weather cu is susceptible to
this same event, usually of smaller magnitude, but nevertheless worthy of
mention, as a wind swap may affect our aircraft’s performance. That’s why it is
important to look not only at the windsock, but the sky as well.
There isn’t always time or circumstances to do the correct thing, but right or
left, remember the air will be gusty and shifty, and it’s very important to maintain
enough airspeed above stall to take care of downdrafts and wind shears. If power
is needed to accelerate the airplane, this isn’t a time to be bashful about the
amount. Pour it on, lots of it. It takes an airplane longer than you think to gain
airspeed by power alone when pulling out of a low-airspeed condition.
After the Missed Approach and Other Thoughts
When we have hopefully made that missed approach and are away from the
storm, what then? If it’s an air-mass storm, we may want to hold out in a clear
area until it leaves our airport, and then go in and land. If it’s a front, we’ll have to
pass through it before we can get to our airport. This case calls for a retreat to
some still-clear airport where we can land and wait until the front has passed.
Then we fire up and complete the flight calmly and pleasantly.
Let’s say we have put ourselves in a pickle, either on this missed approach or
flying anywhere around a thunderstorm area, and find ourselves boxed in, unable
to escape getting into the storms. If we’re flying a light aircraft, and especially
without the capability to fly in such conditions, it maybe time to swallow our
pride and consider an off-airport landing, just as was mentioned in the VFR
chapter. In hopes we have given ourselves time, we look over our landing spot,
plan the approach, and methodically fly to landing. Even if we ding our bird, it’s
better than losing it in a thunderstorm.
Once you get on the ground, no matter where you are, give careful
consideration to running around the airport in the middle of a thunderstorm. Years
ago, two aspiring, aviation-loving young fellows ran to tie down an aircraft in a
thunderstorm. They were struck and killed by lightning. Aircraft are expensive,
but hardly worth that much.
In summary, the first thing in any airplane at any time is to stay out of
thunderstorms! If you must fly through fronts or heavy cloud cover that contains
hidden thunderstorms, don’t do it without radar and/or a lightning detection
system. If the radar fails while you’re in the middle of the mess, or for some other
reason you get caught, fly the best speed, fly attitude, and hold a heading.
Remember power settings and stabilizer settings, so if excessive dives, climbs, or
upsets occur, you’ll know where things ought to be for the best chance of flying
through the situation. Don’t fly very low or very high! And most importantly,
keep emotions under control—fly smoothly and coolly.
16
Ice and Flying It
What’s it like when an airplane picks up ice? It begins by forming on little corners
of the windshield, and on the wing we see a polished look at the leading edge, if
it’s clear ice, or a fine line of white, if it’s rime. If the windshield isn’t heated, a
smear of ice will cover it. Ice will begin to accumulate on pieces of the cowling,
antenna masts that stick out, and other un-deiced places.
When icing conditions are possible, and before getting into ice, an aware pilot
knows what the indicated airspeed (IAS) should be and the right power settings
for it, whether we’re flying a propeller or jet airplane. Then, once in ice, these
settings are observed carefully for any changes. Change in IAS is a sure way to
know the ice is affecting the aircraft, and power changes say engine heat had
better be applied quickly.
However, the all-important point is that at this early stage of ice accumulation
—right now—a pilot should work to get out of the condition! Don’t cruise along
hoping for better or grind around in a holding pattern. Let ATC know immediately
that you want out. Get a different altitude. Go down if there are above-freezing
temperatures below. Get on top if you know where the tops are.
Be careful about climbing, however, if we don’t know what’s up there. If it’s a
warm front condition, we can climb into worse conditions and climbing along the
slope of a warm front is really asking for a load of ice. As a rough rule, we climb
in a cold front and descend in a warm front, but this is variable. Each weather
condition should be analyzed and studied by the pilot before deciding what to do.
Unfortunately, we cannot make hard-and-fast rules about each weather
condition. We know things in a general sense, but have to look at the flight as an
entity, with all the parts that may affect the outcome: preflight weather study, fuel
remaining, terrain below, availability of places to land—the entire jigsaw puzzle
of flight, with each part influencing the decision of what to do.
Fortunately, fronts take up a relatively small portion of our weather time. The
lesser weather, such as air-mass conditions, makes up most of it. We can come
closer to rules for flying in these conditions, and they are covered in various
places in this book.
Let’s imagine we got into ice and didn’t do anything about it, but instead just
sat there and let it grow. We would begin to see an airspeed drop. This is always a
little alarming. A couple of knots doesn’t impress us much. Five knots begins to,
and when ten knots have gone we get edgy.
The thing to do is pour on more power. We want to keep the airplane at as low
an angle of attack as possible. We don’t want to get in a tail-draggy situation, with
higher drag and ice forming back under the wing.
If we do not see much or any ice on the wings and can see our stabilizer
leading edge, it may already have a nice buildup. That’s because the aerodynamics
of surfaces that are thinner, and have a sharper leading edge, build ice earlier and
quicker. Beyond our tail, think antennas, streamlined landing gear legs, and
propellers, too.
About the time our airspeed loss is bothering us, we develop a bad vibration.
It is a hunk of ice breaking loose from the propeller. We check to make sure the
propeller heat or fluid is functioning properly. If our airplane has fluid anti-ice
with a variable flow, we’d want it on the highest rate.
Now another vibration begins. The unheated windshield gets a thicker coating,
and we can’t see ahead at all. On the corner of the windshield a big hunk of ice
has built straight ahead into the airstream, and it’s four to six inches thick! The
vibration gets worse, and now a howling starts. The howling is probably an
antenna mast vibrating from ice, disturbing the airflow around it.
The wing is going to have a good coating, so hopefully the airplane has a
deice or anti-ice system, which should be in operation. With deice boots, we have
them working as recommended for our aircraft; some systems use manual
actuation, while others apply multiple actuation through timed sequences. The ice
may break off in chunks, leaving pieces that sit in the airstream and go up and
down with the boots. We watch the leading edge, hoping the chunks go away with
further actuations. A fluid anti-ice system should be weeping over the wing at the
maximum level needed to remove the ice we have. A heated leading-edge surface
system should be on and hot.
The engine cowls of a propeller aircraft now have a large coating of ice on
their leading edges. The scoops have ice around their openings. The propellers
periodically heave off hunks of ice and the vibration increases. The antenna mast
howls and shakes.
With boots, the removal may not be so efficient, and the wing can have more
ice, so we try the boots again, or if we have a good automatic system let it keep
the boots pulsating. An anti-ice system of fluid or hot wing should have things
cleaner, but if the ice becomes severe, we are reaching the limits of a certified
system. Boots may see hunks break off, but some hunks don’t, and there’s a
messy collection of ice pieces behind the boots. The airspeed has dropped more,
and we apply more power, resetting the carburetor heat as we do. The throttle is
open an alarming amount. The ice on the engine cowls is almost out to the props.
The vibrating and howling from masts is eerie, and then it suddenly stops. So does
one of our radios. The antenna mast has been carried away.
A radio mast, about 12 inches high, loaded with drag-causing ice. Where some
antennas can be deiced, not all are, like this one. The more of these “ice
catchers” on an airplane, the less time one can stay in ice—ice-protected or not.
(NOAA PHOTO)
The wing boots are only doing a partial job, and bigger hunks of ice go up and
down with the boots. The airspeed continues to decrease, and the throttle is wide
open. The only way we can maintain speed is by losing altitude. The only way out
of this mess is down, and we hope there are above-freezing temperatures down
there, before we get to the ground. The situation is pretty desperate, but was
unnecessary, if we had done something about getting out of the ice when that little
bit first formed on the windshield corner.
Ice affects the flying qualities and characteristics of an airplane. The most
serious thing it does is destroy smooth flow and make a different airplane of the
one we know. The weight of ice is of secondary importance.
Ice affects the wing section. It affects the propeller in the same fashion. It
collects on things sticking out that create parasite drag like antennas, wires,
landing gears, and cowlings, which creates more drag. Even with relatively clean,
deiced or anti-iced flying surfaces and propellers, if enough stuff sticking out that
isn’t clean, it turns into an anchor. Drag of these unprotected areas can increase
certain aircrafts’ total drag over 30 percent.
Ice will also cause an object like an antenna mast to vibrate and howl severely
and finally to break off, or half off, which may be worse. The first experience I
(RNB) ever had with ice was in the early 1930s, flying my Pitcairn Mailwing
biplane. Cockily, with a newly learned ability to fly instruments, I barged into a
large midwinter cu. In a few moments, I had an appreciable load of ice. It
collected on the wires that held the wings on. The wires started to vibrate wildly
up and down at least a foot each way. I expected them to break at any instant. I
didn’t have a parachute. I quickly flew out of the cu, the ice shook off, and the
wires didn’t break. I had become much older and wiser.
My next serious ice experience was in the early 1950s during the heyday of
the big piston-engine airliners, which involved flying a Lockheed Constellation
across the North Atlantic. At 18,000 feet, I encountered light ice, which covered a
long, thick wire antenna that went from a mast up front to one of the three fins at
the tail. The antenna vibrated and finally broke near the fin. The long wire, with a
big antistatic insulator on the end, whipped around and kept beating against the
fuselage. I tried different airspeeds in the hope that the wire would “fly” out
straight and stop beating the fuselage. Nothing helped and finally the insulator
gave a sound whack to a window, breaking the outer pane; fortunately there were
two panes. But this meant reducing the cabin pressure and descending. The
descent took us into a worse icing condition. It was a moment of relief when we
finally landed at Gander, Newfoundland.
The point is that often the gadgets on the airplane are the worst offenders. If a
pilot expects to fly a lot of weather, the airplane should be as clean as possible,
with a minimum amount of stuff sticking out.
Flying a 747 or any jet leaves little ice and none of the howling, vibrating stuff
from gadgets that collect ice. The jets are “clean” airplanes and the “cleanness”
reflects in their resistance to icing. There’s also a temperature rise over a jet’s
surfaces, due to ram air at their high speed, but that’s another story, and certainly
not an issue for our general aviation operations down low and in the weather.
However, jets have to land and takeoff just like every airplane, and in severe
icing, a jet operation still needs to be concerned, despite their efficient heated
anti-icing systems.
Most important is that no matter what we are flying, we must realize that
deicing or anti-icing equipment does not allow us to fly indefinitely in ice. It
cannot do this job for all conditions. It will help and give us time to work out of
icing situations, but it will not allow us to sit there all day long. There are a lot of
reasons why it isn’t good enough, and one of the main ones is that deicing
equipment doesn’t cover the entire airplane. Another is that it doesn’t completely
clean off all the ice.
So we have an important first rule: When ice is encountered, immediately start
working to get out of it. Generally this means a different altitude, after a request
to ATC. Unless the condition is freezing rain, it rarely requires fast action, and
certainly never panic action, but it does call for immediate, positive action.
About Ice
Now let’s talk about ice in detail. First, there are officially three kinds: clear, rime,
and mixed, but the latter is a combination of the primary two: clear and rime.
They are what they sound like. Clear ice is a smooth, hugging type that is tough.
Rime is crystal-like and pretty. When it forms in windshield corners or other
places where airflow patterns change, it takes on weird shapes and sometimes
sticks out ahead as long cones into the airstream. Rime ice breaks off fairly easily
with deicer boots that pump up and down. Anti-ice systems of heat or fluid should
be actuated when we expect ice or when it initially begins, theoretically keeping it
from building up in the first place.
Clear ice doesn’t always break off with boots, and one difference between
rime and clear is that clear ice cannot be as easily removed by deicer boots as
rime can. This is an oversimplification, however, as other problems can develop
on unprotected surfaces, which we’ll talk about further in the chapter.
Ice comes in four classes: trace, light, moderate, and severe. These are difficult
classifications that depend on the pilot’s judgment; one person may think a certain
degree of icing is light, while another calls it severe. Even aircraft that are FAAcertified for “Flight Into Known Icing Conditions” (FIKI) reach a point where the
system can’t defeat the ice. That starts at the severe category, but again, it is not
easy to determine what sort of ice we’re in. If our aircraft is not FIKI-approved,
our plan should be to depart into conditions where we can stay out of ice. Modern
forecasting is getting better, but still the sky is full of changing pockets and
altitude levels of various moisture and temperature variations, making total
forecasting accuracy impossible. Consequently, in a sky with potential ice
ingredients, we have to assume it will happen, despite what a forecast says, and
have workable alternatives in our bag of tricks or don’t take off.
Generally speaking, the categories refer to the rate at which ice forms. In
flying through freezing rain, ice accumulates very quickly and is called severe.
Because it’s rain, it has to be falling from an area warm enough to have water.
The cue in freezing rain is to climb. If our equipment and aircraft ability is
limited, then it’s best to quickly turn back or land. At any rate, we must do
something fast, because it forms fast!
I (RNB) remember a DC-2, flown by a friend, approaching Chicago’s
Midway. At the McCool Beacon, about 30 miles southeast of Midway Airport, he
ran into freezing rain. Midway seemed so close he decided to make a run for it.
He landed with almost full power dragging him in. There was so much ice on the
airplane that it was necessary to chip it off the fuselage to get the door open! A
few more minutes, and he would have spun in. This was during the time, before
we knew better; when we thought a DC-2 could fly through any weather. We
learned differently.
In retrospect, many of these clear ice episodes of the past may have been what
we call today Supercooled Large Droplets (SLD ). These supercooled droplets of
drizzle and freezing rain can range beyond 500 microns in diameter, give or take
ten times the diameter of a previously considered 50-micron maximum that was
considered the biggest problem relating to icing accidents. This really didn’t come
into operational consideration until the investigation of a fatal regional airline
icing accident in 1994, also south of Chicago, which confirmed that the larger
droplet issue was a problem. These larger droplets were always up there, but when
droplet measurement research took place in the 1940s, the device used for
measurement could not pick-up SLD-sized droplets. Scientists knew these larger
droplets were up there, and a few worried about it, but the concerns were
ultimately brushed aside as minimal, especially from not fully understanding how
SLD formed on an aircraft. SLD is, in comparison to all icing issues, still a
minority of icing-related accidents, but it’s not a minority problem if we’re the
ones in serious trouble!
There is a lot of available information on SLD that, as pilots, we need to
understand; NASA’s SLD and In-Flight Icing Training media (reference this
book’s suggested reading section) is our recommended viewing for understanding,
recognizing, and dealing with these icing issues. There’s a lot of excellent,
devoted work in those tutorials. The reason SLD is particularly bad comes from
the aerodynamics of SLD’s bigger droplets, which causes them to not only stick
to a wing and tail’s ice-protected leading edges, but also farther back on the
surface, aft of those areas protected by the deice and/or anti-ice systems. This
clear ice is bumpy and lousy for our flying surfaces, and then matters get worse
when the protected leading edge sheds or melts its ice, forming a ridge behind it,
that changes the wing airflow, which effects flight control function. It causes the
ailerons to “snatch” into a full deflection of input, with commensurate aircraft
response. Because this occurs at higher angles of attack, hence closer to stall, the
airplane effectively enters an extreme, aerobatic-like roll maneuver, and is headed
down! Only alert and very capable stick, rudder, and instrument flying skills,
which includes pushing the nose down—as long as the airplane is still upright—to
reduce the angle of attack, and having the altitude to do all this, may save the
situation.
Also, it is worth realizing that the criterion that certifies aircraft for FIKI does
not consider droplet sizes bigger than about 50 microns. Consequently, even
aircraft certified for FIKI conditions are not ultimately designed to deal with SLD.
New rules for icing certification in SLD are on the drawing board, but they will
not affect the aircraft we are currently flying.
Knowing about SLD is a very important piece of the icing puzzle. Realizing
this data did not come along until decades after 1940s icing research, it is worth
noting that common sense developed from experience, taught the pioneers of this
business to stay out of freezing rain, and if we get into it, get out immediately. The
real help of knowing about SLD is what it looks like, so we can get a jump on it.
SLD indicators include clear icing significantly aft of a wing leading edge;
formation all over a propeller spinner, not just the tip; ridging ice on the
windshield and along the cockpit’s side windows. We also need to know ways of
dealing with SLD operationally, such as flight characteristics and how to fly them,
in case we can’t get out of the weather fast enough. Again, we refer to NASA’s
excellent media on these issues.
A point to consider is that despite new advances in icing forecasts, which
include SLD reference, there is still a primary need for the pilot to determine how
much ice is up there and to have enough weather knowledge to sense where it will
be. We’ll find that if things are turbulent, there will be moderate to heavy ice (big
droplets). The same is true for weather that’s intensified by upslope conditions
and, of course, flight through fronts will have heavier ice, as will thick stratocu
clouds in the lee of lakes. Simply being a good student of the current weather
conditions—whether or not it’s turbulent, orographic, or frontal—is the way we
decide how tough the ice will be and, of course, the forecast’s prognostication.
The task is to take our own look and superimpose that judgment on the forecast,
assessing what will be up there waiting for us, and how it may change our flight’s
route and progress.
Dealing with Ice
A trace or light ice would be found in a thin stratus cloud in very cold air that
doesn’t have much moisture. Light ice can, of course, become moderate if we sit
in it long enough. We can continue our flight in light ice, assuming we have FIKI
equipment, but not unless there is a quick way to get out should it become
moderate by forming faster. There should be ceiling below so we can duck under
the clouds, or a known and easy to reach top, or a better weather area behind us.
The speed with which ice forms is the thing that counts, because it affects
what we’re going to do about getting out of it. If it’s light, we can move slower,
talk it over with ATC, and have time to work. If it’s severe, however, we might be
in an awful hurry, and just tell ATC what we are doing and that it’s an emergency.
Before we go any further, let’s talk about deice and anti-ice systems. First,
what’s the difference between them? Well, anti-ice prevents ice from forming and
should be on before entering the conditions. Deice takes away ice that has already
formed. Now, what do we deice and anti-ice? Key items include pitot heads and
other instrumentation probes, static ports, some antennas, and for engines the
carburetor, or in the case of a jet engine, the engine inlet cowl, guide vanes, and
other appropriate areas. This is obviously important, because if the engine doesn’t
run, we don’t fly. We need protection on the leading edges of our wings and tail,
as well as some antennas, and the all-important propellers. Everything that heats
or dribbles fluid along leading edges is considered anti-ice and should be
functioning before we get into the conditions, or immediately upon noticing ice.
Deicers are mostly rubber or similar “boots” along the wing leading edge that
inflate and deflate by pneumatic operation; we operate these after the ice starts
accumulating. We’re going to talk more about these things as we go on, but let’s
start with an important look at keeping our engines running.
Carburetor heat can be tricky. First, one should have a carburetor air
temperature gauge, and then know exactly where the temperature bulb is located
in the carburetor system. The reason is this: If the bulb is located in the coldest
part of the carburetor, one only needs to pull on heat until the temperature gauge
reads something over freezing, like 35 degrees F. If the bulb is located in the
scoop, it may be necessary to carry as much as 85 degrees F indicated, to be
certain that the coldest part, farther downstream, is above freezing. There is about
a 30 to 40 degree F temperature drop from the air scoop to the coldest part of the
carburetor.
This can lead to trouble if there is not sufficient heat. A pilot might be flying
in a condition of cold, dry snow, for example. Generally, this condition doesn’t
cause carburetor ice, because the cold ice crystals zip right through the engine and
don’t get up to a slushy, freezing stage. But if, in this very cold air, a person puts
on heat as a precaution until a temperature bulb in the air scoop reads just above
freezing, the temperature would rise just enough so that the ice crystals would
begin to melt and then refreeze in the colder part of the carburetor system, causing
ice and trouble. I (RNB) learned about this by having a serious double-engine
power loss in a DC-2. Fortunately, there was enough altitude to get the engines
going again, by leaning and backfiring them to break the ice loose.
It’s therefore important to learn where the carburetor temperature bulb is
located and how much temperature drop there is through your system. Then we
can use carburetor heat accordingly, always having it above freezing in the coldest
part of the carburetor, if conditions require heat.
Under most conditions, it’s obvious that heat is needed. It’s used, for instance,
during wet snow, in rain, in cloud with a near-freezing temperature, even in clear
air with high moisture content, if the carburetor is a sensitive one.
A sunny summer day may produce carburetor ice, because warm air can hold
a lot of moisture. So, if it’s warm and humid, carburetor ice is a real possibility,
especially at low power, such as when idling during the glide on an approach to
landing.
Sometimes it is difficult to know whether heat is needed or not. A close watch
on engine performance will tell.
If the airplane has a fixed pitch propeller, watch the RPM carefully to see if
it’s decreasing. When doing this, a pilot has to know the RPM previously set and
also be certain the airplane isn’t climbing. This is because even a small climb
angle will decrease the RPM.
If we get an RPM drop, it’s a good indication of ice. Put on carburetor heat,
and all of it; if we delay and the engine quits, we’ll not have any heat to do the
job. The RPM will drop further, because the mixture has been upset with the
addition of heat. Leave the heat on for a minute and then take it all off. The RPM
will bounce back to its original value if the ice has melted. This shows, of course,
that ice was the problem.
Naturally, we don’t want to operate with this off–on procedure. Now, knowing
there is ice, we pull on enough heat to get our carburetor temperature above
freezing in the coldest part of the carburetor. When we do this, the RPM will drop,
because the mixture has become rich. The hot air we are now using is less dense,
so there’s effectively less air in the mixture. We lean the engine with the mixture
control, and when we do so, most of the RPM loss should come back.
If we haven’t a carburetor air temperature indicator, then we put on heat by
guesswork, lean out, and keep a close eye on the RPM. If it holds, we’ve got
enough heat. If another drop occurs, we should pull on full heat to clean out the
ice, and then apply heat again, except this time a little more.
We don’t want too much heat; we ought to try and use only just enough.
Generally, if too much heat is used, leaning the mixture will not bring back the
original RPM. If excessive heat is used, the engine may run rough and lose power.
If our propeller is the constant-speed type, we’ll never notice any RPM
change, because as the engine loses power, the propeller pitch changes—gets
flatter—and keeps the same RPM. The way we tell, then, is by watching the
manifold pressure gauge for a drop. That will tell us there is ice. Then we go
through the same procedure as mentioned before, except that we use the manifold
pressure gauge, instead of the tachometer, to judge power loss or gain.
If we change altitude, we’ll have to reset the heat–mixture relationship once
leveled off at the new altitude. Most engines use rich mixture for climb, too. With
high-powered outputs, as at takeoff, carburetor heat isn’t needed. If one used it on
takeoff, there would be a big power loss, and even a chance of engine damage. So
we clean out the ice before takeoff, take off without heat, and once in the air
watch closely for any signs of engine icing.
During climb, most engines do not use heat, but under severe conditions it
might be needed. Any deviation from normal climb performance, on instruments,
is a hint of carburetor ice.
We hear a lot about non-icing carburetors and fuel injection systems being
non-icing. These systems don’t have a venturi, like a carburetor does, with its
temperature reducing action, so they don’t ice very easily. However, icing can
nevertheless occur in them, because it is still necessary to bring air in from the
outside for the engine to breathe. If this air has the proper moisture content and
temperature, there is still the chance freezing may occur somewhere in the
induction system, even if it is very rare. However, fuel injection depends on air
entering from an intake that can get plugged in serious icing conditions; this is
known as impact icing. If this occurs, a pressure difference causes an alternate air
source to open—or it must be opened manually—which, although it reduces
engine performance, nevertheless keeps it going.
Clever duct design has reduced this hazard to a minimum, but icing can and
does occur. A pilot still has to keep the possibility in mind. Because
advertisements say “nonicing,” we should not go along innocently believing it as
100 percent true.
In the awful condition where there isn’t enough heat to clear out the ice, a
desperate trick might help. The trick is to try to make the engine backfire in the
hope that the backfire will clear out the ice. Generally this can be done by leaning
the mixture until the engine runs rough and backfires. If it’s successful, the engine
will come back in with a great roar as you enrich the mixture again. I’ve done it
twice under desperate conditions, once, as mentioned, in a DC-2 and the other
time while flying a little Culver Cadet in wet snow. Both times it worked.
Jet engines are a much simpler matter. There isn’t any carburetor, and so there
isn’t any carburetor ice. However, the air inlets, cowling, and guide vanes can
collect ice just as a wing does, and sometimes even when the wing doesn’t,
because there is a temperature drop in that big, venturi-like cowling that can
occasionally cause ice. It can even cause icing issues in clear air, if the air is very
moist, and the temperature just right.
Ice affects jet engines seriously, as the inlet airflow is disturbed and cut down.
Fortunately, the engines are equipped with hot-air passages within the cowls,
guide vanes, and so on. The pilot simply flips a switch, and hot air from the
engine is routed through the passages to keep them warm. The only effect on
operation may be a slight power reduction from air loss in the engine.
Jet inlets may form ice on the ground during a long ground hold waiting for
takeoff during high-moisture with low, but not necessarily below-freezing,
temperature conditions. The jet inlet causes an air temperature drop, and ice may
form on its walls and other areas in the above conditions. The airflow into a
turbine engine is very critical; a relatively small amount of ice can disrupt it to the
point that when we’re finally cleared for takeoff and advance the throttles, we
may get irregular engine action or a compressor stall.
So, while holding on the ground, it’s wise to use cowl heat periodically to
prevent ice accumulation if the temperature–moisture setup is conducive to ice
formation. There doesn’t have to be visible moisture, such as rain or snow, but
simply high humidity; cold fog and wet airport surfaces would be suspect, too.
Individual aircraft operating manuals address this with anti-ice usage criteria.
There is also a problem with ice crystals and jet engines, usually at the tops of
convective activity. In the past, it had been felt there is little if any aircraft icing
potential while flying in cloud at temperatures of -(minus) 40 degrees C or below.
However, investigation of recent events having power loss at these altitudes
indicates enough moisture can be lifted by convective activity, such as
thunderstorm tops, causing icing issues. Ice forms at the back of jet engine
compressor sections where there is not any anti-ice capability, causing engine
surging or even complete power loss. There is also some indication this has an
effect on pitot tube icing. The obvious solution for now is avoiding these
thunderstorm tops, have our anti-ice on, and abiding by the respective procedures
for the aircraft we’re flying, including restarting the engines or loss of pitot
systems. Although we talk of radar and avoiding thunderstorms, there are times
we’re surrounded in a confused combination of cirrus and storm blow-off, with
nothing reflecting for radar. What does help, as mentioned in the thunderstorm
chapter, is tilting airborne radar way down, looking for rain down low in the
storm, below the freezing level. And yes, it can rain way up high, above that
freezing level. This obviously does not affect general aviation operations, more at
home in lower altitudes, but does include corporate jets.
The main point is to be certain that heat is used whenever there is a possibility
of icing. All engines, piston or jet, get their deicing power from heat generated by
the engine, so it’s obvious that if the engine isn’t running, there isn’t any heat.
Don’t let it lose power.
We now have pitot heat on to keep the necessary instruments working, and
engine heat. Next in importance is the propeller. Jets don’t have this problem, of
course, and that’s a very nice part of the jet world.
The Propeller Is Important
Propellers get ice, and when they do, their efficiency drops quickly and then the
engine we’ve kept running is just slinging an icy club, beating up the air but not
doing much pulling. Ice can also unbalance a propeller, creating enough vibration
to shake your teeth.
There are two ways to clear propellers of ice. One sprays fluid on the leading
edge of the propeller to melt ice, and the other method anti-ices the blades by
applying heat to the leading edges.
Without either of these systems, there are silicon-based chemicals available
that can be spread on the leading edges of a propeller to help keep ice off. This is
a stopgap method and not what we should depend upon over the option of a
mature propeller deice/anti-ice system. These same products, when rubbed into
the surface of the wing deicer boots, make the ice come off more easily, because
pieces of ice don’t tend to stick to the boot. The preparation doesn’t have a very
long life and is washed away when the aircraft flies through rain, necessitating
renewed application.
There are two ways to use deicing equipment. One is deicing, and the other is
anti-icing. In the first case, one waits until ice has formed and then turns on the
fluid or heat to get rid of the ice. Unfortunately, the ice never comes off evenly,
and when it comes off one propeller blade and not the other, the unbalance makes
a terrific vibration. Also, on a multiengine airplane, the ice slinging off often hits
the fuselage with a loud whack that’s disturbing to one’s nerves. It doesn’t hurt the
airplane particularly, but any old DC-3 will show dents on the side of the fuselage
next to the propellers, where hunks of ice have beaten on it through the years.
More currently, we see abrasive plates over the fuselage skin, their paint often the
worse for wear. Sometimes, however, the prop ice sticks well and will not totally
clean off.
The better method is to use the equipment as anti-ice. This simply means to
get fluid or heat on before entering icing conditions so as to keep the ice from ever
forming.
If there is ice on a propeller, and the deicing method used is having trouble
getting it off, try running the RPM up and down in surges to give extra, and
irregular, centrifugal force to help sling the stuff off.
Propeller ice will often form before visible wing ice, and if one is flying in
cloud and an airspeed loss occurs without wing ice, it may be because of propeller
ice. I saw this when doing research work with a B-17. We had a stroboscope to
look through. It “stopped” the propeller visually while it was spinning at its
normal RPM, and you could look at the prop as though it were standing still. A B17 was convenient for this, because you could see the props closely from the
navigator’s station in the nose. It was amazing to me to see ice on the leading
edge of the blades when we didn’t have a bit anywhere else on the airplane. And
this happened quite often.
So don’t be bashful about getting the propeller anti-icing gear into action well
in advance or under any suspicious condition. The propellers are most important,
and in decades past, with less-efficient and functional boots, if one could have
either wing deicers or clean propellers, the choice would be propellers. If they
were doing their work efficiently, we could pull a lot of those old thick-winged,
lower wing-loaded, ice-covered airplanes around the sky—most of the time.
However, today, we’ve learned this should be considered a last-ditch situation,
and it’s better not to get ourselves into these predicaments in the first place. We
should have an approved ice protection system before even considering we’ll
seriously fly ice.
Wing Deicers and Anti-Ice
As mentioned earlier, we have three kinds of devices for removing ice from wing
and tail leading edges: pulsating boots, weeping fluid, and hot wings. The boots
are always deicers, while hot wings and weeping fluid are considered for antiicing and are most efficient when activated before entering icing conditions.
Boots
Years back, there was question of how much help deicer boots really offered.
Thousands of hours of weather flying was done without boots being very
effective.
A good example of this occurred in the B-17, in which I (RNB) did a lot of
research flying. The boots, during those difficult times of WW II, were made of
something less than the best rubber and we continually had problems with them
developing tears. Each time we had to replace the boots, it was a long
maintenance job. Finally, we had a bad tear and couldn’t find replacements. We
had the crew chief take them all off and finished 18 months of weather research
flying, a lot of it in ice, without boots on the airplane. I was particularly fussy,
however, about keeping the propellers clear of ice and the engines running.
An aspect worth considering is that the research B-17 was much lighter than
one prepared for a real bombing mission, so it had a more favorable power-toweight ratio. Having power to pull through ice is a big help, although this is not a
conclusive concept, and certainly nothing on which we can pin accurate criteria of
operation. Consequently, it’s not a reason to stay in icing conditions.
Despite boots being far better these days, unless we are in light or a trace ice,
they or any other ice protection should not be considered as a means to fly
continuously in ice. At the risk of boring the reader, we repeat that the worst ice
offenders on the airplane are the antennas, landing gears, probes, and places where
we cannot place ice protection, let alone heated fuel vents so the engine keeps
running.
A concern was to have the ice break off clean, instead of having a leading
edge with ragged pieces of ice sticking out. This can be worse than a smooth
coating of ice. In years past, we’ve seen cases where the airplane had a smooth
coating of ice when the boots were turned on. Then the ice broke up in chunks,
with pieces left on the airplane, even big hunks that stuck on the leading edge and
went up and down with the boot, but never blew away. Sometimes the airspeed
fell off 10 knots after the boots were turned on and the ice cracked. This leads into
techniques for operating today’s boots.
In the past, it was felt ice should be allowed to build up to ¼ inch to ½ inch
before the boots were actuated. It was felt that as the boots pulsated up and down,
a thicker accumulation theoretically broke off in a manner that allowed the
airflow to blow it off and away. Then when the boots did their job, it was time to
turn them off and wait until another coating of ice formed, repeating the process.
Today’s boots seem to be effective even as the ice begins to form, which is why
many manufacturers recommend turning the boots on at the first signs of ice.
Many systems have automatic off–on scheduling, which not only seems to do a
good job, especially if related to an icing sensor, but also keeps us from forgetting
them if things get busy. These systems seem pretty clean, and any hunks of ice
tend to blow off from continued actuation. One other concern is that if an aircraft
is near a critical angle of attack for its contaminated wing, that ¼ inch, give or
take, of ice, could be the critical amount needed for stalling the ice-altered wing.
This is, of course, variable due to many factors, including power-to-weight ratio,
type of aircraft, and how we’re flying it. In other words, unpredictable. Also, an
aircraft’s stall warning works in relation to a clean wing—one without ice—so
possibly, it will not warn us before stall when in an icing situation.
An airplane that flew through a lot of ice! The black deicer boot worked hard, but
still had pieces of ice stuck to it. The ice on the wing’s bottom is thick, and a ridge
of ice sits aft of the deicer boot. All of this is an aerodynamic nightmare. The ice
as seen indicated SLD-type icing or maybe an aircraft struggling along at a high
angle of attack or maybe both. Even with approved FIKI equipment, this was a
dangerous situation. We should not consider this picture as a reason to fly in icing
conditions. (PHOTO COURTESY OF PURDUE UNIVERSITY)
Today, deicer boots are bonded to the aircraft making a cleaner, more
aerodynamic fit, as compared to days past of screwed metal strips holding them in
place. Also, better designs of inflation tube have seemingly made deicer boots a
much better benefit for today’s aircraft. It’s also worth mentioning no aircraft has
been approved for FIKI (known icing conditions) without some form of wing
anti-ice or deice; the latter being boots. Overall, the recommended procedure for
operating deicer boots is to consult the aircraft flight manual, then do what it says.
Hot Wings
Hot wings are something different, as the leading edges are heated, usually from
jet engine bleed air, although some are electrically heated through boots
containing heating elements. They are best used as anti-icing. In other words, they
are turned on and the wing is heated before getting ice, so the hot leading edge
never lets ice form.
When used as deicers—that is, turning them on after ice has formed—they
either melt the ice, or break the bond which lets the ice blow off. Sometimes,
when the ice melts, the water can run back on the wing and refreeze, forming a
spoiler-like ridge on the top of the wing. In theory, a ridge forming behind the
heated leading edge may affect airplane performance, or roll-control issues. This
varies with each aircraft’s design, and ultimately tests approving certification are
reflected as operating procedures prescribed from that aircraft’s flight manual.
Overall, on jets, melted-ice ridge issues seem rare, if at all. Also, a hot wing, when
using bleed air for its hot air source, is dependent on a certain level of heat.
Consequently, a bleed air–dependent system often requires a minimum engine
power level during its use for anti-icing; bleed air temperature increases as a
function of increased power.
Another reason hot wings are best used for anti-icing is that with this adequate
heat, the ice is not just melted, but vaporized; hence no water to run back on the
wing. However, if we turn on heat after an accumulation of ice, as the heat process
reaches normal temperatures, there is a brief period where it passes through the
melt-only temperature, creating water, before enough heat for vaporization is
produced. This water could run back on the wing, and may leave a small ridge, but
a good hot wing works well and quickly, so “ridging” is usually a minimal issue.
Again, following the aircraft’s certified procedure of anti-ice use is the way to go.
Fluid Anti-Icing
This system pumps a glycol–based antifreeze solution through panels having
many tiny, precisely drilled holes. These panels are mounted on the aircraft’s flight
surface leading edges. It also is distributed on the propeller and windshield,
similar to when alcohol was used for this same means as far back as the 1930s.
The fluid forms a protective film over flight surfaces, which according to
manufacturer data chemically breaks down the bond of ice to the airframe, where
airflow and aerodynamics remove the ice.
The system can be used as either an anti-ice or deice system, depending, of
course, on whether it is turned on before ice formation or after. The fluid’s flow
over the wings and tail has the benefit of coating the surface aft of the leading
edge dispersal, which in theory assists in preventing run-back ridges, as well as
potentially helping prevent SLD icing on wing surfaces; however, we caution that
this is not considered a viable reason to fly in SLD icing conditions. As a matter
of fact, the manufacturer data states their system, like any good deice/anti-ice
system, buys us time as we seek nonicing conditions.
The system has a successful operational lineage since the 1960s, as the
approved system for the DH-125 business jet. Many say it worked very well.
Known as TKS, this system is available today on quite a few new aircraft,
including single-engine piston airplanes, as well as being retrofitted to many older
designs. There are FIKI-approved aircraft that have TKS and some that do not, so
if one seeks such a system, one must research this through the aircraft flight
manual and other paperwork. The only limitation seem to be fluid capacity, but
most airplanes seem to hold about two to three hours’ worth at continuous
operation; like fuel, this just requires attention and common sense.
And what does TKS mean? It is the initials of three partners who came up with
it in the early 1940s. Tecalemit was a pumps and valve expert, Kilfrost came up
with the fluid (and we see their products today squirting over aircraft in hideous,
frozen weather), and Sheepridge Stokes figured the aerodynamic magic.
Considering this system is well appreciated by many users today, one again asks
what really is new in the flying business.
We Have to See
An important item that needs deicing, or anti-icing, is the windshield. If we make
a low approach through icing conditions and get the windshield covered with ice,
we cannot see to land.
The ways to solve this are:
1. Hot windshield, either through the whole thing like jets and turboprops or a
dedicated heated unit mounted over the windshield, in front of the pilot.
2. Alcohol or TKS fluid to squirt over the windshield.
3. A window one can open to see out.
Historically, we have handled the windshield ice problem in the reverse order.
Back in DC-2 and early DC-3 days we (RNB) all carried a putty knife in our flight
kit. It was used when ice covered the windshield. We’d open the side window,
reach out into the icy blast around to the windshield, and scrape off enough ice to
give a small clear area to peek through while landing.
Then we got alcohol. This would squirt across the windshield and as it melted
the ice, the windshield wiper would carry the ice away or knock it off. It was
smeary and partially effective. We still carried putty knives.
An occasional heavy coating of ice wouldn’t yield to either putty knife or
alcohol, and there were cases where the pilot bashed out the windshield with a
fire extinguisher to have a place to look out!
Now we have heated windshields that seem to do the job well. All the trying
days of fire extinguishers, putty knives, and alcohol are taken care of by flipping a
switch.
Windshield ice! It’s an older picture, but ice does the same, new or old airplane.
This aircraft had fluid deicing (alcohol), which we see only made a futile dent in
the issue on the left lower side and under the eventually stuck windshield wiper.
Landing would be a big issue! You might see enough out the curved front of the
side window, or maybe not.
However one does it, keeping the windshield clear is a very important part of
ice flying. If the methods available are marginally adequate, then a window that
can be opened for viewing is a must! Flying any airplane that does not have a
window that can open, or at least enough of a look to land, is something to
ponder. On a single-engine aircraft, a covering of oil from a bad leak can make a
windshield no more transparent than a solid wall, let alone a coating of ice. Some
general aviation aircraft, as we know, have generous side windows that open, like
high-wing Cessna’s. But when we’re down to those small side windows that open,
which are located in the main side window, windshield icing, and for that matter
previously mentioned heavy rain, is an issue to contemplate.
In kind of an interesting story of habit patterns, the 747s, which your first
author flew when they were new, didn’t have a window that opened; it was
possibly the first transport ever certified that way. The old timers who first flew it
—most who learned to fly in biplanes and started airline flying in DC-2s—got
itchy about no window to open, but soon realized such was not a problem, due to
excellent heated windshields and good wipers. Most other Boeings do have
windows that opened, and although there we’re never issues of seeing out the
windshield, it was helpful for quite a few things, including views of the wing,
engines, and airport surface in lots of lousy winter weather. You could also run
your hand over the outside of the fuselage to see what the precipitation was doing.
The only personal window complaint was in the 727; on the ground, and
obviously not pressurized, a good deicing would leak around the frame, dribble
on us, the flight kit, wrinkle some charts, and drip into your coffee, making it taste
weird.
In summary, we’ve taken a look at the protective devices against ice. They
don’t cover the entire airplane. Even if propellers and wings are kept clean, ice
will build up in other places, causing drag that eventually will be very serious,
which gets us back to the original statement that the first rule of flying ice is: do
something to get out of it as soon as it occurs .
How We Fly Ice
Ice flying begins before we ever leave the ground. A number of things need
checking. First and most important, is there any frost or ice coating on the wings?
If so, we have to get it off before takeoff. The rough surface of the ice or frost can
ruin the airflow over the wing, so that the takeoff run is very long and liftoff likely
to be impossible. A Bonanza tried to take off here in Vermont on a lovely fall
morning. There was a slight coating of frost, thin enough so the pilot evidently
thought it would not affect the aircraft’s performance; he elected to go. The
airplane never got off, piling up at the end of the runway and burned—three
people dead. Probably everyone is aware of high-profile accidents because of frost
or sticking precipitation on wings. It’s a no-win situation and so unnecessarily
sad, because when we’re safe on the ground, we have complete control and can
get the stuff off before trying to take off. It isn’t a matter of being in a situation;
it’s a matter of creating one by impatience. Remember, the most innocent-looking
thin coating of frost is dangerous, and flight should not be attempted until it is
removed!
Removing frost, frozen rain, snow, or whatever has dirtied up the wing has
two aspects: one is deicing, and the other is anti-icing. If it’s a nice day, and we
want to remove the contaminates, to use a fancy word, we wash it off with a
glycol–based deicing fluid, very often mixed with water and generally available at
the FBO. This process of removal is deicing.
If, however, it is precipitating, and we are going to take off, then anti-icing is
necessary, because the glycol–water mixture used for cleaning the wing will only
prevent falling precipitation from freezing on the airplane for a limited time. So
now, after clearing our aircraft of frozen contamination, we have another
application of fluid applied to prevent further contamination, which must do so
over the time it takes us for taxing to the runway and taking off.
The kind of fluid we use for this anti-ice process varies with precipitation
type, intensity, and outside temperature, as well as the type of fluid used. There
are currently about four fluid grades, often known as Type I through IV, offering
different viscosity and subsequent “hold-over” times, again depending on
precipitation type, intensity, and outside temperature. The hold-over time is how
long we can sit there in whatever type of frozen precipitation, having it absorbed
and melted by the fluid, with the flight surfaces supposedly clean for takeoff.
When we takeoff, we want these fluids to shear off the flying surfaces before our
takeoff speed. Some of the thicker fluids require higher jet rotation speeds, so
slower aircraft will be using thinner fluids; it’s something to look into before
operating in these conditions.
Depending on the fluid type, dilution (realizing some fluids must be diluted,
some can go either way, and some can only go full strength) and all the other
factors mentioned, these fluids handle almost all freezing precipitation as well as
rain on cold soaked wings, except freezing rain; that’s a no-go item. Frankly,
taking off with freezing drizzle or light freezing rain isn’t such a fuzzy and warm
feeling, but then again, we evaluate if we’re a light single or big jet.
So if the taxi is long, and takeoff delays are in progress, you may be on the
ground for considerable time with “stuff” falling and collecting on the wing.
Depending on the extent of one’s evaluation procedure, it can become complex,
with iffy factors still prevailing.
On determining your precipitation type and temperature, intensity comes into
play. That may cross-reference reported visibility. Then we look at the type of
fluid used, not just in number but manufacturer. Is it diluted or not? Finally we
look at guidelines, which can be a whole section in our operating manual. It is
there that we find out how long we can theoretically wait in the same type of
precipitation, and still have a clean wing. For example, a generic Type II table,
using the stuff at 100 percent, shows that on a −2 degrees C day with light to
moderate snow we can sit in a range of 40 minutes to an hour. If somehow light
rain is mixed with light snow, we must revert to the light freezing rain table,
which now says we are good for just 40 minutes. However, if it was applied as a
50/50 mixture of water and fluid, that 40 minutes slips to 8 minutes. All these
numbers mean the same or less precipitation, temperatures staying in range of the
criteria, and so on. If an aircraft in front of you is blasting snow all over your
airplane, or the wind increases, doing the same thing, the fluid may be sheared off
before we start our takeoff roll, let alone the blowing snow coating our airplane.
Then comes the moment of truth; we’re ready for takeoff and wonder where
we are in that time range of 40 minutes to an hour. If it’s longer than that time
envelope, we usually return to the ramp and have it checked; reapplying fluid and
starting the process all over again.
So, the responsibility is dumped on the pilot, realistic or not, to be certain the
wing, tail, and engine inlets, are clean before taking off. How are we sure of this?
Taking a look at the wing, under strong light if at night, can give a false
impression, because the ice might be clear and the wing may look free of it, when
it really is not. Using a flashlight through a cabin window is almost useless, as the
light glares back in your face. The only sure way is an inspection from the
outside, which is tough to do at a busy airport just before takeoff. Imagine
climbing out to do that at runway’s end, airplanes waiting behind you, wind
blowing, wet snow falling, and you commence a methodical walk around
inspection. Kind of unrealistic, but it is your responsibility, so if you are uncertain,
then the only thing to do is taxi back, inspect the airplane from outside, and deice
it again if necessary. Unfortunately there’s no pat procedure or method, and, as
said, it’s the pilot’s responsibility. As the FARs say in Part 91.3(a), “The pilot in
command is directly responsible for, and is the final authority as to, the operation
of that aircraft.” And that goes, be it a Piper Cub or a Boeing 747.
An important point we feel worth emphasizing: don’t think you can blow
snow off the wing! If it’s super dry and just resting there, perhaps you can, but if it
sticks at all, or there’s something sticking under the dry snow, we’ll never blow it
off. This idea is an invitation for trouble. Try it on a car someday; even going like
crazy down the highway not everything comes off, which is about the takeoff
speed of a single engine airplane. Another issue is when we brush snow off an
airplane and think it’s clear, but under the snow was frozen contamination stuck to
the wing. If we don’t run our hand over the surface we’ll never know, so we need
to inspect the wing carefully, running our hand over it, getting a ladder if we need
to, seeing what’s under the dry snow. So, if it’s only dry snow, get a broom and
sweep it off!
If, for some dumb reason, we try to take off with frost on the wing, or other
frozen precipitation, we may become airborne, but will probably be unable to
climb out of ground effect. The airplane will become very unstable laterally, and
it will want to roll side to side, as though falling off on a wing at stall, because
that’s what is happening. Fly as best you can, you might fly out of it, but chances
are you’ll never get out of ground effect, which is about half the wingspan high.
Most times, the airplane will not even get that high, but will just charge off the
runway’s end into whatever awaits. This is all very dangerous business.
Is Your Airplane Equipped to Fly Ice?
One may ask questions such as, “How much ice can a Cessna 172 carry?” How
much an airplane can or cannot carry isn’t the question. The real question is,
“Does FAA say the airplane can be flown in ice?” If it isn’t FIKI-approved, then
we don’t have any business flying it in ice. Just because an airplane has deicer
boots and heated propellers, that does not mean it’s FIKI approved; we dig into
the paperwork and find out. The FAA approval for an aircraft to fly ice isn’t
simply a test of how much ice it can stagger around with, but it is an examination
of the entire aircraft and its systems. Do the fuel vents stay open, do controls ice
up, do air intakes become clogged with ice, can the windshield be deiced? A host
of questions, and if our airplane isn’t FIKI-approved, we may not simply get in
trouble because of the ice on the wing. What if the controls ice and cannot be
moved, or a fuel vent clogs with ice? Think about all those things and realize if the
airplane isn’t ice-approved, one hasn’t any business flying ice in it. A lot of things
could happen.
Propellers, Jet Inlets, and Other Fixtures
As previous mentioned but never too many times, the propellers should be clean.
On damp, misty, coldish days, it’s wise to use anti-icing on the propellers right
from the start of takeoff. There is some evidence that one can get propeller ice in
clear, but very humid, cold air.
Under similar conditions, a jet engine inlet may ice, and so engine heat may
not only be wise, but is most likely required as standard procedure. The criterion
for this usually includes temperatures that are above freezing, because, as also
mentioned earlier, air expansion at the engine inlets causes a cooling process; kind
of like the carburetor routine. Depending on the engine and aircraft, anti-ice is
usually required between +6 to +10 degrees C or less, and when visible moisture
is present. That definition includes individual or combination amounts of rain,
snow, frozen anything, wet airport surfaces, and fog; this latter criteria is based on
airport visibility of a mile or less. Obviously, we consult the aircraft flight manual
for the definitive word, but if stuck with nothing, these are some things to think
about.
Back to our bad weather checks, the airplane’s controls should not have any
ice obstructing their movement, and the landing gear should be clean, especially if
it’s retractable. Check the pitot head and static sources closely to be certain they
are not blocked by ice or frozen slush thrown up by the wheels during a previous
landing or by precipitation that stuck on the airplane while it was standing.
If it’s very cold, be certain there has been heat applied to warm the
instruments. A cold gyro may be slow in coming to speed, and its action will
consequently be sluggish, which would be bad if one took off and went on
instruments quickly. The windshield may fog up during takeoff, and we’d best be
prepared to defog it with whatever means are available. After an engine is started
it’s important to warm it up thoroughly, so that when we take off, it will put out its
normal power and continue to do so at its maximum power.
Ice Flying Starts on the Ground
Taxiing can be quite an interesting experience on icy, frozen, and snowy surfaces.
First, if there’s snow and it has been plowed, it is important to be certain that
when turning, wingtips, and the tail will clear the snow banks, especially if we are
in a low-wing airplane.
The runway surface may be ice-covered and slippery, so a combination of
slick surface and strong wind trying to weathercock the airplane makes taxiing an
adventure.
First, taxi slowly, really pussyfooting along. The most important point is to
use the brakes carefully. Use them in little bursts, but don’t lock the brakes. If we
do, as soon as they lock, the wheel stops and slides, ice-skate fashion, over the
surface. Tapping the brake on and off at short intervals will give braking for an
instant, each time the brake goes on and then is released just before the wheel
would stop and become a sliding ice skate.
I (RNB) operated my B-17 in the Aleutian Islands of Alaska. The weather
there often causes sheet ice to cover the runways and taxiways. The winds blow
hard, the taxiways are narrow, and a B-17 with its big fin wants to swing around
like a weather vane. I had excellent luck getting around by using the quick onand-off braking method.
Although weather cocking is usually thought of as a problem for aircraft with
conventional (tail-wheeled) landing gears, we can feel the tendency in any
aircraft. Even larger airliners get a noticeable shove in a healthy crosswind and if
we’re taxiing on a slippery taxiway, there can be issues. It’s a goosey feeling
when a gusty wind keeps trying to shove a big airliner sideways, while each stop
gives a little slide and tiny weathercock; especially someplace where we taxi right
next to a body of water or an embankment.
Sometimes, on slick taxiways, it’s impossible to get the brakes to hold while
running up the engine, so one might have to run them up while sliding. This takes
thought and planning and careful observation of where one’s sliding.
The start of takeoff can be swishy as a crosswind tries to slide the airplane
around before there’s enough airspeed to make the rudder effective for steering. It
takes care, and the winter isn’t any time to do things in a rush–rush fashion. This
is an other example of where the modern world still needs good old-fashioned
stick-and-rudder skill. We need to roll our ailerons into that upwind wing and
work the rudder in small but timely corrections, just like one should do when
flying a tail-wheeled aircraft.
Turning onto a slick runway at high speed for a running takeoff is a very poor
practice. The nose wheel will not have any traction, only skidding as we use it to
straighten out the airplane and aim down the runway. The nose wheel may turn,
but the airplane will not, and everything will slide sideways out of control, headed
for the boundary lights.
Where We Find Ice
Let’s look at the places we find ice and how to get out of them. As always, we are
back to our first look at the general weather picture. With today’s icing forecasts,
especially the graphical ones, we can get a good look of expected ice along our
route, both from overhead and a profile view. However, it is still important to see
where the fronts are, because we find the most ice in the fronts and lows, and
being the most difficult ice, it’s what we want to avoid. Ice can be found in large
amounts out of fronts, too, but it’s easy to avoid if a pilot understands the weather
picture. Again, forecasts are aids to the more important understanding of the
weather’s big picture. Should we pick up on the weather systems moving, say, at
different speed or magnitude, we’ll have an idea where changes to the icing may
be, because we understand the original synoptic makeup. Ignorance can find a
pilot desperately in trouble when it isn’t necessary.
The classic case of this is the Allegheny Mountains after a low and its
associated fronts have gone off the East Coast, out to sea. Although the fronts
have gone, we find the country from Harrisburg, Pennsylvania, to Columbus,
Ohio, cloud-covered. The mountain weather-reporting stations are grim: low
ceilings, snow falling, and visibility nil. A pilot flying low, trying to stay VFR,
would have a desperate time. It would be impossible to cross the ridges, as they
would be in cloud. A pilot flying a few thousand feet higher, on instruments,
would find they were getting ice at an alarming rate.
A clever pilot would know that all this was an air-mass condition, with
reachable tops above, and it is possible to be sitting in sunshine on top of a
seemingly endless blanket of white, relaxed and comfortable.
Countrywide, such air-mass stratocumulus decks are common in winter after
fronts pass. The more notorious of these occur not only in the Allegheny
Mountains but in all the area downwind of the Great Lakes, sometimes for
hundreds of miles, the mountainous Northeast, and the Pacific Northwest,
downwind of the ocean. What’s happening is the new cold air is unstable, has
moisture, and builds a cloud deck. On the ground, after a front has passed, we are
often under clear skies. Then cumulus start to build. At first they are pretty, white,
scattered cu, then they become broken and dark, finally turning into a gray
overcast sky that spits snow in blustery cold winds. This is the real cold air mass
moving in.
That cloud layer has ice in it. The only decent place to be is on top. The tops
will vary in height, depending on a number of things.
Tops are higher in mountainous areas or to the lee of large bodies of water,
such as the Great Lakes, where the air picks up moisture. The tops will be higher
when we are closer to the frontal system, though not directly behind it, because
there is often that clear area where the new unstable air hasn’t had enough time to
get in and start its action. This clear area isn’t very wide. It often fools people into
thinking everything is wonderful ahead, that the front has passed, and now it’s
clear. These hopes fade at 100 miles or less along the way, as clouds begin to
form, the bases get lower, and cloud tops get higher.
As we get farther and farther from the weather system, the tops are lower, the
bases higher, and the showers less frequent, until they die out altogether. This
happens because the air has been in the area long enough to be modified, and its
instability is reduced as the air temperature and ground temperature become more
nearly the same.
Temperature Again
This temperature difference between ground and air is the reason why we often
see beautiful, clear, cold, winter nights and, as we look at the sparkling stars,
decide tomorrow will be a lovely day. Tomorrow turns into an overcast, cold, gray
day. Why? Simply because when the sun came up, it warmed the ground; maybe it
didn’t feel warm, but it was warmer than the air, and this started the air rising and
triggered the same process that makes cumulus clouds in summer.
Where Are the Tops—and the Bottom?
If we are going to fly in the area of the heavy deck with its ice and snow, we
should try to learn what the tops are before we take off and start climbing to find
them. Area forecasts give us an idea what they as a general area, and graphical ice
forecasts let us search altitudes where ice begins and ends. We talk with the FSS,
asking for PIREPs or searching for them on computer weather sources. A phone
call to a local approach control or even an ARTCC facility can access aircraft
already up there. And of course, ask around the airport, whether of a pilot who
just landed or an arriving aircraft on the radio, even an airliner. The airline pilot is
happy to help out. Once airborne, we can ask aircraft ahead their conditions or
contact Flight Watch for PIREPs. Most importantly, we shouldn’t keep what we
are experiencing a secret. Call Flight Watch or FSS, and more locally, use the
current ATC frequency to give a PIREP. This is especially important if we are the
first ones out there, maybe early in the day. We tell them what ice we found
during our climb and what we have for the tops.
If we are climbing to top a deck, it’s best to climb quickly—not at a nosehigh, staggering angle so that ice will form back under the wing and hurt, but at
high airspeed, with plenty of power. Stratocu clouds have the most ice near the
tops, especially the SLD type of ice, so don’t struggle along clipping through the
tops; get up and out of the clouds.
Occasionally there are bits of trickery in getting on top. Out of Pittsburgh,
Pennsylvania, headed east, the highest tops and toughest ice are located in the
mountains east of Pittsburgh, over the Laurel and Chestnut Ridges. Taking off and
then climbing toward the east means one climbs through the thickest clouds. To
the west of Pittsburgh, of course, the land is lower. Back in DC-2 and DC-3 days,
we often got a clearance to take off and climb toward the west. The tops would
always be lower that way. Once well on top, we’d turn back east for New York. It
was a way to get up through the minimum amount of cloud. The tops to the west
would often be 7,000 feet, while the tops over the ridges might be 12,000 feet. We
can still use this today, when flying many types of general aviation airplanes.
Flying in winter over the mountains of the far Western United States can be
difficult, with a combination of moist Pacific air being lifted up the mountains of
the coastal ranges, the Cascades and Sierras. It can be a problem, at various times,
from the Canadian border to Mexico. The fact that the airplane must operate at
extreme altitudes because of the high mountains—higher than those of the eastern
states—adds a trying factor. In fact, with certain lower-performance aircraft, it is
an impossible one. While the West Coast is generally blessed with good weather,
when it is bad, it is very bad: be certain to check what the tops are before takeoff.
If planning to fly on top, we don’t experiment and find ourselves still trying to
climb with lots of ice on the aircraft and no tops in sight!
Descending through icy decks should be done quickly without being wild and
panicky about it. Ice raises the landing speed, covers windshields, and makes a
low approach tougher. We don’t want to get any more ice than necessary during
the descent.
ATC will often hold or dawdle you about in the icy deck, and when they do,
it’s time to tell them that you are getting too much ice and you don’t want to sit in
the deck any longer than you have to. They’ll generally help if you let them know
you have a problem, especially if you request an altitude change and are willing
to accept a heading change to give ATC a broader range of options to clear traffic
and get you down.
We need to know where we’ll break out; in other words, where are the cloud
bases? If it’s a long way down, through icing conditions, we may want to request
staying on top as long as possible, then making a “slam-dunk” down through the
mess, on to the approach and landing. Obviously, we don’t want to get so hyped
about the “slam-dunk” that we are late in slowing down and setting up a stabilized
approach. These types of descents can be an issue with piston-engine aircraft,
where we are concerned about carburetor icing during low power and rapid engine
cooling. Also, descent can be helpful PIREP time; both for us and sharing our
conditions for others. A good example is the northwest approach to Burlington,
Vermont. The upslope from Lake Champlain can create a quick but significant
clout of ice as the approach passes over the Green Mountains before starting down
the glideslope. A good PIREP to the tower and approach control can be a big deal
to someone unaware, who may suddenly find a nice chunk of ice buildup just
before landing; especially if they are flying an aircraft that is not approved for
icing conditions. Their option might be letting down away from the mountains on
another approach, where there is usually better ceiling, or maybe even scattered
clouds, and entering the landing pattern for a nice VFR event.
These are times that having really good hand-flying instrument skills are a big
help. Hand-flying may facilitate a quicker approach—hence less time to build ice
—than using an autopilot. One day I (ROB) watched my father shoot a step-down
VOR approach into Montpelier, Vermont, in a Cessna 172, with a stratocumulus
deck hovering over the higher hills of the area. The deck was not too thick, but
nevertheless he wanted to get through it quickly as he suspected some ice, despite
no reports in the area. He’d been retired from the airline for quite a few years, but
had kept his flying sharp. Hoping to find a hole in the clouds from downflow of
the local mountain wave, there wasn’t one—wave or hole. At least it wouldn’t be
too turbulent, a fact my mother would appreciate, as she sat trustingly in the back.
Neither of us were thrilled about getting ice, and considered overflying
Montpelier for Burlington with somewhat better weather. However, after a chat,
we agreed the bases were well above minimums, and the deck not too thick, so he
said: “I’ll fly it like a DC-2 getting a load of ice.” I figured this ought to be
interesting, and down we go. We entered the cloud tops with our speed up, a good
rate of descent, carburetor heat out, window heat full (and fairly useless), quickly
crossing the final approach fix outbound. He pirouetted through a timely
procedure turn, yet with sensible bank angles and precise flying, then made the
“dive and drive” to breaking out of the clouds and a nice landing. We had maybe
⅛ inch of ice, but the disclaimer says that he didn’t fly ice much, if ever again, in
our trusting 172. Overall, despite all his experience, he was a really conservative
aviator. Truth is, years later, in his late 80s, he used to practice this stuff under the
hood in VFR conditions, using just the turn and bank, steep turns and all.
So, all said and done, it’s important, then, to know if cloud decks are air mass
or frontal, and where both the tops and bottoms are lurking.
Fronts and Ice
Knowing the front locations is the most important factor in foreseeing ice, but
there are other hints, too. If a cloud deck exists, and the surface reports show a
good, solid wind of at least 10 knots (not a light, variable wind) from a direction
we normally associate with good weather (like northwest in the East Coast area),
we can feel pretty certain that the clouds are air mass and not frontal.
If we are on top, it should be clear above us, or perhaps we may have only a
very high, thin cirrus deck left over from the system to the east. If, however,
thicker high clouds are overhead, and we are between layers, we’d better check to
be certain that something isn’t stirring in the general weather picture.
The first thing to do is look westward, or in the direction away from the
weather movement. If these high clouds thin and decrease in that direction, with
perhaps blue sky peeking through and a general clearing “feeling,” then the clouds
above us are probably leftovers from the past weather system.
If, however, it looks just as cloudy to the west, we must be suspicious of
another weather system moving in, or the one to the east being stalled, or perhaps
an occlusion bending back.
With this gloomy outlook, it’s time to check surface reports in all directions
and try to get any new or revised forecasts, and if we have the instrumentation,
look at a satellite, surface chart, or radar. Once I (RNB) carried blank maps in my
flight kit and would draw up a crude weather map from weather reports received
in the air. I could quickly see a change in wind circulation and begin to notice a
change in weather patterns. This proved to be useful in a number of ways, like
seeing a trend for deteriorating weather or for better weather, and it was excellent
training to develop a deeper awareness of what weather does. But you know, if we
are still flying an airplane without electronic displays or portable electronics, this
is a perfect example that good habits of the past are still quite valid.
Air-mass clouds may have snow showers, but they don’t have large areas of
steady snow. Steady snow or rain indicates that something more extensive than
air-mass weather is in progress. This we can see from surface-weather reports. An
exception is in mountains with unstable air being lifted. Then the snow might be
steady with very low ceilings on the upwind side, but just snow showers
elsewhere. The steady snow is the result of the wind constantly lifting the air up
the mountain. The same effect can be found in the lee of lakes, especially the
Great Lakes. Even Lake Champlain in Vermont and New York can cause heavy
snow downwind from it and is given a further boost from upslope against the
mountains to the east. This is commonsense stuff we learn from weather study,
and something we won’t get from electronic weather; it will tell us what it’s
doing, but if we know why, we can often spend less time staring at weather
information and more time looking out, making overall go–no go decisions, and
flying the airplane.
An Ice Airplane
When we fly fronts that have ice in them, we need the proper equipment. This
time, the equipment is the airplane itself. It should have the ability to climb at a
good rate to a fairly high level without much trouble, 15,000 feet for example, and
it should have a good enough cruising range to give a wide choice of alternate
airports. If it has a piston engine, it’s likely turbocharged, and whatever the power
source, it’s approved for flying icing conditions.
Not Always in Clouds on Instruments
We have to define something before we can go much further in ice flying. That
something is the difference between being on instruments in a cloud, and being on
instruments but not actually in solid clouds. Sounds a little complicated. Say we
are flying in dense haze or smoke with a lower cloud deck that obscures the earth.
In this condition, we are not really flying in a cloud, but we can’t see anything, so
we’ll have to fly by instruments. Now, take this condition and make the haze
snow, and we have the same thing: We are not really in a cloud, yet we are on
instruments. This occurs very often in winter instrument flying. It’s not a question
of cloud density; it’s just that we are either below a cloud deck or between layers
of clouds in snow or haze. Whenever this occurs, we do not get ice! The only time
we’ll find ice without cloud is in freezing rain or drizzle, whether it’s the sole
precipitation or mixed in with the snow. Otherwise, ice is in an actual cloud,
where we find those supercooled liquid droplets. We can fly at times for hours in
such cloudless instrument conditions and not get any ice, even though it’s below
freezing.
Warm Front
Taking it from the ground up, as if we’re taking off and climbing out of an airport,
the structure of a warm front, and any condition that involves warm air
overrunning colder air, is something like this: At first there probably will be a low
cloud deck, its base at perhaps 500 to 1,000 feet. This deck is caused by the
precipitation falling into the colder air, and its thickness will depend on how long
the precipitation has been falling and how close we are to the frontal surface. It
may be scattered and only 1,000 feet thick, or it may be solid and 8,000 feet thick.
It will have ice in it, probably light rime ice, although it can be moderate at times.
As we climb through this layer, it will be snowing, the windshield will get ice on
it, and so will the wings, as will other parts of the airplane. We’ll need to have our
anti-ice and deice systems working. The wingtips will appear fuzzy, and we will
see the shredded cloud slipping over the wing. At night, the running lights will be
a fuzzy glow. Then, suddenly, we will notice that the fuzziness on the wingtip has
gone, with the running light bright and sharp, and if we look closely, we’ll notice
that ice has stopped forming. We are still on instruments and in snow, but we’re
on top of the lower deck and between layers. Staying here, we will not get any
more ice, just snow, which doesn’t bother us, because we are not actually in a
cloud. The air will generally be smooth.
Occasionally, we may feel a slight bump, and looking out the window, we may
see a slight fuzziness on the wings and realize we’ve picked up a little ice. What
happened was that we went through a portion of cloud. In doing so, we probably
encountered temperatures that were fairly close to the freezing point. This little
cloud is just a piece floating around in a whole mess of temperature change and
moisture, trying to form a large cloud mass, but it hasn’t quite got the right
formula, so the water vapor turns directly into snow. The lower the air
temperature, the truer this will be; that is, the colder the air, the less cloud.
Thus we can form another rule that says, “If the temperatures are near
freezing, warm fronts are dangerous things and should be considered very
carefully before being flown.”
At higher levels in this vertical cross-section we may find another cloud deck;
but it will be high, 14,000 feet or more, generally composed of ice crystals, and
will have only light rime ice. If this deck has more than light ice, you are probably
in the slope of the frontal surface. Go down to get back in the unclouded snow, or
if the airplane climbs well, go up to where it’s too cold for much ice. This will be
above 18,000 feet, perhaps 25,000 feet.
It’s wise, also, to keep the surface and lower-level temperatures in mind,
knowing that if they are a region of above-freezing temperatures, there will of
course be no ice; and a place to escape. It’s pretty silly to sit up high fighting ice
when one could be lower in above-freezing temperatures.
Sometimes this other cloud deck actually doesn’t exist. I (RNB) remember
one time flying in moderate snow at 8,000 feet, on instruments but not actually in
a cloud. For curiosity’s sake I climbed on top. The top was 25,000 feet, and at that
altitude there was only blue sky above. During the entire climb, the airplane never
went through any actual cloud, but once on top and looking down, the stuff below
seemed to be definite cloud, like the top of a stratocu deck. Descending back into
it again, I saw it was only snow and haze, with no cloud and no ice.
Now, as the frontal surface approaches, cloud becomes more frequent. If there
is a top deck, it will eventually merge with the lower deck, resulting in a fairly
thick cloud deck. Here is where the front becomes interesting, the ice problem is
in that wall of cloud. The lower the temperature, the less ice; but just for
meanness’ sake Nature fixed it so that we can get ice at pretty low temperatures.
It’s the moisture content that really counts. In days past, we could have received
that information from a meteorologist, who would take a look at the radiosonde
observations, giving a pretty good idea of how much moisture there is aloft. Of
course, as we’ve said, the chances are slim that we can talk to a meteorologist, so
what then? It will be in the forecast, whether text or graphical, which will simply
tell us where and at what altitude ice is expected. If there’s lots of moisture and
conditions are right for ice, the forecast may call for severe icing. That’s the
modern, computerized way of saying how much moisture is in the sky. It doesn’t
give us a “feel” for it, and they may include a fanny-saving fudge factor to be
conservative, but we cannot count on that. Anyway, it’s on the safe side, and if the
forecast says ice, it will probably be there. Lastly, if we do have any interest with
in-depth weather analysis, today’s computerized world gives us access to
radiosonde data with the Skew-T log-P charts. That’s where we can find
relationships of temperature and moisture helpful for predicting where enough
moisture may exist for ice; however, it’s localized data for each location where the
Skew-T log-P is located.
Generally, the distance through this walled area isn’t very great, but it can be
far enough to give a load of ice that’s very troublesome. The easy way is to go on
top of it all, climbing until it’s CAVU above. Unfortunately, the tops of these
conditions are very high, in the area of 30,000–40,000 feet, where we obviously
need a high-performance airplane. The more laborious way is to barge on and see
what happens, but first the pilot should be pretty certain not to be flying along the
front, instead through it via the shortest distance. We get this information from
either the weather map before takeoff or onboard our aircraft through data link.
Then we study the location of the fronts and the probable direction we’ll go
through.
Fishing to Get Out of Ice
In flying up to the front, we’ve stayed at a level that is pretty much cloud-free.
That comes from old Rule Number One: do something about ice when it first
forms. If we are flying in snow without ice and then ice suddenly forms, we start a
fishing expedition by climbing if we’re at a low altitude, and perhaps descending
if high, carefully watching the wings during the climb or descent until we’re out
of cloud, noted by the lack of fuzziness. This climbing and descending will
depend on the temperatures. If it’s very cold, it will only take a little altitude
change to get out of the cloud, perhaps as little as 500 feet. As the temperature
increases, that cloud will get thicker and perhaps run into thousands of feet.
When we learned these things, and experimented with them, it was the era of
DC-2s and DC-3s. There was very little ATC anywhere, so one could change
altitude and fish up and down, sometimes only a few hundred feet or so, without
asking for or getting a clearance, a happy time. Today, of course, we need ATC
clearances before changing altitude, unless it’s an emergency, and then we must
announce it as soon as possible.
So now, back to the frontal surface. As it is reached, climbing or descending
will be a waste of time, because things are pretty much total cloud, unless we
know that there are above-freezing temperatures below. The pilot ought to know
where the frontal surface is apt to be in order to avoid climbing or descending
when it is useless to do so, and by the same token, not just sitting at one altitude in
ice-producing cloud before getting to the front. All this again means a careful
study of the weather map and weather reports before takeoff, then keeping
updated in flight, so the pilot can decide where the front is, what its past
movement has been, and where it will actually be when we finally get to it.
Another way of telling when we reach the front is by the precipitation—it will
probably increase considerably and the clouds will also be more turbulent. If the
precipitation becomes heavier, the air rougher, and the cloud thicker, you have
reached the front.
Now it’s a question of going through and hoping it isn’t too far. The best out
now (an out is something no sane aviator takes off without, having it carefully
thought out before departure) is a 180° turn. We can poke on in there and start
getting ice. We know what’s behind us and where to go in order to stay out of ice.
Now it’s a question of deciding how much ice we are willing to take on before
turning around. This amount must be divided in half, because if we go in and then
decide to turn around, we’ll have to go back through that much again. Most times
it isn’t too far through, but it’s something that makes us sit on the edge of the seat.
Once through, there will be an abrupt change of some sort, the turbulence will
stop, the precipitation will let up, or we may break out between very definite
layers, maybe even on top. Once a pilot feels they have crossed the front, it’s time
to fish again for a top, a layer, or something ice-free.
Taking Off in a Front
It can be dangerous to take off when a front is very close to the airport. We are apt
to climb right into a mess that we don’t know much about. It’s best to wait until
the front passes, then sneak up on it knowing a little about the stuff that defines its
character.
Learning Time
All this talk has been about fronts that have below-freezing temperatures
throughout. In spring and fall, however, fronts have above-freezing temperatures
in various places, and while this sometimes helps, sometimes it makes matters
worse.
If there are above-freezing temperatures in lower levels, it’s a good time to
play a little. That way, we can descend and melt off the ice. It’s a good day to fly
high and find out what makes up these fronts. Before takeoff, a close study of the
weather maps, METARs, and icing forecasts will give us a good picture of what is
happening and where we’ll find the above-freezing conditions. Now we can go
play.
However, above-freezing temperatures can also be dangerous. Suppose the
overrunning air is above freezing and it’s overrunning below-freezing air. The
precipitation will be rain, except in the lower levels. Then it will be freezing rain,
and that’s nasty stuff.
Orographic Effect Again
The thing that complicates all the frontal business is local-effect orographic
lifting. With the extra help of air being lifted up mountain slopes by the wind, the
air can hold lots more moisture. When air is lifted that way, it can produce severe
icing at very low temperatures. Take a cold front over the Allegheny or Cascade
mountains. It collects lots of extra moisture that is pushed up the windward side of
the mountains. That means more ice.
These orographic effects are peculiar to various regions, and unless we know
the region, we must guard against them. This is where meteorological help comes
in, whether from asking a weather office or even local pilots about orographic
effect. With no meteorologist or local pilot knowledge, we inspect the prospects
on our own, using personal knowledge of meteorology and its basic rules: One,
are there mountains to cross? Two, is the wind flowing up the mountainous
terrain? Three, is the wind circulation coming from a source of moisture like the
Pacific Ocean or Great Lakes, and even smaller bodies of water, such as Lake
Champlain affects Burlington, Vermont? If all the answers are yes, we can be
certain there will be lots of ice in the clouds and either be prepared to cope with it
or sit on the ground. Always be extra cautious with ice and fronts when in
mountainous terrain. If we’re in a part of the country that’s new to us, here’s
where a broad look at a sectional chart can give us a feel for terrain and weather,
as can a good chat with a local pilot.
Cold Front
In flying fronts, the problems are pretty much the same whether the front is cold,
warm, or occluded. A cold front is more violent, quicker to get through, rougher,
and has more ice. The warm and occluded fronts are a little slower but cover a
larger area and make you sweat longer.
Ahead of a cold front there is a high deck, with some layers below, but it’s
generally easy to maintain a position out of the clouds and, of course, out of the
ice.
As we fly into the front, ice will be plentiful. Cold fronts are unstable, with air
being lifted quickly, and therefore carrying considerable moisture. Consequently,
the ice can accumulate on the aircraft in heavy amounts and can do so quickly.
However, the distance through this area is relatively short. The danger, or
rather the mistake often made, in passing through a winter cold front is staying in
the stratocu deck that forms behind it. The front itself may have been passed
through, but the airplane remains on instruments, getting ice. Actually, a couple of
thousand feet higher might put the airplane on top, in the clear.
To avoid ice, cold fronts can be flown higher than warm fronts. We remember
that the lower the temperature, the less potential there is for ice, so flying up high
will help. Then, when the actual solid part of the front has been traversed, there’s
a better chance that the airplane will be on top of that lower stratocu deck on the
backside of the front.
Flying weather of this type is like learning to play the piano. It takes time. A
pilot must study the weather carefully and then begin crawling before walking.
There are certain days when we can poke into these things, seeing what they are
made of, and still leave an out or two. For example, when overrunning air causes
an altostratus deck, the weather is simply high overcast, with the weather at the
airport good. That’s the day to go on up there and poke into that altostratus, then
fly a while toward the frontal surface, eventually turning around to return home
and mull it over. When any opportunity like that presents itself, we should use it
as a valuable learning experience.
Flying to Feel Ice
Let’s summarize a bad situation we have picked at throughout this chapter. We
stayed in icing conditions too long, and the aircraft has too much ice.
When ice begins to change the important aerodynamic shapes of our aircraft,
it not only increases drag that affects things like stall speeds, but also influences
the aircraft’s stability and control, as well as related handling characteristics.
Because each ice experience can offer different changes to our aircraft’s shape, we
are faced with an undefined variety of flying characteristics and handling.
This issue leaves us in the dark as to what we can expect from our airplane,
but we add speed to landing in hopes of counteracting poor stall characteristics or
maybe use less landing flap to avoid stability and control issues. What else can we
do or do we need to think about?
First, it’s obvious that if we have a lot of ice, we have that undefined airfoil
shape and all sorts of drag. Our airplane needs more power than available, and
probably stalls at some lesser angle of attack with unknown characteristics, and
very possibly before the stall warning will work. The airplane has to come down.
If we keep enough speed, which really means keeping our angle of attack below
that of stall, we can at least crash under control; if we break out of cloud with
enough altitude to find a place to go. Grim prospect.
Another consideration is that many icing accidents seem to occur in descents
or landings. In these phases of flight, we’ll slow for a holding pattern, and
eventually the landing itself. This means we are increasing our aircraft’s angle of
attack, approaching that unknown stalling point. The airfoil change may also
cause an asymmetrical stall, so the airplane will fall off on a wing, heading for a
spin. Remembering the explanation of SLD icing, the aileron “snatch” is a result
of too high an angle of attack. If we had been using flaps and then retracted them,
the angle of attack will increase and possibly cause at least stall buffet, if not a
total stall; if there’s time, we may be able to put the flaps back to where they
were. In all these stall events the recovery is still the same; get the nose down and
the airplane flying, but if we go off on a wing, we’re probably looking toward a
spin recovery technique, hoping the ice-covered airplane will still respond as it
would clean. Also, we hope we have enough altitude, as well as instrument flying
ability, to do this on the gauges.
Another event that is rare, but does occur, is stalling an iced up stabilizer.
Usually this occurs with flap extension. With the horizontal stabilizer normally
lifting downward, the flow off the flaps creates an angle-of-attack increase on the
stabilizer’s top, it stalls, and pitches the aircraft down, usually quite violently.
Low to the ground, the chance for recovery is slim. This stall is totally different,
requiring us to pull back on the control wheel or stick—often with very strong
force—and immediately retract the flaps. Adding power is not always helpful,
depending on an airplane’s power-pitch effects. If that solves the problem, leave
the flaps up. This is a main reason we consider leaving flaps retracted for landing
an iced-up airplane, especially light-to-medium general aviation designs. For
more on this tail-icing issue, we again recommend NASA’s SLD and In-Flight
Icing Training media, as referenced in the Suggested Reading section.
Aileron snatch and tail stall aside, a more normal concern is flying in icing
conditions with an autopilot. It can hide two important things. One is any major
handling characteristic changes. The autopilot will mask these changes, or it will
until the autopilot cannot handle any excessive control pressures, and then
disconnects. At that point, the airplane is off and running, and we’re grabbing for
controls that are racked to some limit; at the same time, the airplane may be off on
some aerobatic event. And we are on instruments, where no autopilot, Flight
Director, or guidance boxes will do us any good; we only have basic instrument
indications and hand-flown response.
If we hand-fly the airplane in ice, or at least off and on during cruise, we feel
the airplane; both in handling as well as its stability and control tendencies. If our
controls tell us of vibration or lightness in any axis, we need to define which
controls and think accordingly. For example, ailerons may be an ice ridge
problem, requiring us to keep that speed up for less of an angle of attack. Or a
pitchy, light elevator that is hard to control and tends to pull forward may be
warning of potential tail-stall issues; don’t put the flaps down for landing and
keep the speed up. Overall, hand-flying lets us feel the whole airplane: Is it
mushy, or does it yaw, or roll back and forth? Maybe it feels like we’re sitting on
a greased flagpole, on a windy day, with springs tied to our rear ends. Sounds
inappropriate, but when you’ve flown an airplane that feels like this, it’s a very
graphic description of an uneasy condition.
So if we have been flying in ice, it’s a good idea to hand-fly for at least
occasional periods during cruise and initial descent, allowing us to feel any
changes to our aircraft’s handling characteristics. However, when it comes to the
later part of the descent and landing, it’s also a good idea to consider hand-flying
the whole event, minimums weather allowing. And the same goes for takeoff into
icing and the climb through it; if we really want to do so in the first place. Such is
another reason to stay sharp with our hands and feet.
Coming Home
We’ve flown through ice, made a letdown, and now have the runway in view. The
flight is about over, and we’ve got it made. Well, we really haven’t, of course,
because that runway may be contaminated with ice or various types of new or old
snow cover, and maybe a gusty crosswind, too. Now what? First, we find out as
much as we can about the runway condition, especially braking reports. We define
that in Chapter 19 , but let’s assume the braking is supposedly lousy. We’ll land
short—or at least hit our touchdown spot and not float—in order to have as much
runway as possible for braking, but not so short that we undershoot. It also is
worth touching with a bit of firmness, especially if there is standing water to help
prevent hydroplaning. If there’s a crosswind, we’ll use proper technique,
including rolling into that upwind wing and making the same timely and concise
rudder movements, as we did taking off on a slippery runway. Once on the
ground, we want to try the brakes gingerly, feeling what’s there. This needs to
happen early in the roll-out. Without an anti-skid brake system, as in most general
aviation aircraft, the best braking comes from the on-and-off method talked about
earlier. Larger aircraft that are equipped with anti-skid brakes allow us to push on
the brakes and allow the system to take care of this off–on business automatically.
Modern automobiles have anti-lock brakes, which, to a degree, are the same thing.
The moral is don’t try to cycle the brakes, because it messes up the anti-skid,
potentially making things worse. Just lean on the brakes, and if you feel and hear
the “thump-thump-thump” of their cycling, stay on the brakes and let them do
their thing. Really high-end aircraft have automatic braking that goes into action
on touchdown and brings the airplane to a stop without the pilot doing a thing.
There’s always a question about how far to go with aerodynamic braking; that
is, using flaps during the landing roll or trying to keep the nose wheel up in the air
and the tail down so that the entire airplane is creating drag and slowing down.
This is worth investigating in our aircraft’s flight manual or fiddling with it on dry
runway days. There is concern that not having the nose wheel on the ground and
helping to stabilize the landing rollout, especially in a crosswind, makes things
dicey.
It’s a known, established fact that the fastest braking comes from wheels in
contact with the ground. This means that one should get the nose wheel on the
ground gently, and the airplane’s weight on the wheels, where the brakes can take
over. Of course, if the aircraft has spoilers, especially jets, they need to be
extended. Some like the idea of retracting the flaps to reduce lift, hence more
weight on the wheels. The flap-retraction issue meets with serious debate, and
frankly we feel is a bad idea on a retractable landing gear airplane; you guessed it,
moving the wrong lever in the heat of battle. In fixed-gear airplanes, especially if
that is all we fly, it may be worth considering, especially if a classic old-timer with
quick-operating, manual flaps. Another benefit of flap retraction on contaminated
runways, especially slushy ones, is protecting the flaps from stuff being thrown
off the wheels and onto the flaps. And remember the appropriate braking
technique. Lastly, this is usually not technique for higher end aircraft, especially
large and turbine powered ones.
If the runway is sheet ice, there may not be any brakes at all until one is
moving quite slowly, and then braking will be marginal, at best. So it would seem
that aerodynamic braking would be best; that is, we should get as much as
possible from it. But if a runway is that slick, then we really don’t have any
business landing on it. We should go elsewhere, if possible.
The facts say to get the weight on the wheels and get stopped, but there may
be a few times when this won’t work. We cannot make a rule. This is where
judgment backed with knowledge takes over. Pilots, hopefully, will always have
to make judgments; it wouldn’t be a very interesting game if they didn’t.
Of course, we must not forget the luxury of reversible thrust, whether jet or
propeller, making a safe and graceful stop more likely. In the case of a jet,
remember the reversers are most effective at higher speeds, so get them in action
as soon as possible after touchdown and don’t be bashful with the thrust.
However, in crosswinds, it is important to remember that crosswinds can make an
aircraft laterally unstable, especially ones with tail-mounted engines. What
happens is that some configurations of tail-mounted engines find the reverse
thrust blanketing the fin and rudder, effectively reducing its size and stabilization.
The crosswind starts us weather cocking, then the aft thrust vector also develops a
side vector in same direction as the wind’s effect. Good old vector-analysis from
math. Usually the solution is taking out the reverse thrust; if this is not done
quickly, we’re very possibly going for a sideways ride down the runway. If we do
get into one of these “excursions,” but through some fancy footwork get the old
bird straightened out, we want to keep it straight from where we are on the
runway, and not steer back to the centerline. That effort may set us off on another
wild ride.
Let’s say we are well slowed down on the runway and feeling pretty good
about it. Now another little hazard creeps in: turning off the runway. It’s often
tempting to turn off as soon as possible if there is landing traffic behind us that we
don’t want to hold up.
Too fast a turnoff on a slick surface may find us going sideways into a snow
bank. One must proceed slowly on icy surfaces. Generally speaking, we may be
rolling along at a faster rate than thought. The bigger and higher off the ground the
aircraft, the more this effect occurs; thinking we’re only doing 20 miles per hour
may actually be 40. We turn off the runway onto a taxi strip slowly, even if the
tower is yelling at us to clear the runway; if runways are slick, then ATC had
better give a little extra spacing between landing aircraft. Normally, however, they
don’t, especially at bigger airports, so if on our landing roll the turn off looks
dicey, especially if we’ll miss a taxiway they asked us to use, we need to let them
know as soon as possible; that airplane on short final behind us will prefer a goaround at 300 feet, instead of 50 feet.
As we park the airplane, it’s important to be certain the surface is not so slick
that our airplane will start sliding after we’ve left it. Surprisingly, too, pilots
sometimes hurt themselves when getting out of the airplane and setting foot on an
icy surface. Our minds are apt to be full of reflection on the flight, and the landing
just made, so we are not mentally back to earth with enough sense to think about
such details as ice on the ground. An undignified fall with a broken bone or two
would be too bad, especially after flying safely through all that weather and ice!
17
Taking Off in Bad Weather
Now let’s talk about the three parts of a weather flight: takeoff, en route, and
landing. We have studied the weather in earlier chapters. We’ve made a flight
plan, picked a surefire alternate, and decided on fuel. The airplane has been
preflighted. It’s ice-free, and the pitot static ports are free of any obstructions.
The charts we need, whether primary navigation or backup to electronic,
should be arranged in order and placed where we can reach them easily in flight.
Our portable electronic devices have been efficiently arranged, without wires
hanging everywhere or blocking out the windshield. These portable devices, along
with any programmable aircraft electronics, have been loaded with necessary
information and carefully verified; if we have someone flying with us who is
willing and capable, we can have them verify this data input is correct. We’ve
studied our flight’s routings, including departure from the terminal, en route, and
arrival at the destination.
There’s a pad and paper handy, and perhaps a kneepad. If the airplane has an
intercom system, we are wearing a headset with a boom mic. We do our normal
checklist and again verify our navigation, and that each radio is set for the
departure. If there’s an ASOS, AWOS, or ATIS, we’ve listened to it, set the
altimeter, and brought pertinent information into our departure plans.
Altimeter Setting
If there isn’t an ATIS or ASOS/AWOS, we try to get the wind and altimeter from
any official source, otherwise as accurately as possible to the airport’s elevation at
the point we’re located. Altimeter setting is very important and should be set
before takeoff. If there is an official choice, we don’t just set the altimeter to the
field elevation and think that’s okay; we prefer that official altimeter setting. This
checks the altimeter’s accuracy by noting whether it reads the field elevation. If it
doesn’t, then our altimeter’s accuracy is suspect, and we’d better dig deeper. First,
get a repeat of the setting, and if that doesn’t correct the problem, it’s time to go
back to the shop.
If we are depending on VOR navigation, and there’s a VOR Test Signal (VOT)
on the field, the ship’s receivers should be tested for accuracy. We want to make
sure the GPS system has sufficient satellite coverage, accuracy, and a current data
base. If we are using an ADF, we should be certain to check all its functions:
antenna, manual loop, and pointing to the station when in automatic.
Be Prepared
When we take off, especially at night or in instrument conditions, it is nice to have
a navigation aid quickly available to aim us back toward the airport. In years past,
when ADFs were still commonly used, unless part of the departure procedure
we’d tune the ADF to the Nondirectional Beacon (NDB ) at the outer locator of
the ILS runway being used for landing; assuming, of course, the airport had one.
Or we could have something set up on the second VOR/ILS. Today, using GPS or
IRU systems, it’s a “direct to” selection to find the airport, or an instrument
approach is stored and ready for hasty return. All this is for an emergency
situation, in case something serious happens right after takeoff, such as a fire or
engine failure, and we want to quickly return. We would know which way to head
while telling the tower we’re in an emergency and need immediate return.
Unfortunately, the FAA is removing the NDBs, so no matter how diehard we may
be on flying old-school, the end of most NDBs is on the horizon. And for all this,
we have checked which runway and approach is being used for landing, as well as
the approach’s inbound heading and altitudes.
This is all planning for, we hope, a far-fetched possibility, but it’s this kind of
detail that is part of aviation’s nitpicking. Like so much of this thinking and
preparation, it may be rarely needed, but can make the difference between an
interesting event versus an unfortunate one.
Let’s Go
Now we start up, set up whatever is left in preparing our aircraft, and only then do
we call for our airway clearance. Of course, we might want that airway clearance
before start, if it will take time for the clearance to come through, or will cause the
fiddling with route programming typical of electronic cockpits. When the ATC
clearance comes through, be ready to copy it on a piece of paper—the kneepad
again. Never leave it to memory, even though there are useful acronyms to help us
make sure we have all that is required. After it’s copied, we read it back. After
that’s done, let’s absorb the clearance. First, mentally picture the route. Be certain
the avionics and navigation systems are set up and ready with the correct courses
and modes of operation. Then, we firmly implant in our minds the altitudes and
headings, as well as any unique departure procedures and initial selections needed
for electronic navigation.
There are a couple of benefits to getting our airway clearance before engine
start. One reason is that electronic navigation, instrumentation, and aircraft
preparation tends to keep our heads down in the cockpit, while programming and
checking our clearance’s routing, which isn’t clever sitting on the ramp with an
engine running; especially, if there is only one of us on board. A quiet aircraft lets
us concentrate on all the clerical stuff without a nagging, running engine. Worse is
being rushed then taxiing the airplane while trying to do all this stuff. Nor do we
want to set up an initial routing, betting on finishing the job once airborne.
It is very important to understand the routing of our flight, whether using
maps or electronically displayed routings. We want to know where we’re going
and have our maps folded, marked, and in sequence. This is especially important
when flying in unfamiliar areas. Once while a new and “adjusting” captain, the
airline had sent me (ROB) to fly an intra-European trip, the routes recently
acquired through a merger with another airline, and an area where I had never
flown. We were leaving some place in Eastern Europe, where getting all the
procedures and maps together was extensive; we were in a 727 with basic
instruments, which was nothing more than any analog-instrumented light aircraft.
On the taxi to takeoff, the departure procedure and initial routing still felt vague,
despite earlier review, especially the navigational aids of mysterious names and
location. Even though the copilot and flight engineer were more familiar with the
area, it was important to have the whole crew on the same page, especially the one
who gets yelled at if something goes wrong; the pilot in command. So, we pulled
over on the ramp and reviewed the whole fandango one more time. To heck with
schedule.
So, after we have our clearance and everything is ready to go, it’s worth
having a departure briefing; not a taxi or before-takeoff checklist, but a briefing
that goes over key items affecting a departure. Years past, much of this kind of
fell in with our before-takeoff thinking, but those simple days are gone; there is a
lot of stuff to remember these days, and it is easily confused or missed. Some
departure briefing items we like are below; obviously folks will hone them for
their needs:
• Weather:
• Winds, temperature, and density altitude.
• Takeoff and return landing minimums.
• Sky—wind direction, shear, turbulence, and thunderstorms (radar use,
deviations, should we takeoff).
• Environmental—cold/icing or hot weather.
• Taxi:
• Review taxi route and congestion issues.
• Runway:
• Length, surface type and condition.
• Slope and initial obstacles.
• Terrain:
• As effecting takeoff and climb to cruise.
• Takeoff Procedure:
• Initial turns, headings and altitudes.
• Aircraft clean-up.
• Automation—when planned to engage and initial functions.
• Abnormals:
• Engine loss;
• Return procedures and navigation;
• Aborted takeoff criteria and procedures.
The idea of the departure briefing, maybe at best a short but concise checklist,
is to pull the whole takeoff and initial flying event into a homogenous package.
The above example may seem lengthy, complex and time consuming, but like so
many things, once it’s a habit, the process is much quicker. This departure briefing
would best be reviewed before we start the engine/s and begin to taxi, if at all
possible. Also, even though many of today’s aircraft, especially single-engine
ones, are not intrinsically complex as just basic airplanes, we’ve made them so
with all the electronic systems and ATC environment. For such aircraft, the days
of “kick the tires and light the fires” are over.
Radio Thoughts
Usually, we will change frequency after takeoff, so we want that set up
beforehand. If we don’t have a dual frequency preselect on our radio, we need a
firm note of this frequency; the best is to write it down as part of the clearance.
Right after takeoff is a busy time, especially for a single pilot hand-flying IFR,
and if we somehow miss that frequency selection, it’s a bad time to be chasing
around for the correct one. Also, once in the air, when new communications
frequencies are given, if we do not have those preselect radios, we should still
write the frequencies down. In this way we’ll always have the last frequency. If
we then call on the new frequency and there isn’t any response, we’ll know what
frequency to go back to. There’s nothing more frustrating than tuning to a
frequency, discovering it’s a dud, and then asking yourself, “What the devil was
that frequency I just left?” We had to do this when I (ROB) started my career, and
after a long flight you’d have 30 or more down the list, but this saved us from
moments of wrong frequency or slipped numbers, more than just a few times. It’s
an old technique, but not everyone has all the latest equipment.
Once we do take off, if we have a choice, let’s not be hurried about changing
to departure control, or talking with whomever we need to. Today, a tower will
usually tell us when to switch frequencies. If for some reason the tower takes a
long time in advising us, we should ask them before switching; they may have a
plan for us based on the ever more complex ATC system. If for some reason the
frequency switch is at our discretion, there’s a tendency for pilots to feel they must
change as soon as the wheels leave the ground. Well, the most important thing
right then isn’t departure control; it’s flying the airplane. Before changing
frequencies and talking on the radio, let’s get squared away; power set, flaps and
gear cleaned up, electronics selected and aimed correctly, all settled in a peaceful
climb. A copilot, of course, makes all this easier and faster. But always, as in
everything we do, the first thing is to fly the airplane.
Good use of radios will make frequency changes easy if we plan in advance;
but we’re all human and occasionally dig ourselves a hole. What we do is have
that preselect frequency selection, and/or two communications radios, with one
set on the tower and the other on the departure control frequency, and so forth,
throughout the flight. After takeoff, when they say to change to departure, simply
flipping the control panel switch to the other radio gets it done with a minimum of
distraction. When no one is home on the new frequency, we go back to the old one
and tell them no one loves us on their new frequency. Every once in a while, after
a really long day, we’ll screw up and tune the wrong window, then about the last
digit of the number we’ll forget it—and also the frequency we were just talking
on. Now we grab maps looking for ATC sectors or fiddle on an MFD screen; of
course not paying attention to flying the airplane. It happens so easily …
Taxi Time
As we taxi towards our departure, we’ll eventually run through a checklist that
reviews, among other things, the altimeters, flight instrument, and navigation
aspects of the departure; extremely important items that aim us in the right
direction and keep us from running into things. Call it part of a taxi-checklist, as
was the case in more complex aircraft, or maybe it’s all part of the before-takeoff
checklist for our personal airplane. We can do it while we’re taxing, but for a
single pilot, if we can run through the list while the airplane is stopped, it’s a much
better deal. Even in two-pilot operations we’d hold off when the taxi process was
hectic.
A technique for reading this checklist first came my (ROB) way from a superb
mentor years back. Our checklist said: “altimeters/flight and navigation
instruments.” Although we were supposed to say something like: “Set and crosschecked,” after quietly looking things over, instead he’d point at each respective
instrument, selection window and radio, check it with the written clearance, and
finally verbalize the correct setting; and end the process with the required correct
checklist response. (Remember, everything we say in an airliner is recorded.) This
would include: altimeters, initial altitude, departure control frequency, transponder
code, initial heading, and initial course, as referencing from whatever instrument
needle and radio. As we went from the analog simplicity to electric jets, we’d
discuss what was going to happen with electronic mode selections and related
navigation; and time proved this verbalizing, especially in the glass-cockpit
world, is a needed standard. These are important checklist basics we deal with on
departure, as well as other phases of flight, which allow one to verify not just an
item, but by confirming that it was set and verified off written clearance. It also
helps it sink into our minds. A lot to say for a checklist, but when the process is
habit, it doesn’t take long. Also, right after takeoff is not the time to be trying to
read written clearance and fumbling with selecting a frequency or whatever,
because it was not verified before departure.
The taxi-checklist also covers certain system operations, such as the important
flap and trim settings, as well as having things like the pitot heat on. As mentioned
in another chapter, the pitot heat is important, especially in aircraft with EFIS
equipment, and it could be critical to forget it. We also remember that some pitotheat systems are not approved operation while still on the ground, so we need a
reminder, such as a “final items” checklist, that’s used just before we start our
takeoff roll. Lastly, during the taxi, check to see that the DG, heading and attitude
reference, as well as the turn indicator, are working and indicating turns in the
proper direction.
After the checklist we then mentally review the flying process we’ll follow
during and after takeoff. This means visualizing the takeoff and departure, then
making a quick review of the basic stuff like, “Lift off, up gear, climb at ____
indicated. Change to departure control. Up flaps at ____ speed (or before ____
maximum flap speed), set power. Right turn to one five zero. Level off at three
thousand,” and so on. Here we have taken the data from the pragmatic taxi check,
and brought it to life.
The point is to mentally preplan, to know in advance. We don’t just fling
ourselves into the air and then begin to think what to do. It’s all part of the
important rule about flying; plan well ahead of the airplane.
Don’t Be Bashful!
Of course, the tower, departure control, or en route ATC may suddenly change the
routing or altitudes, and we have to be quick and flexible. Write it down and then
visualize it; this, of course, is made easier if we’re looking at an MFD with
graphical route display. Verify waypoints, route continuity, and so on. If there is
the slightest doubt, ask ATC for clarification. Don’t be bashful! A neat cockpit
with handy charts, whether for primary navigation or backup to electronic
navigation, is also important. It makes it that much easier to look up some
intersection, VOR, or waypoint that’s unknown to us. There isn’t anything wrong,
either, with asking ATC where the heck the intersection or station is, especially if
we’re trying to figure out some waypoint’s spelling that we’ll put into a digital
navigation system. As mentioned earlier, if we can’t find it or make the
assumption it’s spelled one way, but we’re wrong, that wrong direction turn, even
for a short time, could spell big trouble in mountainous terrain or crowded
airspace. High-profile and tragic accidents have been caused this way.
When we use VOR as it used to be, each time we tune to a station we’ll use,
we must be certain to identify the station’s Morse code identifier and to have the
identification sink in; we should not just listen to random dots and dashes.
Embarrassing things have occurred due to a failure to identify, such as a pilot I
(RNB) knew who tuned Orly Airport’s ILS in Paris, France, shot an approach to
300 feet, and landed, only to find he was at Le Bourget, all the way across the city
to the north! He failed to identify the ILS. Sadly, things have happened with more
serious consequences, so identification of any aid before use is very important.
With modern GPS navigation systems, we can be so easily swayed that all the past
is gone and forgotten, but if we use any part of older systems, then the past is still
here.
If we are flying an older instrument panel using VOR navigation and maps, it
is very easy to become complacent about this, because the numbers on radio dials
are clear, and there isn’t any fishing and tuning; we simply turn the dial to the
number, and that should be the station. Mistakes can be made: we looked at the
charts for a frequency and set it up, but in the chart confusion we read the
frequency for a different station; frequencies are changed, and we may have
missed the NOTAM that supersedes the map; or we may not have the latest chart
revision in hand. Another one that will get us is an airport using the same
frequency for opposing ILSs on the same runway, the only differentiation being a
different identifier. If we just happen to be the lucky folks who show up when the
landing direction is swapped, but the control tower forgot to swap the ILS
frequency, it can turn into a real mess. We’ve had it happen, but fortunately the
identification caught it. All these, and more, have caused wrong tuning and
accidents. Even our home station, which we know so well and, perhaps, are
looking at right over the nose, should be identified. It’s a habit, and once it’s
ingrained, it isn’t a big deal.
Altitudes are also tremendously important. When given an altitude clearance,
we should write it down or place it on an altitude reminder. Having an altitude
reminder with a warning sound alert is very advantageous. We get the warning
approaching and leaving the altitude, so this helps when the altitude is
approached, or if we wander off a selected altitude. These are good gadgets, but
the pilot still should keep altitudes firmly in mind and not count on the gadget
alone to do the job. If we are low-tech, there are altitude reminders with numbers
we can set, mounted on the control wheel or instrument panel. It’s a substitute for
writing them down—a good one, too. One technique that came about was
pointing at the selection just made and saying it out loud. Whether altitude,
heading, course, speed, or whatever, the idea is to force us away from the habit of
just setting something without thinking; instead, we take a second look and think
about what we’re selecting, and what will happen next in flying to it. Although
designed for two-pilot cockpits, it isn’t a bad idea when flying single-pilot, aiding
awareness of what we are doing.
One day years back, in a Cessna 182, while weaving through a VOR approach
into Montpelier, Vermont, I (ROB) took to verbalizing the headings, altitudes, and
letdown points. It seemed a good idea as the approach progressed through the
procedure turn, then down between hills that were still hidden by cloud. My
companion was a nonpilot, on kind of a first date. Out of the corner of my eye, I
saw her staring at the nut who was flying her through the clouds and talking to
himself. Even when explaining the reason she seemed skeptical, but the approach
had successfully threaded us between the hills, and that’s all that counted.
Just about all aircraft have Mode C transponders, and now Mode S, that read
altitude. The later Mode S also gets involved with more data, collision avoidance
devices, and the oncoming, at this writing, ADS-B Next Generation air traffic
system. With a transponder’s altitude reporting capability, ATC can catch any
diversion, but obviously the idea is to paying attention to altitudes and not
counting on our Mode C or S, and ATC’s watching altitude for us. However,
checking altitude and the Mode C gives the redundancy desired in all flying,
especially if we are a single-pilot operation. Another aspect of altitude-reporting
transponders is when we fly above 18,000 feet in the United States, and varied
altitudes in other country’s operations. Above these altitudes, we set our altimeters
to standard: 29.92 in. hg. or 1013.2 hectopascals. Then, below these transition
altitudes we set the appropriate altimeter setting. If we don’t, we’ll fly the
previous altimeter setting and level off erroneously. For example, the difference
between 29.92 and 30.22 is 300 feet. That’s not good; we probably won’t hit
anything, but we are getting into violation territory. The words you hate to hear
from ATC are: “Say your altitude.” Busted.
One should anticipate altitudes. If, for example, we’re cleared down to 6,000
feet, we ought to be thinking, at 7,000 feet, “I’m leaving seven; remember, level
off at six.” In other words, climbing or descending, be at least 1,000 feet ahead of
the airplane. If it’s a fast jet descent, be 5,000 feet ahead. In the airline, we had to
verbally say “passing 7,000 for 6,000.” Pedantic, maybe, but history has proven
such is a valid task.
When ATC clears us to a new altitude, we should get right at it and leave the
present altitude as soon as possible, unless, of course, ATC says we can leave at
our own discretion. This is important, because if the cleared pilot fiddles along for
some time, or makes a little halfhearted effort at some minuscule rate that
vacillates between 100 fpm and 300 fpm, it can create a real traffic conflict,
especially in busy airspace. It’s important to get at it, right away. When we fly
with a Traffic Collision Avoidance System (TCAS ), it is a creepy feeling seeing an
airplane slowly changing an altitude, knowing the altitude change they were
supposed to be leaving is where we are going, or may be a crossing traffic issue.
In summation, when cleared, one should descend, climb, turn, slow down, or
speed up smoothly but promptly. If for some reason we can’t, such as when we are
waiting for our aircraft to reduce speed when given a speed reduction, ATC
should be informed.
Off We Go
The tower clears us on to the runway, either for “line-up and wait” or “cleared for
takeoff,” and we swing into position. As we do, it’s time for what some call “the
final items,” relating to where the airplane is supposed to go: heading, altitude,
and airspeed. These items climb and guide our airplane safely through the critical
takeoff and early departure event. These little memory calls not only refreshes our
minds on these important items, we physically and visually should check that
flight-guidance systems have them set in place: altitude warning window, heading
bug on an HSI, and airspeed selected, if the parameter is used.
This is very important with the flight guidance systems integrated into today’s
aircraft. Without proper programming when we takeoff, things can come unglued
pretty quickly, especially if one tries to engage the autopilot at low altitude; if
things are not correctly set, it’s going to take you for a ride. At that point, we
either have a quick electronic fix, or need to disconnect the autopilot and hand-fly
through screwed-up flight guidance indications, remember the heading, altitude,
and airspeeds, make sure the airplane is cleaned up, and talk to ATC, as well as
select and respond to further clearances; like it used to be done! Later, at prudent
altitude and moment, we fiddle with sorting everything out and trying to engage
the autopilot.
If we are departing into low ceilings, we hesitate a moment and let good old
mechanical gyros settle on the runway heading, and with an old DG, we reset the
heading. We’ll check the wet compass, too, but no matter our instrument system,
even the newest slaved electronic ones, we’ll see if they agree with the runway
heading. (This is a good check when landing, too, being certain you’re headed for
the correct runway.)
If the time from startup to takeoff is short, and especially if it’s a cold day, we
may have to delay the takeoff in the run up area for five to 10 minutes, making
sure all the gyros are up to speed. If it’s night, we should be certain the cockpit
lights are set to the most comfortable level, and that our eyes have acclimated to
them.
As we start the takeoff, we’ll make a last-minute check of the few items some
call the “killer” items. The regular checklist should have prepared us well, but it
doesn’t hurt to have a few, most important items that can be checked almost in
one glance. The last check in most all airplanes—from light single to jet, takes a
second or two and really isn’t any different; fuel quantity, pumps on, flaps at
takeoff, trim set, spoilers down, heading in agreement with runway; for a general
aviation aircraft we may add carburetor heat off, prop low pitch, pitot heat on.
Maybe a bit different for a Cub at a country airport, but not much. It’s a habit that
ensures us things that cause serious flying problems are set okay.
In the Stuff Quick
We should have in mind that once we lift the nose and leave the ground, we’ll be
on instruments. It’s no time to worry about flying VFR first and then transitioning
to instruments; be ready at once to be on solid instruments. If there’s good ceiling
and visibility, then, of course, we want to keep an eye out for traffic, but let’s
suppose the ceiling is low, 200 feet or less. Also, most night departures, low
ceiling or not, require reference to instruments more than an outside horizon that’s
poorly defined, if at all.
Going on instruments means going to attitude flying immediately; it means
looking at the artificial horizon. With the ADI pitch bar set on the appropriate
nose-up attitude, at takeoff or climb power for our aircraft, we must be going up.
One should know the pitch attitude for the aircraft at initial climb out and all the
normal phases of flight, then fly them on the artificial horizon as needed. This is
also useful if, for some reason, airspeed indication is lost or obviously erroneous.
So that’s the first step: fly attitude.
If the wings are level, we are going straight, and if one is down, we are
turning, unless we’re handling the rudder like a new student, which we shouldn’t
be. So the position of the wings on the artificial horizon is the other thing we look
at.
With wings level and the nose where it produces climb, we are on a straight
course and climbing. It’s really very simple. If we have to turn, we lower a wing:
30° is enough. ATC doesn’t expect more, and making a steeper turn means more
up-elevator and more concentration that may divert you from other tasks. Keep it
simple.
We first set the attitudes we want and then cross-check the airspeed, heading,
vertical speed, and altimeter. Close to the ground, the pressure instruments briefly
give erroneous readings. On some clear day, watch the vertical speed and
altimeter just as you lift off. Chances are the vertical speed will show a descent
and the altimeter will start down until you are 50 feet or so above the ground.
Airflow over static ports is getting organized, initially giving this descending
input.
Once away from the ground, the pressure instruments settle down, but even
then attitude is the primary guidance and the other instruments a crosscheck. This
cross-check is frequent, however, as part of our constant scanning process.
There is an interesting instrument flying takeoff story we thought you might
like. Ted Hereford, a TWA captain who mentored your first author, was taking off
from St. Louis one night, in a DC-2, during the mid-1930s. St. Louis weather was
low and lousy. His destination, Indianapolis, was clear—thank goodness. Not long
after takeoff, every flight instrument went dead, except the turn and bank. No
airspeed, altimeter, rate of climb, or artificial horizon, just needle-ball. It was not
good weather for a return to St. Louis, and Ted knew the cloud tops were around
4,000 feet. He kept the airplane straight with the turn and bank, then, by recalling
the sound of the RPM appropriate for the two-speed propellers, Ted knew he was
in climb. Once on top, he set the props and their sound for level, flew until it
cleared, then landed safely at Indianapolis, in VFR conditions. The combination
of instruments that failed didn’t make any sense, and TWA could never duplicate
the problem. But you could still see the twinkle in Ted’s eyes, at 95 years old,
when he told me the story in 2001; he was sharp as a tack. Ted’s flown west, and
we sure miss him, as well as his kind, but hopefully folks like Ted inspire us to
really learn how to fly.
How about the Weather?
We are off and away, but so far we’ve talked about flying the airplane; so let’s go
back now and talk about the weather part of the takeoff.
Before takeoff, if we think it’s cold enough for ice, we should have the
propellers slicked up with fluid or hot from electric heating. The pitot heat is on,
as mentioned earlier. If we are flying a jet, engine anti-ice is on, even if the ice
may be in a stratocu deck a few thousand feet above. This takes away something
we’d otherwise have to fiddle with in climb, or maybe forget if we get busy. With
piston engines, we’ll clean out the carburetors with heat just before takeoff and
then remove the heat as we start to roll. But once in the air, we must watch for
engine icing conditions.
Before takeoff, we check the wind direction and velocity. We’re learning about
any crosswind and planning our takeoff compensation. The wind velocity says not
only how fast we’ll get in the air, but if it’s gusty, it tells us whether we can expect
turbulence once we’re airborne. This also makes us think about the wind just
above the ground, reminding us of any shear possibility.
The runway surface is of interest. If it’s winter, and the runway is covered with
standing water, snow, ice, or slush, our ability to stop if the takeoff is aborted will
be reduced, sometimes drastically. The V1 speed is out the window if the
runway’s slippery. V1 is our takeoff “go–no go” safety speed, mostly used with
multiengine aircraft, but a concept worth thinking about, even if not of formal
calculation, when considering an abort of any takeoff. One airline criterion
restricts takeoff to standing water, slush, and wet snow no deeper than ½ inch, and
four inches or less for dry snow. Dry snow is such when the temperature is equal
to or less than 30 degrees F/ −1 degree C. “Wet snow” is obviously above that
temperature, and can be darn near like ice. Another way to unscientifically judge
snow is if we can make a nice firm snowball, it’s wet snow.
On larger aircraft with the data published, we need to recalculate our takeoff
distances required, making sure we have enough runway. With light aircraft at
small airports, the concept is the same. Without published runway contamination
data, however, we should leave a healthy margin: 100 percent of minimum, if we
can.
The combination of a strong crosswind and icy runway calls for care in taking
off. Until enough airspeed is obtained to give rudder response, we’re dependent
on nose wheel or tail wheel steering. Neither has much traction on ice, so the
beginning of the takeoff is a little dicey.
This can be an anxious moment, but things can be improved by lining up on
the runway before starting the takeoff. Swinging onto an icy runway on a running
takeoff is an almost sure way to be partially out of control right from the start.
Getting lined up, stopped, and all squared away before starting to roll is the way
to do it. Don’t let the tower push you into a quick takeoff just because they are
trying to move traffic faster.
Any takeoff, even in very reduced visibility, is started visually. We need
something to grasp with our eyes. If the visibility is ¼ mile or less, we need a
good centerline stripe or, better, centerline lights. Without these, the visibility
must be sufficient to see the runway far enough ahead for guidance. In the
commercial aviation world, their takeoff minimums vary depending on the lights
and markings of runways; and as mentioned before, that’s something worth
considering when flying under FAR 91, where we can blast off into extremely
compromising conditions.
Once in the Air
We need to keep the runway heading, or track, if required by procedure and
available through advanced flight systems, well in mind, and once in the air, fly
that heading until a turn is required. Both landing and taking off in snow, we find
the air choppy and turbulent for approximately the first 1,000 feet. This is almost
always true in snow, because of an unstable condition caused by the release of
heat during nature’s snowmaking process. It isn’t dangerous turbulence, but it
makes an instrument approach or a precise departure procedure more difficult.
Thunderstorms Again
In summer, with thunderstorms in the area, we think in other ways.
Thunderstorms mean turbulence and the possibility of sudden wind shifts. They
mean heavy precipitation, downdrafts, and shear. All this during takeoff, at low
speeds and close to the ground, makes us quite vulnerable. If storms are very
close, it’s best to sit on the ground until we have some maneuvering room to take
off, clean up the airplane and get organized in climb, and then deviate around the
storms.
When we take off with thunderstorms in the area, these are some things to
think about: If we have airborne radar equipment, it should be warmed up and
ready for action. With NEXRAD and/or a lightning detection system, before
takeoff, we can inspect the entire area for thunderstorms, developing our plan to
avoid the area. Most airborne radar equipment has a “standby” position in which
the equipment is ready to go but isn’t actually putting out signals until the control
is flipped to an “on” position; that’s when the antenna begins to search and the
screen lights up. We don’t want it on in the ramp area, where fueling equipment,
people, or other airplanes are nearby, as the radar signal is potent enough to cause
issues.
Fiddling with airborne radar right after takeoff is not the best idea, as our
attention must be centered on the flying business. Takeoff and early climb demand
a pilot’s primary care, so we want to analyze the radar before takeoff, then leave it
be until things are settled down and we have time to fiddle with tilt, range, and
interpretation of the radar data. A good place to park an airborne-radar’s tilt
control, after ground interrogation but before takeoff, is +5°; it’s a good angle for
the radar to start searching at low altitude, when, just after takeoff, we have little
time to adjust it. This discipline applies to any weather-avoidance device.
A two-pilot operation helps, obviously, with the nonflying pilot taking on the
task of radar guru. Such a comment seems sarcastic, but the point is that proper
understanding and use of radar is really a practiced art. If we’re lucky to be flying
an aircraft with the radar data displayed on the PFD or next-door MFD, it’s an
easy display to read, while still flying the airplane. As we look at radar before
takeoff, we’ll often see an escape route around thunderstorms that is different
from where the normal departure takes us. We should have a chat with the tower
before takeoff, negotiating our needed path. It’s so much more relaxed to do these
things on the ground, than in the air while trying to fly on instruments. While we
are ducking thunderstorm cells, ATC has to be kept advised and give us advance
permission for deviations, so we don’t create an air traffic conflict. This is
especially true in a terminal area, where traffic separation can be tight.
On takeoff, when considering how close the thunderstorms might be, we have
to think about the wind, as we could fly into a hefty, gusty wind shift with shear
and downbursts.
Suppose we are taking off south into a strong wind. A thunderstorm arrives
and snaps the wind to northwest; our takeoff run is lengthened, and once in the air,
if we get there, we’ll probably be in downdrafts that will make the climb sluggish
at best and more likely dangerous. It’s a silly time to be taking off, of course, but
sometimes it is difficult to tell just where the thunderstorms are, if they are hidden
in lower clouds.
However, we shouldn’t be taking off or landing with a thunderstorm any
closer to the airport than our rules for normal avoidance in the air. They were 10
miles minimum, and 20 is better. Right after takeoff, the airplane is in poor
condition, accelerating from slow speed after takeoff all the way through initial
climb; a strong shear during this regime of flight is indeed dangerous, being at
best difficult to cope with, or altogether impossible.
Once in the air, we may get some pretty wild turbulence. We want a good
workable airspeed as soon as possible, but of course, we don’t want to shove the
nose down and fly into the ground. It all takes care and judgment.
We should have in mind a direction to run away from the storms if things get
too tough. This refers to an area farther than the terminal area, more so as we
work toward the route of our flight. This knowledge comes from a careful study
of the weather before takeoff, in order to know how the weather is moving. In the
past, we would study the sequence reports for stations in the area, in a 100-mile
circle at least, as well as radar summary charts, to see what was actually
happening. Today, we can look at NEXRAD, even on a personal electronic
device, but also remembering that once we leave aviation weather information, it’s
theoretically not official, and we need be careful of the weather information
source’s currency. This thunderstorm weather is tough, and it shouldn’t be taken
lightly.
Thinking
Now we are in the air on instruments, encased in the tiny world of our airplane,
everything outside ending at the windshield. Let’s not worry about relating
ourselves to the outside, trying to see out there or holding on to that world we
left. It’s best to forget it, settle down, and watch the instruments.
We concentrate on the rather simple job of flying instruments. It is simpler the
more we relax. Lack of worry makes us relaxed, while uncertainty makes us
worry, so let’s not be uncertain; let’s know what we are going to do next, be
prepared, and plan ahead.
Our thinking is in layers. The top layer is flying instruments. But this is easy
and doesn’t require much of our thought. If we’ve practiced enough, it’s almost
automatic.
The second layer is the airplane. Are we doing the right things to keep it
running? Carburetor or engine heat? Power settings, pitot heat on? Fuel on proper
tank, the gear and flaps cleaned up? In other words, all the things that will ensure
the airplane is managed as it should be. If this orchestration stops, so does the
flight, which isn’t a healthy option.
The third layer is navigation. What’s the course we are trying to follow? Is the
station identified, if we’re flying a good old VOR, or is our navigation and
autopilot properly selected and captured, if we have technically advanced system?
What’s the altitude? Are we level or approaching it? That intersection coming up,
are we tuned, identified, programmed, armed, or whatever to have our airplane
properly follow the route? We review all the items that are a part of our
navigation, including flying that heading ATC may have given us.
Layer four is the weather. Turbulent? Fly turbulence methods. Ice? Is all the
anti-icing or deicing equipment being used, and what does the clearance ahead do
for getting out of the ice? Thunderstorms? Are we ready for turbulence, is the
radar or lightning detection equipment working, and do we know a way out if we
want to run?
Layer five is a quick thought toward emergencies. If we want to return, how
will we do it? If we cannot return to our takeoff airport, where’s the nearest place
we can get into?
These layers of function are not precise, nor are all the items listed, but the
thoughts for building your own are there. The layers intermix at times, but once
we get the airplane and engines set, we don’t have to constantly think about each
thing. If the weather equipment is on and working, allowing us to plan far ahead,
this makes the weather issue a source of referenced information, not constant
concern. Emergency action, once it’s implanted in our mind, doesn’t require
attention; it’s there if we need it. Each layer has a priority based on how often we
need to refer back to it.
As we navigate or follow radar vectors, it’s wise to visualize where we are and
what’s under us. We shouldn’t concentrate on this to the extent of neglecting
anything else, but it is particularly important in connection with terrain height.
How high is the terrain and are we clearing it with enough margin?
The charts and routings give minimum altitudes, and we should pay attention
to them. This is a part of preplanning, having a good idea before takeoff of where
things stick up, be they TV towers or mountains. All the fancy equipment and
radar vectors should keep us above the terrain, but in the final analysis, missing
the ground is our responsibility. In the back of our minds should be an awareness
of what a topographic map of the region looks like, especially the heights of
terrain, and then what our actual altitude is; this is now referred to as situational
awareness .
Before we had the many electronic devices that give us navigation displayed
over electronically created terrain, and ATC to lead us around, it was prudent to
have a sectional chart along, even if we were on instruments, navigating with an
airway chart. The airway chart, at best, has a few higher obstacles, rivers, lakes,
and airports, but if we had a serious problem, such as an engine quit or smoke in
the cockpit and so forth, having terrain, geographical, and aeronautical data right
in your hand could save the day. Even today, if our technically advanced
instrumentation runs out of electrons, and despite possibly having a backup
handheld electronic device, just having a sectional tucked down between the seats,
folded along our route, isn’t going to hurt, and it may really help someday. Maybe
a pedantically old-fashioned rant, but that’s our story, and we’re sticking to it.
A good friend of mine (ROB) recently took a check ride with his light twin,
which is all decked out with an EFIS system, technically advanced navigation,
airborne radar, NEXRAD, lightning detection, you name it. The first thing he did
on his check ride was open a sectional chart, fold it along the route of flight, and
slip it innocuously between the seats. His instructor lit up and smiled like a little
kid at Christmas, exclaiming: “I ought to pass you right here and now!”
Radar vectors for departure, en route, or landing, and the altitudes the person
on the ground provides, are supposed to keep us from hitting anything. Don’t
count on them 100 percent. Although truly professional and caring of their
responsibility, no one is 100 percent perfect, and neither are we. There have been
accidents relating to bad vectors, a mistaken altitude call, and so forth. Like a
good crew relationship in a multiple-pilot aircraft, we can work the concept with
ATC and vice versa, which they usually do. Very few incidents have occurred, but
it has happened. When we fly, we’re all interestingly diverse humans, functioning
in an inhuman setting.
In the final summing up, the person flying the airplane is responsible for it,
and missing the ground is a paramount part of the job. In today’s busy air traffic
and regulatory aviation world, ATC folks and pilots alike are constantly being
tugged from aviation’s once simple concepts. However, the ultimate responsibility
is still the pilot’s. Never take anything for granted, and especially not the idea that
a certain heading and altitude given from the ground will clear all obstructions.
This is not always related to just the ATC clearance. For example, a standard
instrument departure we may be flying in a mountainous area may not give us safe
altitude clearance if the aircraft’s climb performance is lower than required, due to
ice, turbulence, wind flowing down mountain slopes reducing our climb, density
altitude issues, and so forth. It’s important to look over the departure carefully in
regard to terrain and not just assume that it’s okay, instead relating to the
departure route versus your airplane’s climb ability. This is published to a certain
point on departure procedures, but eventually we’re out of the area and possibly
still trying to reach minimum en route altitudes with these compromising
conditions.
We must, by any means possible, keep up-to-date on where we are. We must
not simply sit there, wandering hither and yon, following the vectors, and not
knowing where we are in relation to terrain. The controller may be giving
headings, but the pilot is responsible for the navigation. Navigation is made up of
many things, and one of the biggest is keeping position information and knowing
where we are. A heading is simply directional information. Where the aircraft is
and keeping it clear of all terrain is always the responsibility of the pilot in
command.
18
Weather Flying En Route
Now we level off at cruising altitude; sit back, and relax a little. The intense
concentration of an instrument departure is over. This is the time to look around
the airplane, checking that all is in order. We glance at all our systems; especially
things like the fuel setup, making sure things are functioning as needed, such as
pitot heat, engine heat, and deicing equipment. It’s a good idea to start on one side
of the flight deck and cover everything to the other side, going across the
instrument panels, and occasionally taking a peek at those obscure places, like
hidden circuit breakers.
If we are navigating with charts, they and numerous papers from takeoff
preparation and event are probably mixed up, and this is a good time to get them
organized and neat. The same goes for those charts we had between the seats,
ready for backup if we are using electronically displayed navigation. Now there is
an opportunity for writing down the takeoff time and the time a fuel tank was
switched on as well as the other bookkeeping jobs. Knowing when fuel tanks were
turned on, takeoff time, and maybe even with EFIS systems, some reference to
time over checkpoints, is important.
If we are flying with older instrumentation and maps, doing so is obvious and
necessary, but why with EFIS? Again, if the electronics have a problem, we know
how far along we are and where to start looking if we’re back to the basics. A lot
of this theory is based on redundancy of aircraft. Admittedly, some of the higherend equipment is so redundant it’s right up there with high-end turbine aircraft,
and it’s hard to imagine total failure with nothing from which we can navigate.
However, in the airline, on those highly redundant airplanes, we still kept a “howgoes-it” log, at the side of the flight plan, comparing each checkpoint passed with
estimated time as well as planned fuel versus actual. With all the snazzy electronic
flight-planning systems out there, we can make up some pretty good flight plans,
from which we can easily keep track of time and fuel. Or, if we want to exercise
our neurons, we can get out a whiz wheel and figure one out. Either way, whether
we do this paper and pencil or by following electronically, we need to keep track
of time and fuel and whether we are running over or under our targets.
As to navigation on cross country flights, we always want some basic
reference to course headings, as corrected for the day’s winds aloft. A well
planned flight log, which we update with actual time and heading reference, can
easily present this information. The obvious reason is incase our electronic
navigation has a problem, we have something to work with, especially if IFR
and/or night. Even flying highly redundant jet airliners over the ocean, with
multiple IRU/GPS systems, the flight plan had a little chart that gave checkpoint,
true heading, variation, magnetic heading, and wind correction angle based on
forecast wind. It was rare odds that we’d be down to wet compass and who knows
what, but that’s the way this business is; we plan for the lowest common
denominator from which we can get down safely. We don’t know if anyone has
ever had to use this information, but for kicks you could watch the course and
wind data; it was very accurate. All that aircraft-transmitted weather data helps
provide good wind forecasting. By the way, the gadget used for that is called an
Aircraft Communications Addressing and Reporting System (ACARS).
During all this, of course, we’ve been watching the weather. En route it’s a
clear-cut problem of being, or not being, in an area of instrument flying, with
possible ice or thunderstorms. Turbulence can be mixed with either. Turbulence is
natural around thunderstorms, but if it’s rough in an icing area, the ice will be
forming fast and heavy, with our problem being the need to get an ATC clearance
out of there. Such a situation generally means unstable clouds, and up is often a
good way out. The clouds, probably embedded cumulus in a general overcast, will
occasionally be visible as we bounce in and out of them between layers.
Think Ahead
We’ve talked before of the different weather conditions and how to cope with
them, but here we should talk about what to think about while flying from one
place to another. Of course, we are navigating, listening to the radio, working
ATC, and keeping track of ground speed and fuel usage. We need to know if we’ll
not only make it to where we want to go, but with enough fuel remaining if it
becomes necessary for a diversion to our alternate.
As we do this, our background thinking is doing the important job of keeping
ahead of the airplane. This is a tremendously important part of flying, in or out of
weather, but especially in weather.
What do we mean by keeping ahead? We have the charts for the next leg of the
trip in hand. As we fly toward one VOR or waypoint, we have the new course
well in mind before ever getting to the station. If our route is electronically
displayed, does it go where it’s supposed to and connect to the next waypoint? We
are mentally prepared for a number of courses ahead. We have the terrain and
altitude clearance well in mind, too. No matter if we’re using VOR navigation
with maps or Area Navigation (RNAV) with GPS routing displayed in front of us,
we should be anticipating well ahead of our route and airplane. If we are running
separate fuel tanks, we need to know when the one we are on is due to run out.
This means we’ll be calculating fuel flow versus tank quantity, then noting the
time of each tank’s depletion, as a reminder so we can switch tanks before the one
in use runs dry.
Other than good basic flying and operation of our aircraft, the most important
task is tracking the weather. We keep up with weather sequences for our route,
destination, and alternate. It takes more than one hour’s weather watching to catch
the trend, seeing if it’s doing what was forecast. If it isn’t, then what does it seem
to be doing? Is it getting worse or better? So we copy weather each hour and
compare it with the last hour. It’s wise, as we fly, to listen in on Flight Watch.
Hearing weather broadcast to others, PIREPs, and requests can give us an idea of
what’s going on with many aspects of the weather. By listening to other pilot
voices, one can pick up a feeling of urgency or tension in the back-and-forth
conversations alluding to the weather turning sour or not acting as forecast. We
can also learn a lot of what’s going on while paying attention to the ATC
frequency we are on, whether we’re on an IFR flight plan or using Flight
Following while VFR. And we can always ask what’s going on ahead of us.
Better weather, of course, isn’t a problem. Worse means we have to plan for
alternate action. What might that be? First, we should check deteriorating weather
against the weather at our alternate. Is the weather holding? Can we feel confident
that it is still a safe place to go, if we cannot get in at our destination? If it is, we
keep going to our destination, make an approach, and if we can’t get in, proceed
to the alternate—just like the book says.
If the alternate is also going down, then we need a new alternate. If our study
of the big picture was complete before takeoff, any change from the forecast
should be understandable. We should be well equipped to take action. A good
weather pilot has this secondary action in mind well before takeoff, action that fits
the day’s weather setup. Again and again, knowing the big picture is imperative!
Being ahead of the airplane means having early plans to handle unexpected
situations. Not being ahead means being the person who faces a changed situation
unprepared, in a panic mode, unsure of what to do next.
What’s It Like?
What’s it like en route, as far as our flying condition is concerned? Well, we are
either on instruments or not. We can be under clouds, on top of clouds, or
between layers. We can be in and out of clouds.
Piston-engine airplanes, especially if they are not turbocharged, will be in
cloud more than any other type, but even so, most “instrument” flights will be
between layers or on top. Clouds rarely stack up from the ground to some great
altitude. When they do, it is in a front or near the low center. These are not far
across, nor do they stay in one condition for long periods.
A big portion of weather flying occurs in postfrontal conditions, and that
means flying on top. Prefrontal conditions will be largely under an overcast that
may gradually squeeze down on us.
What we are saying is that most instrument flight isn’t on instruments. When it
is, it’s because we are flying in a front or low, as we said, or we’ve made a bad
choice of altitude—like being in a stratocu deck when we could be on top of it.
This allows us to sum up and list the conditions. We’ve said we’ll very often
be either on top, under, or between clouds. In these conditions, we are staying out
of ice and are able to see thunderstorms, making it easy to avoid them. When the
clouds get together, we can get ice or fly into a thunderstorm. We are near the
frontal surface. If we aren’t, then we’ve just slipped into clouds that are higher or
lower than the ones we’ve been flying over, under, or between. If we understand
the weather situation, then we should know if it is best to go up or down.
Should the clouds have enveloped us, and we’re near the front, then perhaps
it’s time for ice. This isn’t a reason to feel all is lost. Many times there are abovefreezing temperatures at a lower level. Then it’s simply a matter of getting a
clearance to go lower, remembering terrain clearance.
If the temperature is below freezing all the way to the ground, then the job is
to be certain we are above the lower stratus clouds. This means a higher altitude.
But in getting this higher altitude, we are not trying to get on top; we are just
fishing for an area where there’s little or no cloud; it will probably just be
snowing.
We can pick the altitude above the lower stratus clouds and go into the front
knowing we’ll very likely run into higher cloud, where we’ll get ice. If we do, and
remembering the temperatures are below freezing all the way to the ground, the
only sure way out is turning around, we must not dally in these conditions. Doing
so risks going in so far that we cannot safely turn around and get out.
If we are crossing the frontal surface at right angles, it shouldn’t be too far
through, so let’s be certain we are crossing it the fastest way. If we fly along the
front, then we’ll really ice up.
We have talked about thunderstorms earlier in the book. We recall they are
either air-mass types that allow us to wander around them, or they are frontal, and
we are on instruments, probably near the storms and needing radar. Without radar
or lightning detection, we have no business being in there! If the radar breaks
down once we’re in the weather and playing hide-and-seek with thunderstorms,
we need to be prepared for a rough ride. This points out that we shouldn’t fly
fronts—winter or summer—until we have a lot of instrument experience.
So en route, we watch weather at our destination and alternate, but we also
watch to see if any fronts are getting in the way of our route. Generally,
precipitation and easterly winds make us suspicious of a warm front. Out there
somewhere is the frontal surface, where the winds go from easterly to southwest.
Ahead of that is the large area of precipitation. That’s where the weather is and
where we’ll find embedded thunderstorms in the summer, and sometimes in
winter, too. In the winter, we’ll find snow, and in a more or less narrow band,
we’ll find freezing rain. Until we’re experienced, we simply run away from this
area, either by making an end run, if we have a long flight and this is even
possible, or by landing and waiting it out.
We pick up a cold front more easily, because its wind shift is more dramatic. It
swings from southwest to northwest, with heavy rain, thunderstorms, or heavy
snow and snow showers. It’s rough in summer or winter, with ice in winter,
thunderstorms in summer. Are you equipped to take it on? Equipped in skill and
knowledge and airplane and gadgets? If we have been flying on autopilot, should
it fail in the middle of the front, can we successfully hand-fly through the rest of
the weather? No, not by depending on a ballistic chute, but hand-flying a perfectly
good airplane. If not, we beat a retreat and wait for it to go by.
Flying en route is a crafty time. We watch the weather; how is it doing for our
destination and alternate, as well as developments along the way, deciding if they
mean something different, that something is on the move—again, the big picture.
Watch the ground speed and its relationship to fuel and distance. These, together
and interrelated, are the budget, and we cannot afford to overspend.
Forced Landing with Little Time to See
Suppose we are faced with a forced landing while flying on instruments,
especially if the weather is low, meaning there will not be much time from when
we break out of clouds until we’re on the ground. What then? The first thing is fly
the airplane, then take care of any abnormal or emergency procedures that may
help the situation. Next, we need to consider the terrain under us, and if there are
mountains or ridges, turn so we descend parallel to them and not across. That way
there is a chance of coming down in a valley and at least not banging head-on into
the side of a hill. In about the same time frame as checking electronic terrain
information, if we have a “nearest airport” selection we hit it! If we can make it,
hopefully it has an instrument approach we can easily access. As mentioned
before, we do need to be careful in just heading to the nearest airport, as this may
take us back across the mountains instead of paralleling; it’s better to ding the
airplane in a field than destroy it and us against a mountain. But again, we want to
fly the airplane first, before fiddling with buttons or getting mesmerized with
electronic displays.
With the airplane under control and aimed for somewhere hopeful, let’s call
ATC, declare an emergency, and if we don’t know, ask them about the nearest
airport, if it has an instrument approach, and about the terrain as well. If we have
electronic flight instruments with terrain display, and maybe synthetic or
enhanced vision on the PFD, or even some personal smart devices, (if their use
doesn’t cause too much fiddling versus flying), we’ll have fair idea where we are
headed. No, it is not legal terrain-following data, but if we have no choice because
of an engine failure, it’s a time for the better choice of uncertainty. If we are flying
without technically advanced electronics with all the information talked about
above, and have backed up our airway maps with sectionals, we’ll have an idea
where things are, possibly even an airport. If we’re on top of things, we’ll have a
navigational aid or airport in mind that can help us out.
On top of clouds, one often can see a wavelike pattern in the clouds below. If
so, we descend in the low part, the trough of the wave, and we will possibly be
over a valley.
As the time nears when we’ll pop out of the clouds and face our quick landing,
we slow down to a maneuverable, minimum airspeed, but not so slow as to stall
until ready to touch. There are pretty good odds that we’ll see something before
we hit, possibly having a chance to maneuver and pick a softer place. So our
maneuvering speed should allow us to make some last-minute steeper turns
without stalling. If we are going to stack an airplane, it’s best to do it under
control.
Full flaps and gear down. The gear will help the airplane to decelerate as it
tears off, and the flaps, of course, will give the lowest speed. If we are wearing a
shoulder harness and have maybe placed pillows in front of ourselves (if we can
still see and fly) and our passengers, things may not turn out badly at all. The trick
is to hit under control. It all sounds pretty desperate, but it isn’t quite that bad. We
hope it never happens, and it probably never will.
With all the above in mind, now we see the real potential of a ballistic
parachute. Those who have developed and/or used them will know all the factors
better than we do. However, it would seem whether to use it or not will take
consideration of factors such as one’s experience and flying ability, versus what
we know or don’t know about the weather, terrain, damage of our landing versus
the parachutes’, parameters of the chute’s operation, and seemingly most
important, the probability of all factors versus the well-being of those involved. In
such an unavoidable situation with potential dire straits, the ballistic parachute
seems a very appealing option.
All Is Normal and It’s Time to Get There
Of course, en route flying is also handling navigation and ATC. It is also, during
the not-so-busy cruise portion, a chance to plan the arrival, to get out the arrival
airport area charts, study them for routes and holding points, and then program
our electronic flight systems. It’s the time to study the instrument-approach
procedure and firmly fix in our minds the key points of the approach, including
the lowest altitude we’ll go to (minimums) and what the missed-approach
procedure is, if we don’t get it.
19
Landing in Bad Weather
As we approach the destination, weather takes on a more realistic feeling. Ceiling,
visibility, wind, turbulence, and runway conditions become real, because we are
about to cope with them.
First we try to visualize the weather in relation to our descent. Is there ice or
are there thunderstorms? If ice, as we’ve said, the job is to get well prepared (heat,
props clean, etc.) and descend quickly to a landing before too much ice covers the
airplane. With thunderstorms, we have to detour around them.
Now let’s look back at the basic concept of approaches. There are basically
two kinds. One is an approach providing both lateral and vertical guidance, with
the most precise, called “precision approaches,” guiding an aircraft to the center
of a specific runway. With these approaches, when we are on course and reach the
minimum altitude, we either see the runway or not; consequently landing or
making a missed approach. At current, most of these are flown off the ILS and
GPS, with some larger aircraft using Inertial Guidance, augmented with GPS for
higher accuracy.
The other concept offers only lateral guidance towards either the airport or
runway, depending on the design of the approach. They mostly function off
VORs, Localizers, GPS and the few ADFs that are left, as well as Inertial
Guidance. Without vertical guidance these approaches take us to a specific point
at precise altitude, so we must see the runway and/or its environment, and from
there we finagle an appropriate visual descent to landing. Because these
approaches lack vertical guidance, they have higher minimums and are more
demanding to fly. They are referred to as “non-precision approaches.” However,
the name is kind of a misnomer, because all approaches offer some level of
precise navigation. Most important to remember is that all of these approach
types, whether precision or non-precision, should be flown with the same
discipline and respect.
Flying the Approach
We follow approach courses precisely, as prescribed on the approach plate, with
absolutely no fudging. The altitudes on the approach plate are to be complied with
accurately, which without vertical guidance means after we pass the approach’s
final fix, we descend to the minimum altitudes, as referenced to distance along the
course towards the runway. This is measured by either time or distance. Time is
more prevalent with approaches off VORs, Localizers and ADFs, although they
can have distance reference as well. When using times for the approach, they must
reflect our aircraft’s groundspeed . Using distance, instead of time, is much easier,
and usually is the case with the rock-solid GPS approaches that are rapidly
becoming the most popular; and being independent of ground-based electronics,
provides ultimate utility for general aviation.
There are three phases of an instrument approach:
• The all-instrument part.
• The transition period from instruments to visual.
• The visual part.
The instrument part is the easiest. This is a mechanical thing we learned when
earning our instrument rating. But there are a few tricks and points worth talking
over.
First of all, it’s important to get the airplane settled down and ready for the
approach. That means getting all the approach and landing checklist items out of
the way well in advance. We shouldn’t be worrying about changing fuel tanks,
throwing the flaps out, slowing the airplane down, and extending the landing gear,
while trying to center the needles on any approach. That’s a frantic sentence and
so is an instrument approach that we try to fly without planning ahead. We need to
have everything set for landing before the approach is started.
The Instrument Part
The following scenario is written as if we are hand-flying the approach, which we
should be able to do easily and confidently just by using raw data indications.
This is necessary, as mentioned earlier, even if we often use an autopilot for
approaches, because if the autopilot fails at its job we need to take over
immediately. If we are weak at hand-flying, it probably means we have a weak
instrument scan, which makes it hard to follow the autopilot and consequently
we’re unaware of what’s supposed to happen next. Then, if we have to suddenly
take over and hand-fly, we’ll be way behind, which is a very bad predicament. If
we are close to the ground, this rapidly becomes a very serious problem. The most
important part is to keep on top of things at every moment. We are talking again
of scanning and keeping headings where we want them, along with monitoring
altitudes, descent rates, and airspeeds.
Let’s remember the simple method of keeping a heading by watching our bank
on the artificial horizon. If we never let a bank go unnoticed, we will not get far
off the heading. Part of this is promptly changing the heading when it should be
changed. In other words, if you think a heading change is needed, make it now!
The idea is to keep a short rein on the entire process and never let the airplane get
far from the desired path. Scan often and act quickly but, of course, smoothly.
Glideslope on an ILS, a GPS’s glidepath, or altitude change from approach
without vertical guidance is mostly a matter of descent rate. A localizer needle is
not flown; the directional gyro is flown to a heading, and we refer to the localizer
needle, seeing if that heading keeps us on course. In descent, the vertical speed
indicator, hopefully an instantaneous type, is the key. You set up a certain rate of
descent and see how that keeps you on the glideslope. If we go below, the descent
was too fast, and so we get back on the glide path and try a slower rate. We
bracket the glideslope using the vertical speed instrument, just as we bracket the
localizer with the directional gyro.
So the two important instruments are the gyro and the vertical speed: one for
course control and the other for descent. The artificial horizon, showing attitude in
roll or pitch, is the instrument by which we make our heading or vertical speed
change. If a bank occurs, the heading will change, and we stop it or bank to put
our heading where we need it. If the horizon shows our nose down more than it
has been, we bring the nose back where we want it; if we want to go down, we
make a forward movement that shows on the pitch bar of the horizon. We should
know about what pitch attitude and power setting it takes to come down a 3degree ILS, as well as what attitude and power settings are needed for different
descent rates and airspeeds, should we need to fly a stepped-approach without
vertical guidance. All this will vary depending on the wind.
We refer to other instruments, too: airspeed to keep it within bounds and the
altimeter to see how we are doing with our altitude. We often hear arguments
concerning whether we control airspeed with the elevators and rate of climb with
the throttles, or vice versa. Well, when tweaking the little corrections of an
approach, it’s a silly argument, because what we’re managing is energy, and we do
it the best way for the conditions we’re experiencing. If we’re below the glide
path, our natural reaction is to pull back and get up to it. We zoom a little and get
back, but if we’re quite low, and our zoom takes a long time, we will lose energy
and slow down. Any experienced pilot knows this, and when pulling back
automatically puts on some power. If it’s a little pull-up, and there is some extra
speed, not much power is needed—maybe none. If the airplane is slow and quite
low, a lot of power may be added right away, because pilot experience,
subconscious, or whatever, tells the pilot that additional energy is required.
Stopping to think which to do, add power or pull back, just isn’t the way to fly
an airplane. It’s a smooth coordination of whatever it takes to get the job done
under present conditions, and if a pilot doesn’t understand that, a lot of practice
and learning is needed before trying to fly down an ILS, looking for the bottom of
the clouds at 200 feet or less. To do it all, we scan and scan often.
If we are flying a good old VOR or ADF approach, we’ll need to remember
the course needle gets more and more sensitive as we are near the station. Many of
these approaches cross the station, then continue on a course to the missed
approach point, and over the station the course needles briefly flail around in their
sensitivity. As the airplane flies over the station, inexperienced pilots start making
big turns and deviations, chasing the confused course needles, and the approach
turns into a disaster. We don’t have to do this. Instead, as we approach the station,
we should have things pretty well nailed down as to what the drift is and the
required heading. After station passage, just apply that much drift to the next
heading and cool it; wait a moment or two for things to settle down, and then
resume tracking. When we go to the world of GPS, this issue goes away, and
things become less mysterious.
When we fly these approaches not having a glide path, we simply leave one
altitude and go to another, with time or distance-derived fixes telling us when to
do so. The approaches are usually designed so that there is rarely need to dive for
it, but we should get on with the descent. The supposed smooth transition we
make from starting and stopping the descent rate adds a little time and distance,
so we don’t want to dawdle. The vertical speed indicator shows us how fast we’re
descending and gives us a target. Obviously, we don’t want a descent rate so fast
that it will make recovery at the desired altitude difficult; that’s dangerous. What
our descent rate should be depends on a few easy problems of altitude to lose
versus ground speed, giving a minimum rate of descent between the letdown
fixes. This becomes our rate of descent. If it’s a minute between fixes, or from the
final fix to our missed approach point, and we have 500 feet to lose, a 500-footper-minute rate of descent is the theoretical answer. But because we don’t really
know our exact groundspeed—unless we have GPS—we should add a little. For
that 500-foot-per-minute descent rate, we should probably use about 700 fpm,
making sure we’ll get down in time. If we come up with one power-pitch setup
giving us no more than 1,000 fpm, it will usually fit most approaches and keep
things simpler.
Our rate of descent during these approaches is also a guide for leveling off at
the desired altitude. If the rate of descent is high, then we begin to level off farther
above the altitude than we would with a low descent rate. We don’t want to go
below our target altitude! Be positive when leveling off and don’t delay. Smoothly
but concisely pull the nose up and get it done. A little practice in hitting altitudes
from various descent rates will soon let us know what is needed. It’s good stuff to
know before we start making approaches.
The problem with stepped approaches, which we often call “dive-and-drive,”
is they are not as safe as those with a glide path. If we plan to fly dive-and-drive
approaches, we need to stay sharp and practice them. Fortunately, this is taking a
marvelous change for the better, with GPS allowing glide paths to be created for
so many approaches. Unless we are really sharp with stepped approaches, we
probably should set higher personal minimums or stay away altogether.
When we fly an ILS approach, the closer we get to the missed-approach point,
the more sensitive it gets, even more so than for the VOR approach mentioned
earlier. Consequently, we want to get it tied down as far out as possible to reduce
the need for excessive maneuvering closer in. An ILS approach is a little like a
funnel. Well away from the runway, both the localizer and glideslope are wide,
and as we get close in, they become narrower. This creates a tendency for us to be
a little less precise near the outer marker, and then as we get in closer to the
runway, if we don’t have our headings and sink rates organized, we begin chasing
the localizer and glideslope indicators. The way to make a good approach is to get
on course and stay there as soon as possible. A good portion of missed approaches
don’t happen in the last part of the approach, although it looks that way; the miss
probably started way back at the beginning of the approach, when the pilot didn’t
get on track right away.
The wind will change as we descend, and this will affect our drift and descent
rate. We will have to change headings and descent rates to keep up with it, but the
earlier we have these things under control, the easier it will be to pick up a
change. And remember, the descent rate to stay on the glideslope is a clue to shear.
One winter evening, an interesting event happened in Montreal. A cold front’s
blast of chilly air and shifting wind lay between the airport and the beginning of
our ILS approach. Checking weather just to the west showed northwest winds and
snow. Their ATIS still was southwest and a little drizzle, but the report was nearly
an hour old. Starting the approach to the southwest runway, it was smooth, light
rain and the wind pretty much straight on our nose. Suspicious, we asked the
tower for a weather update—gusty northwest wind with so-so visibility from
snow. A few miles from minimums and just under 1,000 feet above the ground, it
got pretty choppy, and the localizer needle quickly started to drive right. The
weather update had our triggers cocked—quick 30-degree right turn, then
immediately back left, settling on a good right crab. Kind of an airborne hula
dance. It worked, and we broke out about 400 feet, snow blasting across the
runway. That warm room at the Chateau Champlain hotel was very welcome.
What we are trying to do all down the approach is to keep the changes as small
as possible, but always within the limits of what’s comfortable between pilot and
airplane. Close in, the ILS is narrow and the VOR station is small, so at those
approaches’ ends, corrections need to be pretty small as well. It’s the time and
place for maximum concentration.
Close in, Things Get Tight
There’s a lot of pressure when we get in close on the approach; everything
becomes tighter and tighter, and we must watch each instrument intensely,
scanning the important ones frequently. This is the place where hands get sweaty.
It’s the place, too, where the pilot has to be relaxed but alert. We must feel like a
good athlete, intense in concentration but smooth in coordination and relaxed
enough that we move freely. This comes by practicing, by getting the approach
under control early, and by talking oneself into the right mental attitude. When we
get this ironed out, a good instrument approach is satisfying and frankly fun to fly.
Stick with It
As we anticipate breaking out and seeing the ground, we should remember one of
the most important parts of an instrument approach: stay with it!
All approaches are not to the minimum altitude before seeing the ground, and
actually most are not. The ground comes into view in various ways: through
breaks in clouds, or a clean break out of cloud but into poor visibility, perhaps
straight down in snow. We often see the ground before we have sufficient
visibility to see the airport or runway.
Seeing the ground—good old Mother Earth—whom we may not have seen for
hours, doesn’t mean the approach is finished. It isn’t finished until we land and
turn off the runway.
Inexperienced pilots may attempt to continue the approach visually, thinking
they know where they are, but with poor visibility and the field not yet in sight,
things look different. Even an approach at an airport we know well will suddenly
be as foreign as the moon when the visibility is only straight down. About then,
the ground may disappear and that’s a profound shock!
During ground contact navigation, the pilot probably has wandered from the
approach course, but now, with visual references suddenly gone, there’s a wild
attempt to get back on course, but it’s too late, and the approach is missed.
When a pilot leaves the approach guidance and begins to navigate visually, the
tendency is to begin a sneaky descent. It’s a natural reaction to get lower and have
a better look, or it’s done because one isn’t scanning back to the instruments
enough to check that altitude and airspeed are in safe territory. This pilot has
entered a very dangerous domain!
The altitudes for an instrument approach are set up to clear all obstructions
along the approach path. It is best, by far, to follow these altitudes precisely and
not be “suckered” into letting down below them because one can see the ground
and gets the false impression that this makes everything okay.
If there is enough ceiling, the approach altitude will put us in the best position
to land. This descent to landing should be, if at all possible, about a three-degree
glideslope, which is the same as an ILS. Visual glideslope reference is about the
same. A fair wag for this is 300 feet per mile. If there isn’t enough ceiling and
visibility, you shouldn’t be landing anyway. Why deviate from the procedure?
There isn’t any good reason, so don’t. We cannot stress this enough. Whatever the
approach, it is designed to lead us to the runway at the proper altitude, so why
deviate from it? No, hang right with it until landing is assured.
All this is especially important at night, even in fairly good visibility. The lack
of a good solid reference can cause sensory illusions that will lead a pilot into the
ground when thinking all is well. A few lights or, in daytime, a dimly seen
building or tree clump, combined with a wing being down and off-level nose
position, can easily give the illusion that one is higher than appears. Lots of
airplanes have piled up because of this.
When the runway or approach zone slopes up, we think we’re higher than we
really are. When runway lighting is set to an intensity lower than normal, we seem
higher as well. Snow cover does the same thing, as do conditions of haze, smoke,
and darkness; all of this makes us seem higher. These sorts of illusions have
caused accidents. The answer is to trust instruments, not what we think we see.
Stay with the instrument approach procedure until the runway is in view and it’s
definite that we “have it made.”
It is the dangerous place, when one casts aside instrument reference and uses
only one’s eyes for guidance. Again, and again, we must not descend below the
final altitude until the runway is well in view. What we can do is adjust our
descent by reference to the runway, using our instruments to maintain proper
attitudes and power settings for normal sink rates until we’re certain of our
landing. Even at the point where we cross the runway’s end, we should be
checking instruments—airspeed and especially altitude. With the runway in view,
it is still possible to get too low, because our eyes play tricks; a look at the
altimeter will sometimes be startling! But if one has taken frequent, quick looks at
the altimeter during descent, even though “contact” with the ground, these
surprises will not happen.
During an ILS approach, keep in mind how much crab angle has been
necessary to stay on course. Let’s say the ILS course is 50 degrees and it has taken
about 60 degrees to stay on the localizer. This means that when we break out and
see the runway, we’ll have a 10-degree crab angle. The runway will come into
view favoring the left side of the windshield. The instinctive reaction is to kick
out this crab and line up with the runway. We shouldn’t do this, because the
airplane will then drift off the centerline, and it’s surprising how fast this happens.
If the ceiling is low, we’ll probably not have time enough to maneuver around and
get back on the runway before we reach it. Don’t attempt to get lined up with the
runway once off to its side by any appreciable amount. It’s a case of, “You can’t
get there from here.” The geometry and dynamics prohibit wild maneuvers that
will get us back on the runway, unless we need only a small correction. It is time
to swallow pride, pour on the coal, and do a missed approach. It’s a lot better than
hooking a wing or engine pod or maybe crossing the runway to wind up in the
boondocks.
So on the ILS, note the drift and visualize where and at what angle the runway
will come into view. Then, don’t be too quick to kick out the drift. See how you
are doing first. You may have to hold it all the way to the ground.
When We See Again
Now we’ve made an approach with vertical guidance—ILS or otherwise—and
have broken out of the clouds where we should. What happens? Unfortunately,
and just like the approach without a glideslope, there’s a great tendency to push
over and “go” for the runway. They call this the “duck under” maneuver. What it
does is puts one too low, and it’s dangerous.
There’s more than one way to duck under. So-called experts blame pilots for
shoving it over to see the ground. Well, there are probably some cases of that
nature, but I have more faith in pilots’ intelligence and will to live. Another
reason for the duck under, as we’ve said, is flying contact and forgetting to scan
the instruments frequently, because, basically, even though we see the ground, it is
still IFR flying in low visibility.
There is another reason for getting below the glideslope, and that’s shear.
Normally, as we descend to land, the headwind becomes less during the descent.
This causes airspeed loss and the aircraft’s nose therefore lowers, which, if we’re
not right on top of it, will cause us to slide under the glideslope either on
instruments or while trying to maintain visual contact. It’s one of the main reasons
we’re startled to see an altitude loss when we look back at the altimeter. This isn’t
dramatic shear, but simply a few knots of wind reduction during descent. It’s a
subtle thing, but one to watch for. It emphasizes, again, the importance of
scanning those instruments.
To go back a bit, we were on instruments following the glideslope and had
established an appropriate rate of descent. But the moment we look up and see the
approach lights, we lose glideslope information. The approach lights let us see,
but don’t do much for vertical guidance. The glideslope indication is inside on the
instrument panel, not outside where we are looking. Unless there’s a Visual
GlideSlope Indicator (VGSI ), we haven’t any glideslope reference. Looking back
inside at the glideslope indicator doesn’t help, because the glideslope deteriorates
as we get lower.
ILS runways approved to CAT II and III have accurate glideslope indication
almost to the ground, but others are not that precise. Their glideslope accuracy
deteriorates as we approach the ground. How high this happens depends on
various things, but terrain has a lot to do with it. Some glideslopes are good to 50
feet, but I’ve seen others that dip or become erratic as high as 150 feet. So at low
altitudes, if the glideslope isn’t a CAT II or III runway, and the course bar
suddenly makes a fast and pronounced excursion, don’t chase it. Simply hang on
to the rate of descent that’s been taking you successfully down the glideslope;
that’s your new one.
This is a dangerous area. Enough airplanes have landed short under these
conditions to prove the point. The airplane condition at that point aggravates the
situation. It is going slowly. The pilot pushes over. The airplane goes through a
shear zone. It sinks to a dangerous level before the pilot can catch the cue visually,
if ever. That is why it would be nice to have those VGSIs on all instrument
runways, but such is not always the case. There are variations of VGSIs, and one
should study and know them all. Equally important is to study the various lighting
systems for approach, runway end, and runway lights before doing serious
instrument flying and approaches.
In relation to seeing in poor visibility, the availability of synthetic vision and
enhanced vision is rapidly being added to electronic flight instrumentation.
Synthetic vision creates an animated terrain image representative of where we are
flying at any time. This terrain image is referenced from GPS position, and the
wizardry that can relate actual terrain to a GPS position; then displays it as an
animated image for our instrumentation. That image is usually presented on an
aircraft’s primary flight display. Enhanced vision uses Infra-Red technology to see
through night and cloud for an image of what’s out there. This is often displayed
on aircraft MFD screens. Both give a good idea of what’s out the windshield, but
for now, except for some military, government, and select civilian use, it’s
reference-only for our personal aircraft. Again, we should not rely on it for an IFR
approach, but it is a nice reference as we transition from electronic navigation to
visual. Stay tuned; the future moves fast.
Certain airline, military, and higher-end general aviation operations use headsup display, which offers images of basic aircraft parameters and attitude, as well
as electronic guidance, on a see-through display in front of the pilot. It can allow
lower minimums over comparable approaches without it, because of the ability to
observe aircraft and navigation data while also allowing visual contact with where
we are going. Years ago, the French airline Air Inter used it continuously and
successfully with hand-flown, low-visibility landings. I (RNB) flew many
approaches with it in Air Inter’s simulator, with some to zero-zero minimums,
then making go-arounds; it is a beautiful, simple way to fly. Air Inter was a
French airline with a marvelous weather record using the heads-up system.
For now, however, we still have to deal with that transition zone between
leaving electronics for visual guidance, unless we are making an automatic
landing in a high-end operation. In summary, we first remember the rate of
descent you have been carrying on the approach. On breaking out of the clouds,
we take occasional quick looks at the instruments to see that we’re holding nearly
the same rate. If we are, the descent path should be nearly correct, unless there is
bad shear.
An important point when flying an ILS is verifying that the altitude of our
aircraft at the Final Approach Fix (FAF ) is the same as that published on the
approach plate for the FAF. This confirms the correct altimeter setting. If it is off,
we should verify the altimeter setting. If there are any uncertainties, we should
discontinue the approach and get the altimetry organized before starting again. At
minimums, there is not much room between us and the ground, so our altimeter
has to be correct.
What we’ve said in all this is not to trust our eyes for glideslope guidance
when visibility is low, especially at night. This applies to the VFR pilot under
fairly good conditions, too. We’ve also said that an approach doesn’t end just
because we can see the ground. And when we see the ground, we must kill the
desire to push the nose down and duck under!
Autopilots Doing the Work
As we have mentioned before, many aircraft have autopilots that make the
approaches and do it magnificently. As also alluded to before, this doesn’t relieve
the pilot from constantly monitoring how the autopilot is doing. It’s important to
know the heading it’s flying, descent rate, and power in relation to what’s normal
and what it is actually, whether our throttle is manual or automatic. Knowing all
this will be very handy if the autopilot should suddenly disconnect or fail, and this
does happen. And, of course, it’s a check that the autopilot is doing its thing
properly. Careful observation of the approach has the pilot informed and ready to
take over manually, for any reason, with minimum fuss.
Circling to Land
Sometimes an approach is made but the wind is on a different runway, or the
approach itself is designed to put us over the airport instead of lined up with the
runway, and it is necessary to break off and maneuver, to an appropriate runway.
This maneuver is referred to as “circling to land.” It is a dangerous procedure and
requires higher minimums, generally 1,000 feet or more. In rain or snow, with
poor visibility, perhaps at night, this is not easy.
The tendency is to look out at the ground and runways, forgetting the
instruments inside. It is very easy while doing this to have altitude slip away
unnoticed and, with bank giving illusions, get far too low. How to do it? By
instruments! Fly headings and maintain altitude with occasional looks outside to
see how we’re doing until lined up on the heading of the desired runway and we
can see it for landing. It is a watching-in and glancing-out procedure with
constant reference to the necessary instruments. If at all possible, don’t do a
circling approach under poor weather conditions, even though the minimums
might allow us to do so. Also, if we have a choice between a circling approach
and one straight in, take the latter.
To Touch the Ground
So we’ve made a proper approach and now see the runway. What’s next? Actually,
we continue with the descent and approach problem. We cannot get too low until
the runway pavement is under us. While we want to get on the ground, we also
don’t want to cut it so short, leaving the wheels on the last row of approach lights.
It’s one of aviation’s many compromises in that you don’t want to land too long,
with the danger of going through the fence at the other end, and you don’t want to
land too short, either.
This brings up an important point about landing the airplane once the runway
is securely under it. The point is to get it on the ground. This isn’t the time to float
along with a little excess speed trying to gently slide the airplane on the ground
and impress those riding along. Even if the landing is a little rough, get it on the
ground where the wheels and brakes can begin to get it stopped. And in doing
this, we want as much runway ahead as possible, in case we start aquaplaning on
a water-covered surface or sliding on ice.
So there’s a nice, delicate balance required in the approach. It starts with
airspeed before the runway. We need enough to take care of gusts and shear, but
not so much that we come screaming in over the runway, float halfway down it,
and leave valuable runway behind, instead of using it to stop. These are the kinds
of judgments pilots make alone and without help.
Low Visibility
Now a few points about low visibility. It’s interesting to note the following table
of the percent of missed approaches versus visibility, as taken from records at
London airport for three years:
Runway Visual Range (feet)
1,970-2,300
1,620-1,970
1,475
1,312
Missed approaches (%)
22.2%
30.6%
40.5%
45.5%
The above is older information, in an era when most landings were not
automated. However, since most general aviation operations do not go below
Category I minimums, this information still simply says that it is sometimes tough
to make a successful landing when you cannot see. It says there isn’t any point
being a hero, trying to get in under conditions that are just too tough.
These low visibilities are generally there because of fog. During this
condition, the visibility-measuring device may only see a portion of the runway
area, although many runways at larger airports now have RVR measurement in
two and possibly three or four areas along the runway, which give roll-out area
visibility values. However, without RVR, one may roll out into a zero-zero fog
patch. Very low visibilities are touchy and require objective analysis about
whether or not it’s worth trying before doing so.
Ground Fog
There’s another fog condition that deserves attention, and it doesn’t have to do
with an instrument approach. We can fly in clear weather, day or night, and note
that our destination reports zero-zero in ground fog. We get over the field and are
surprised to see the runway and airport below us well in view.
This is simply because we are looking down through a very shallow layer of
fog, rather than through it horizontally. But if we say, “Heck, I can land in that,”
and make an approach, we’ll get an awful shock as we descend and suddenly,
about the time we start to flare the airplane for landing, go on solid instruments.
What then? Pour on the coal and get out. If it’s too late for that, hold a steady
descent rate and attitude until you touch. Then get stopped as fast as possible and
hope you do before running out of runway.
On the Ground
Okay, let’s clean up the last parts of our approach and landing. We’re on the
ground and stopped; is the approach over? No. The next order of business is to
quickly clear the runway. There’s an airplane a couple of miles out about to land,
and the tower cannot clear it until we’re off the runway. So the obvious routine is
land and clear the runway, as soon as possible.
As mentioned in earlier chapter, if we are on an airport with high-speed
turnoffs, sometimes they aren’t as high speed as they sound. If the runway and
taxiway are wet and we start to turn off at fairly high speed, we can be shocked to
find that the nose wheel may have turned toward the taxiway, but the airplane
hasn’t. The nose wheel, without much weight and traction, is just skipping
sideways, while the airplane is going somewhere between the runway and
taxiway, which is in the boondocks! Find the speed at which our airplane can
make that turn on a slick surface, and be there before trying to turn off.
As to slippery, we chatted in the takeoff chapter about wet and dry snow and
slipperiness and its effects on an aborted takeoff. On landing, we obviously have
the biggest stopping concerns. With general aviation aircraft operating from
smaller, and at times less fastidiously preened airports in adverse weather
conditions, it’s worth considering some braking action criteria.
The International Civil Aviation Organization (ICAO) has criteria for this:
• Good braking = Dry snow < ¾ inch, water depth of ≤ ⅛ inch, and compacted
snow with an outside air temperature (OAT) ≤−15 degrees C. (Good is the best
braking criterion.)
• Medium (fair) braking = Dry snow > ¾ inch and compacted snow> −15
degrees C.
• Poor braking = Wet snow, slush, water > ⅛ inch and not melting ice.
• Nil braking = Melting and/or wet ice. (This shuts down a commercial airport,
so one PIREP of nil braking can have interesting results.)
• Unreliable braking =Wet snow, slush, standing water. (A potential legal
quandary for the pilot in command, if they elect to land with this braking
report.)
As explained before, larger airports make braking-action tests, and report that
versus just the coverage of water or frozen precipitation. However, if we’re at an
airport that doesn’t make reports, this gives us a guide of what to expect and plan
our operation accordingly.
When you are operating on a hard-surface runway with a very thin coating of
snow, at just freezing temperatures, it can be pretty much nil braking. Landing one
night at Boston, with the temperature right at freezing −32 degrees F—and a very
thin coat of snow, our brakes did little if anything. With anti-skid, one applies the
brakes and holds them there, which that night resulted in nothing, except the
“thump-thump-thump” of cycling anti-skid. Reversers were used gingerly,
because aft engine jets tend to weathercock on slippery runways with any
crosswind. We were light and landed accordingly, but used about twice the normal
runway: at least 8,000 feet.
As said in previous chapter, another thrill is weather cocking when barreling
down the runway. The deal there is not to try and return to the runway centerline;
instead, just realign with the runway direction. This prevents chasing the
centerline, which risks starting an excursion all over again.
By the way, frost and moisture on a grass runway is like greased lightning,
with almost nil braking.
An Approach Briefing
Before we go to work and fly one of these approaches, we should leave time to
pull the whole arrival and approach into perspective. Just as we homogenize the
takeoff with departure and takeoff briefing, we should have an approach briefing.
Again lengthy at first, but when we do this as a habit, it becomes simpler and
quicker. Below are some suggestions, open for individual preference:
• Weather: Its affect on:
• Descent and arrival
• The approach (visibility, ceiling, winds, what we’ll see at minimums).
• Airport/runway conditions.
• NOTAMS:
• Review them for airport and approach.
• Standard Arrival Procedures:
• Limitations and restrictions.
• Terrain:
• Approaching the area and around the airport.
• Approach Chart Review:
• Approach used (type, limitations)
• Chart date (currency but mostly comparison for two-pilot operation)
• Navigation aid/system used (frequency/identification or programming
verification)
• Approach course (direction, any transition to it and altitude)
• Final Approach Point/Fix (FAP/FAF) height
• Minimums
• Altimeter bugs/reminders
• Missed approach point and procedure
• Minimum sector altitude and navigational aid on which it is based
• Highest obstacles within 50 miles
• Small operational notes scattered around chart (radar required, descent
limitations due to obstacles, etc.).
• Figure any rates of descent and time of segment for non–glide path
approaches.
• Airport:
• Runway, lightning, markings, length, surface, turnoffs, and so on.
• Automation:
• How we will fly the approach; automated or hand-flown?
Lastly, if we are flying a technically advanced aircraft, we need to understand
the system well, and make sure the approach is properly programmed. There are a
couple of thoughts we feel worth mentioning. One is to carefully cross-check that
we have programmed the proper approach; with so many different types,
especially multiple choices to one runway, we can easily mess this up, especially
if we are busy or sidetracked. Second, we need to have all the programming and
related briefing done well before we are in the airport environment, preferably
before the descent.
If we have paper approach charts and other similar stuff, it’s a lot easier if they
are held by a handy clip on the control wheel or instrument panel, so we can see
them easily and without juggling them on our laps. There are nice ones in some
airplanes, as well as ones we can buy. If we’re on the cheap, a good metal clip
with a rubber band on each side hooked over the control wheel horns works well.
With all this done, we are ready for descent and landing.
The Toughest Case
Suppose the worst happened and for some difficult-to-explain reason one got
caught with no alternates, no fuel, and a fog-covered, zero-zero airport as the only
place to go. I (RNB) did this in Alaska on the Aleutian chain during World War II.
It wasn’t zero-zero, but it might as well have been. The ceiling was essentially
zero, and the visibility was about 200 feet in snow and fog. Fortunately, I was
over a good airport, Shemya, which had a long and wide runway.
I came down the ILS (ILSs were new gadgets then) and carefully checked the
descent rate needed to follow the glideslope. I flew the ILS as tight as possible.
When we were under 200 feet and the glideslope started to wiggle and deteriorate,
I just held the rate of descent until we touched. Then, control wheel forward (the
B-17 is a tailwheel airplane), I slammed on the brakes and tried to stay on the
localizer and get stopped before hitting something. We made it. Incidentally, I
made a few practice approaches and go-arounds to get an idea of drift and descent
rates before doing the one for keeps.
What really impresses you is that with near zero visibility, you really don’t
see! A few fuzzy lights aren’t enough for guidance, and you are helpless and feel
helpless. This feeling can occur with visibilities up to 1,000 feet or so, depending
on how fast you land. It’s an excellent lesson to make one realize that there are
human limits, and we shouldn’t try to exceed them. Too many things happen too
fast.
In the airlines, we trained to 300-foot visibility in simulators, but in the real
world rarely saw anything below 600 feet. It’s all done automatically, and your
task is flying through it mentally, hand on wheel and throttles, waiting for
something to go wrong; if rarely it ever does, but by nature of the business, we
have to be prepared. The more interesting of automatic approaches were Cat II to
100 feet and 1,200-foot visibility, where you disconnected the autopilot and
landed manually. That was the 727 world, which we mentioned earlier in the
book, but at 100 feet and a third of a mile it was basically a trajectory to the
runway, including superb in-runway lighting. Arguably a general aviation ILS to a
200-foot ceiling and 1,800-foot visibility, flying about 80 knots, is a more
demanding task. That gives us around half a minute to the runway, which is plenty
of time to break up a stabilized approach, if not disciplined with sink rate and drift
correction. This returns to that concept of still referencing the attitude indicator,
while also having visual contact with the runway environment. If we can fly the
approach automatically, especially when the weather is at minimums, it is the best
way to go. It allows us time to constantly check all phases of the approach, while
computers and servos do the manual labor. However, when the approach is flown
with the autopilot, by the time we reach minimums it is necessary to disconnect
the autopilot, and immediately be capable of competent hand-flying.
Without this capability of flying a coupled approach with the autopilot, a pilot
flying very low approaches by hand, especially a single pilot, will be
concentrating so hard on flying that there will be little if any time to check other
important things. With the constant scanning of all parameters for the basic flying
of the approach, it is hard to focus on peripheral aspects, such as looking for
ground contact, airport environment indications, focusing on radio transmissions,
and transitioning to the ground contact scenario. It is hard to do, unless we are
really current, on our game, and overall a very capable pilot. One reason really
good pilots are quite capable is because they know when to admit something
cannot be done to its best performance or safely, and accept limitations based
upon this modest judgment.
When we fly non-precision approaches, the world gets more difficult and
inconsistent, because these approaches do not bring us as close to the runway, as
does an approach with vertical guidance. There, we have to be even more
disciplined. If, however, we take some lead from automatic approaches, where the
autopilot takes the aircraft right down to landing, we find that accidents don’t
seem to happen. This seems to prove the point that if folks stay with the approach
right to the runway and overcome that desire to finish it by just eyeball, rather
than staying with instrument reference, there will be a lot fewer accidents.
20
Teaching Yourself to Fly Weather
With the idea that one crawls before walking, we can teach ourselves to fly
weather. It’s a progressive, self-taught process that uses our own program and we
set the challenges and pace.
In the work of getting an instrument rating, we made practice IFR crosscountry flights, getting clearances, working the radios, managing navigation,
gathering weather, and all the rest, even though we weren’t flying actual bad
weather. Now it’s time to start our “home study” weather program.
Each day, in our advancing times, the complexities of air traffic control,
navigation, and communications grow, so that all the experience we can get in this
area is important. If, on each flight, VFR or IFR, we are on a flight plan and doing
all the work required, we will become facile with this part of the job and do it
smoothly, almost automatically. Once this has become an easy task, we will have
time to think about the weather.
Where’s the Emphasis?
The balance in flying between ATC and its communications, versus the actual
weather, has tipped toward ATC as a major challenge. Weather accidents can
occur when pilots become so engrossed with an ATC altitude or route clearance
that they get into trouble with ice or thunderstorms because their attention wasn’t
on the weather as the primary problem. Pilots, especially new ones, tend to be
more afraid of authority than of weather.
This, of course, is illogical and perilous. If the route or altitude assigned
doesn’t fit, it’s time to tell ATC that you want something different. If we are
battling a difficult situation and ATC keeps pressing us with complex routings or
unworkable requests, we should be prepared to tell them that we have urgent
weather problems and need help, not hindrance. They will help if at all possible.
All this comes more easily if we are prepared by being able to handle the ATC
complexities, having a well-organized cockpit, knowing our aircraft and its
systems, understanding the regulations, and having concise communications with
headset and boom mic, not fiddling with a hand microphone. We need that hand
for tuning and programming today’s avionics systems, with the other either flying
or ready to, if we’re depending on autopilot. It is sometimes a challenge to find
realistic weather when we’re either learning to fly or practicing, but ATC is
always there as the real deal, not knowing whether we’re practicing or not. We
should practice as much as possible.
Learning the Weather
Now let’s get on with learning to fly weather. The actual weather part we sneak up
on by flying a little at first, more as we gain experience.
Let’s take a look at a step-by-step method. These steps are flexible guides, and
one’s own judgment will vary them as our ability grows along with our degree of
comfort in the different stages of weather.
The idea is to fly weather with safeguards that relate to our experience. After
we feel comfortable flying weather conditions of the first step, we take on a little
more in step two, and so on. The steps are:
1.
2.
3.
4.
5.
Fly good weather to good weather on top.
Bad to good.
Good to bad.
Bad en route.
Thunderstorms.
Now, let’s talk about them.
Step One
The first step, good to good , means we leave a point that has broken clouds or
better and fly toward a point that has the same conditions and is forecast to remain
that way or improve. The ceilings should be 2,000 feet or higher, the tops 7,000
feet or lower. No fronts should be moving toward the destination. Temperatures
should be above freezing, and there should be no thunderstorms.
This flight will mean climbing up through clouds for an on-top flight and
descending through them at our destination. It will require watching weather to be
certain things stay as we want them, and, of course, a flight plan and working the
ATC system.
This condition will generally be found in the stratocu cloud decks behind
passage of a low pressure or front. It gives an opportunity to take on more or less
weather, depending how close behind the low, or front, we take off.
At first we might wait a day after the low passage for the stratocu deck to
become thinner. Later, as we gain experience, we can take off closer and closer to
the departing weather, until we are taking off with a ceiling that’s quite low,
climbing to a top that’s quite high, or flying on instruments to a destination that’s
overcast.
Step Two
This leads into step two, bad to good. It’s simply a continuation of the first step,
but departing closer to the low and front until we are taking off just after its
passage. We should be careful not to take off before the front has passed or while
it’s passing, because that can be a very demanding experience.
The key thing in both these steps is that we are always flying toward good
weather. We want to be certain it’s forecast to stay that way, too—no fronts
moving in, as there might be if one took off from an airport that just had a warm
front passage with weather improvement and then flew across the warm sector of
the low to come upon a cold front. In this case, one should realize that out west
somewhere there’s bound to be a cold front coming along that we don’t want to
get involved with. When starting these first steps, it’s best to take off after a cold
front has passed. Then there should not be any more fronts for quite a long
distance.
There are special situations, like the Los Angeles basin, that are excellent for
bad-to-good flight experience. The frequent low stratus allow for an instrument
departure and a climb to on top, where it’s CAVU, and then a flight to someplace
in the desert, like Palmdale, where the weather is good. This generally can be
done without running into the problem of fronts.
We can back up and start these two steps over, but with some ice. The first
sight of a smear of ice across the windshield is quite interesting if there’s a way
out nearby. We can do this by climbing through a thin, below-freezing stratocu
deck, 4,000 or 5,000 feet thick that has a good base, 2,000 feet or better, at both
departure and destination. As we get more accustomed to ice, we can take this
deck a little thicker and a little lower. (The airplane should be certificated for
flight into known icing conditions, which admittedly is hard to find with most
light general aviation aircraft.)
Another good method of learning about ice is to fly in a stratocu deck that has
ice, as well as in a freezing level at some safe altitude below, so one has the
chance to descend below the clouds and melt any ice. This means the freezing
level should be at least 2,000 feet or so above the highest terrain. This condition is
often possible in the spring and fall.
Step Three
Step three is good to bad . This means to fly toward a destination that has weather
approaching. The departure should have solidly good weather. Doing this, we can
go to an area of low ceilings, shoot a low approach, and if there’s trouble, turn
around and go back to where it’s good.
We should plan, at first, on getting to the destination well ahead of any
difficult weather, but be prepared for surprises. It may move faster than expected.
This way, you’ll learn how foolish it is to fly to a destination that calls for
deteriorating weather without having a safe place to run.
As experience is gained in this step, one can fly to destinations with worse
and worse weather. The key is to have that out—that safe place to run—which in
this case is good weather behind us. This step should be tackled first without any
ice, and then we gradually work into ice as we’ve done in the previous steps.
Step Four
Step four is bad en route . This means we’ll take on a situation that has a good
destination but something in between that is tougher than just a stratocu deck. It
will be some kind of front.
To start this, we should be without ice and thunderstorms, just as we begin
each step. The destination should be forecast good and to stay that way or
improve. Any front should be well past the destination before we take off. The
takeoff point should be 1,000 feet or better and forecast to stay that way for at
least two hours after takeoff.
We progress in this step by taking off with the weather closer to our departure
point. This requires thinking about a takeoff alternate—where to go if you must
return and the takeoff airport has gone below limits.
We develop this step until we are taking off with bad weather, flying through it
en route, and landing at a point that has recently cleared. At this point, you have
reached a pretty sophisticated level in weather piloting. But there still remain
thunderstorms.
Step Five
To begin thunderstorms , we should fly with only air-mass types en route. They
should be forecast as scattered, so we can wander around them and look them
over from a safe vantage point. There shouldn’t be any fronts forecast within 500
miles of our route or destination. We should have lots of fuel. The destination may
be covered by a heavy shower when we get there, and we want enough fuel to
wait it out or go on to a thunderstorm-free destination. We want to arrive at the
destination with lots of daylight remaining, three or four hours. Don’t go on
instruments with thunderstorms in the vicinity. Don’t try to top them. Don’t cut
too close between two of them. Don’t fly under the anvil overhang.
The progression of learning weather around thunderstorms is difficult, because
any thunderstorms beyond air-mass types will be frontal, and that may mean
flying into instrument conditions while being unable to see any thunderstorms.
Don’t do this without airborne radar and knowledge of how to use it.
We could fly under high-level warm front thunderstorms as a progressive step,
but this is flirting with heavy rain and low stratus clouds, which again means
instrument flight. After air-mass thunderstorms, therefore, the next step is a big
one, that of flying through fronts. As said before, even using radar and lightning
detection equipment, it isn’t 100 percent guaranteed we’ll miss everything, so one
may be forced to fly through a thunderstorm.
Flying amongst thunderstorms in fronts and lows is the big time, and
unfortunately has to be learned the same way we sometimes do in swimming, by
diving in over our heads. A person should at least know how to fly turbulence
before dealing with fronts. Again, if in amongst thunderstorms, airborne radar, as
always, is a must. And this, again, isn’t to help you fly through thunderstorms but
is just an extension of your tools for keeping out of them. Lightning detection
equipment and NEXRAD systems will be a big aid in avoiding thunderstorms in
what we might call a “wide” sense. What we’re saying is don’t go into a heavy
thunderstorm area, on instruments, counting on lightning detection and NEXRAD
to help us weave through as we would with airborne radar.
The learning steps outlined are not hard-and-fast rules. They are guides to
start from and think about. But there are a few firm points that should be rules.
1. Always have an out. Fly toward good weather or from good weather that you
can return to.
2. Take on ice only after other experience has been gained.
3. Don’t fool with thunderstorms for a long time.
4. Don’t get on instruments near thunderstorms without airborne radar or at least
a preview with lightning detection and/or NEXRAD, so we can avoid the area.
5. Have lots of fuel.
6. Have lots of daylight remaining after the ETA.
There are other rules, and they are in the book in many places, but if we
summed up one weather rule it would always be: Have an out! And know the big
picture!
Looking back over these steps, we can see that weather flying experience isn’t
gained quickly. We need several seasons, years, to see the things we should see,
and experience the things we should experience. We must face the facts of
weather flying. A total ability cannot be loaded into us as we would a computer or
by reading a book, nor is it learned quickly. We must remain humble for a long
time—for that matter all of our flying lives—and know when to quit or when not
to go. An instrument rating is a beginning, not an endorsement that one can fly off
into any kind of weather.
During the learning of weather flying, we should be careful about reverting to
VFR flying, instead of remaining IFR. If the weather remains bad, we are again
back to flying down low and trying to weave in and out of mountains or even
over flat terrain with minimum visibility, which is a sure way to trouble.
Remember, VFR in marginal weather is the most dangerous way to fly!
21
Something on Judgment
It is important to realize that in weather judgment, more determination is required
to sit and wait than to fly. The press of wanting to get somewhere will
overshadow the gumption it takes to drag the luggage back to town, miss a trip we
really want to make, or delay getting home. Sadly, these reasons, and more like
them, have caused many accidents.
In judging weather before takeoff, then skillfully assessing and flying it once
airborne, our attention and action should not be influenced by other factors, unless
they become a part of the judgment, such as a mechanical problem that requires
an immediate landing.
As said before, it is not necessary to remain riveted to the idea that we must
land at the airport of desired destination. There shouldn’t be a fixation on that.
Weather changes and conditions may well make it prudent to go elsewhere, with
personal and emotional influences not preventing us from tossing the desired
destination aside in favor of a good, safe one.
Limitations
The technical world of our day has put a lot of impressive equipment in airplanes
to combat weather and make flying tempestuous stuff easier. We see the electronic
flight instruments and autopilots that precisely fly programmed routes from nearly
start to finish, at the same time offering warning and protection against pilots
losing control of their aircraft. Electronic instruments that think for us, giving
computerized cues for flying all phases of flight, including the toughest
instrument approach. There are displays and warnings of obstacles in our flight
path or being too low to the ground. We see artificially rendered terrain from
accurate GPS location, thunderstorm information on the smallest electronic
device, and airborne weather data that constantly updates. These systems offer
greatly improved redundancy and reliability from the era of spinning gyros and
mechanical interfaces. Approved deicing and anti-icing systems tempt us into the
mysterious world of flying ice, then on landing, we have anti-skid brakes and
reverse thrust on turbine aircraft. There are even a few aircraft offering ballistic
parachutes that bring down a whole airplane. There is more coming, and with it a
challenge toward defining what levels of basic ability and knowledge future pilots
will need to be called qualified.
But first, let us clearly and forcefully remember that all this equipment will
not fly all the weather. Mother Nature will periodically dish out weather that we
simply cannot manage.
We’ve gained much—the ability to land with little or no visibility if the airport
and airplane are equipped. We can top much of the weather we once bounced in
and worried about. There’s a long list, but no matter how superbly equipped an
aircraft is, the inside of a thunderstorm is still harrowing, and severe shear on
landing, instruments or no, can do the airplane in. Running low on fuel can
menace flight. Landing in a hurricane can, too. Periodically, we are presented with
weather of a most savage kind, and saying we’ve reached the age of “all-weather
flying” is akin to the folks who said the Titanic was “unsinkable.”
With our equipment has come the need for pilots to use it properly. We must
program computers with the correct data. Keep close watch that all is working as
desired and the aircraft is headed in the right direction, high enough to miss all
terrain and avoid undesirable weather. This doesn’t come easily, because the
sleekness of the airplane and its near perfection lull one into feeling that nothing
can be wrong. Here’s where that overused but potent word, complacency, reaches
its peak. The fact is that our modern aircraft demand more attention, not less, plus
plenty of that old-time pilot’s belief that things can and will go wrong and you’d
better have a skeptical eye roving the cockpit, and weather, on a regular basis. The
equipment and smoothness of aircraft, the quiet shirtsleeve environment, and
digital readouts flicking away easily give a false sense of security, which tends to
overlook the basics. How very treacherous this false sense of security can be!
This automation and potential false security makes it easy for pilots to either
lose previously well-honed basic flying ability, and the thinking that goes with it,
or, as new pilots, never be equipped with these basics in the first place, being
taught to fly solely in conjunction with automated aircraft. As said before, there
will be a day and time when we’ll have to fly and think with the raw basics, with
no automation to help us. The reasons may be a blatantly obvious system failure,
or even more insidious, a simple little issue that may lure us into staring at
warnings or fiddling with buttons, ignoring basic flying indication and sense,
while at the same time not realizing we’re headed for the ground. There is a
chance it may also be dark, turbulent, of poor visibility but if we have learned the
disciplines of knowing when to stop fiddling and successfully fly the aircraft,
even from the raw basics, we can meet most tricks the new age throws at us. But
without such skills, how treacherous this false sense of security can be!
All this has sounded like talk of modern airline and corporate aircraft, leaving
light aircraft out of the picture. With an up-to-date technically advanced general
aviation aircraft, as far as instrumentation and “avigation” are concerned, the
operation and discipline is little different than airline or corporate operations.
However, there is still another false sense—that of what the airplane can do. It
would be wise to remember that while well equipped, the airplane isn’t always of
turboprop or jet performance. These turbine aircraft have real benefits, not the
least of which is zooming through ice and turbulence or other situations in a flash
of high-performance ability—but again, as we well know, even they have their
limits. Up until the recent past, the personal general aviation pilot had far less
opportunity and mentorship to be as consistently well trained, current, and well
equipped as professional flight crew members. Today we have more opportunity
for this than ever before, which is a very good thing.
We have also been affected by the complexity of the ATC system and the
bureaucratic stifling of aviation that has required and produced training of a rote
nature that misses out on judgment. We all wish there was a way to teach
judgment, but it is difficult. Some people seem to have it naturally—horse sense
—and a feeling for weather that intuitively tells them, “it just ain’t smart to go.”
Others develop judgment by accumulating flying experience known as “fright
time.”
In flight, weather often takes a backseat to the system, the system being ATC,
with the pressure of fast talk, keep ’em moving, land one right close after another,
and don’t miss any instructions or make errors. With this comes the frustration of
delays, holdings, long vectors, and reroutes. For the most part, this is not the fault
of ATC controllers, but instead we are all stuck with the same challenges of the
ATC system’s design and concept. Hopefully, the planned future improvements,
designed to orchestrate through automation, will come forth and do their magic.
In the area where most accidents occur, approach and landing, when operating
at busier airports, there’s an element of being too engrossed in the fact that one
airplane is landing right after another. We’re part of that and don’t want to
interrupt it, so we continue our approach, sort of mesmerized by the idea of
landing, without really thinking about weather. The pilot ahead landed or
departed, why shouldn’t I? It’s a form of competition, too. We may not be willing
to be the oddball, the one who couldn’t make it and had to pull out, disrupting
everything. Unfortunately, it takes courage to break out of the “norm,” to say
there’s a thunderstorm too close and I’m going elsewhere, or the crosswinds are
too strong and I want a different runway. But we must remember that weather is
the first priority—not ATC, not the airplane ahead or the airplane behind, or the
fact that ATC may send us off to Lord knows where if we want to stray from the
routine f low. But the law of preservation and the rule of safety first must be the
way. Despite all our modern equipment, weather will, from time to time, humble
the structure of aviation. The pilot’s task is to be aware of these times, be
responsive to them and have enough grit to take action. This applies whether the
pilot has 30,000 hours or 10.
We have all heard the talk of our world’s weather becoming worse. Some ask
how that will affect aviation. One indication is that we are seeing stronger storms,
both as low pressures and thunderstorms. With this, there have been indications of
larger water droplets, which will affect both rain and icing conditions. Maybe
more changes are out there. However, it would seem still knowing the tried and
true theories of weather, and how it tells us its story, will still allow us to apply it
to our flying, with the same prudent decisions that have worked since flying
began.
I (RNB) was fortunate to fly with pilots who showed me what command
meant. We were flying DC-2s and DC-3s then. On one of my first copilot flights,
the captain was Jim Eischeid, a veteran with a special reputation for being an
excellent weather pilot.
We were going to fly Flight 7 from Newark to Chicago. It was a rotten night,
with Chicago forecast low, ice en route. I stood next to Jim in the dispatch office,
discussing the weather with the meteorologist, somewhat in awe, anxiously
awaiting the flight to see how this man, whom no weather could stop, would
handle it. Imagine my surprise when he turned to the dispatcher and said, “It’s no
good. I cancel!” He knew when not to fly. Jim retired after a long career that went
from open-cockpit mail planes to Connies 1 , and he never scratched one of them.
Now we fly in an era that comes closer to all-weather flying. We can fly more
weather far safer than we did back then and, after all, we want the airplane to
work and deliver people and goods reliably, but we have not truly reached the
stage of total all-weather flight, from general aviation to airline, and we probably
never will. In revising this book into the 5th edition, now 2013, it’s been about 75
years since Jim Eischeid cancelled that flight. Thousands more flights have been
cancelled since then, and despite different combinations of pilots, equipment, and
conditions, the ultimate concept of looking it all over and making that decision
has been the same. There will always be some time when it will be wise for a pilot
to say, “I cancel” or “I’m diverting!” The thing is to know when it’s that time for
each of us, and then have the guts to do it.
1 . Connie is a nickname for the elegant, four engine, Lockheed Constellation,
which represented the peak and end of the piston-engine airline era. The next
step was the jet age, but Jim Eischeid, and many of his mailpilot-era
pioneering compatriots, reached retirement age before the jets came into
service.
Suggested Reading and Websites
Books about Weather
Anderson, Bette Roda. 1975. Weather in the West . Palo Alto, Calif.: American
West Publishing.
Bradbury, Tom. 2004. Meteorology and Flight , 3rd ed. London: A & C Black.
Byers, Horace Robert. 1937. Synoptic and Aeronautical Meteorology. New York:
McGraw-Hill.
Dunlop, Storm, and Francis Wilson. 1987. Weather and Forecasting . New York:
Collier/Macmillan.
Edinger, James G. 1967. Watching for the Wind . New York: Doubleday.
Federal Aviation Administration (FAA) and National Oceanic and Atmospheric
Administration (NOAA). 1975. Aviation Weather, AC 00-6A , rev. ed.
Washington, D.C.: United States Government Printing Office.
Lester, Peter F. 1994. Turbulence: A New Perspective for Pilots. Englewood,
Colo.: Jeppesen.
Lester, Peter F. 2007. Aviation Weather , 3rd ed. Englewood, Colo.: Jeppesen.
Pagen, Dennis. 1992. Understanding the Sky: A Sport Pilot’s Guide to Flying
Conditions. Spring Mills, Penn.: Sport Aviation Publications.
Petterssen, Severre. 1968. Introduction to Meteorology, 3rd ed. New York:
McGraw-Hill.
Wallington, C. E. 1977. Meteorology for Glider Pilots . London: John Murray.
Whelan, Robert F. 2000. Exploring the Monster: Mountain Waves, the Aerial
Elevator. Niceville, Fla.: Wind Canyon Books.
Williams, Jack. 1997. The Weather Book , 2nd ed. New York: Vintage Books.
Books on Weather Information
Chaston, Peter R. 2002. Weather Maps: How to Read and Interpret All the Basic
Weather Charts , 3rd ed. Kearney, Mo.: Chaston Scientific.
Federal Aviation Administration (FAA) and National Weather Service (NWS).
2010. Aviation Weather Services, AC 00-45G. Washington, D.C.: United
States Government Printing Office.
Books on Flying the Weather
Collins, Richard L. 1999. Flying the Weather Map , 2nd ed. Newcastle, Wash.:
Aviation Supplies and Academics.
Collins, Richard L. 2002. Thunderstorms and Airplanes . Newcastle, Wash.:
Aviation Supplies and Academics.
Federal Aviation Administration (FAA). 2009. Advanced Avionics Handbook,
FAAH-8083-6 . Washington, D.C.: United States Government Printing Office.
Horne, Thomas A. 1999. Flying America’s Weather: A Pilot’s Tour of Our Nation’s
Weather Regions. Newcastle, Wash.: Aviation Supplies and Academics.
Newton, Dennis W. 2002. Severe Weather Flying , 3rd ed. Newcastle, Wash.:
Aviation Supplies and Academics.
Digital Media
Collins, Richard L. 2002. Advanced Weather Flying. Batavia, Ohio: Sporty’s
Academy.
Collins, Richard L. 2008. Flying Weather . Batavia, Ohio: Sporty’s Academy.
Dennstaedt, Scott C. 2012. Best of AvWxWorkshops.com. Chesapeake, Va.:
Chesapeake Aviation Training.
Fovell, Robert G. 2010. Meteorology: An Introduction to the Wonders of the
Weather. Chantilly, Va.: The Teaching Company.
National Aeronautics and Space Administration (NASA)/John H. Glenn Research
Center at Lewis Field. 2005. NASA In-Flight Icing Training for Pilots.
Cleveland, Ohio: NASA.
National Aeronautics and Space Administration (NASA)/John H. Glenn Research
Center at Lewis Field. 2004. Supercooled Large Droplet Icing. Cleveland,
Ohio: NASA.
Web Access
National Weather Service (NWS) Sites
http://www.weather.gov —NWS main website
http://w1.weather.gov/glossary —NWS Glossary
http://www.aviationweather.gov —NWS Aviation Weather Center
http://www.aviationweather.gov/stdbrief —NWS Aviation Weather Center
Standard Briefing Guide and related weather information access.
http://www.aviationweather.gov/adds —NWS Aviation Digital Data Service
(ADDS)
http://www.crh.noaa.gov/dtx/afdterms.php —Terms of the NWS Area Forecast
Discussion
http://www.srh.noaa.gov —NWS Southern Region Headquarters site. Userfriendly map of the United States from which one can access each NWS
office’s dedicated website. Also a source through which to link into the Area
Forecast Discussion (AFD)/Forecast Discussion.
http://www.nws.noaa.gov/view/states.php —NWS source to access weather data
that is state-specific.
http://www.wpc.ncep.noaa.gov —NWS Weather Prediction Center. Part of the
National Centers for Environmental Prediction (NCEP), a primary center for
NWS weather processing. Excellent source of detailed weather maps and data.
http://www.aviationweather.gov/general/pubs/front —NWS AWC publication The
Front . Articles that inform of NWS products, including their operational use
to aviation.
http://www.srh.weather.gov/jetstream/index.htm —NWS AWC Jetstream online
school for weather. Numerous and excellent tutorials covering weather
phenomenon.
National Oceanic and Atmospheric Administration (NOAA) Sites
http://weather.aero —National Center for Atmospheric Research–specific web-site
for ADDS experimental data.
http://www.wrh.noaa.gov/zoa/mwmap3.php?map=usa —Central Weather Service
Unit (CWSU) National Map for Air Traffic Control that allows access to
nationwide METAR, TAF, and further detailed information.
http://www.spc.noaa.gov —Website for the Storm Prediction Center (SPC).
Model Analysis—Including Model Output Statistics (MOS) and Skew-T Data
http://rucsoundings.noaa.gov —Website to access atmospheric soundings/ SkewT data.
http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller —National Center for
Environmental Prediction. Weather model analyses and guidance.
www.nws.noaa.gov/mdl/synop/products.php —Current Model Output Statistics
(MOS) Forecast Products (all MOS products—long range, short range and
graphical), as well as descriptions to read the data.
Federal Aviation Administration (FAA) Sites
http://www.duats.com —FAA-approved weather and flight-planning source.
https://www.duat.com —FAA-approved weather and flight-planning source.
http://www.faa.gov/pilots/safety/media/ga_weather_decision_making.pdf
General Aviation Guide to Weather Decision Making.
—
Other Weather Sources
http://www.radar4pilots.com —Archie Trammell’s airborne weather radar school
and related newsletter.
http://www.rtiradar.com —Radar Training International, which offers customized
airborne weather radar training seminars.
http://weather.unisys.com —Unisys weather service, which offers a plethora of
weather data, including atmospheric modeling forecasts.
http://www.flightplanning.navcanada.ca —Excellent weather data for Canada and
nearby portions of the United States.
http://airfactsjournal.com —An online journal that emulates the unique offerings
of the original Air Facts magazine. The writings provide diverse information,
education, and enjoyment. Through the journal’s philosophy and
encouragement, a great deal of the material is written by the readers, making
Air Facts a journalistic home for the general aviation pilot and participant.
Acronyms and Contractions
A/FD
ACARS
ADAHRS
ADC
ADDS
ADF
ADI
ADS-B
AFD
AFSS
AHRS
AIM
AIRMET
Altocu
AOPA
ARTCC
ASI
ASOS
ATC
ATC
ATIS
AWC
AWOS
C
CAT
CAT I
CAT II
CAT III
CAVU
Cb
CG
Cu
CuNim
CVG
CWSU
Airport/Facility Directory
Aircraft Communication Addressing and Reporting System
Air Data, Attitude and Heading Reference System
Air Data Computer
Aviation Digital Data Service (website for NWS/AWC
weather data)
Automatic Direction Finder
Attitude Direction Indicator (Artificial Horizon or Horizon)
Automatic Dependent Surveillance–Broadcast
Area Forecast Discussion (Forecast Discussion)
Automated Flight Service Station (same as modern FSS)
Attitude and Heading Reference System
Aeronautical Information Manual
Airmen’s Meteorological Information
Altocumulus cloud
Aircraft Owners and Pilots Association
Air Route Traffic Control Center
Airspeed Indicator
Automated Surface Observation System
Air Traffic Control
Air Transport Command (World War II military air
transportation organization)
Automatic Terminal Information Service
Aeronautical Weather Center (aviation division/website for
NWS)
Automated Weather Observation System
Degrees Celsius
Clear Air Turbulence
Category I approach minimums
Category II approach minimums
Category III approach minimums
Ceiling and visibility unlimited
Cumulonimbus cloud
Cloud-to-ground lightning
Cumulus cloud (CU or cu also used)
Cumulonimbus cloud
Cincinnati/Northern Kentucky International Airport
Center Weather Service Unit
DG
DME
DP
DUAT
DUATS
EADI
EFAS
EFD
EFIS
EHSI
ESRL
F
FA
FAA
FAF
FAP
FAR
FBO
FD
FIKI
FMS
FSS
G
GPS
GS
GSD
HF
HIWAS
hPa
HPC
HSI
HUD
HVFR
IAS
IC
ICAO
IFR
in Hg
INS
Directional Gyro
Distance Measuring Equipment
Departure Procedure
Direct User Access Terminal
Direct User Access Terminal Service
Electronic Attitude Direction Indicator
En Route Flight Advisory Service (also known as Flight
Watch)
Electronic Flight Display
Electronic Flight Information System
Electronic Horizontal Situation Indicator
Earth System Research Laboratory
Degrees Fahrenheit
Area Forecast
Federal Aviation Administration
Final Approach Fix
Final Approach Point
Federal Aviation Regulation
Fixed-base operator
Flight Director
Flight Into Known Icing Conditions
Flight Management System
Flight Service Station
“g-force”
Global Positioning System
Glideslope
Gridpoint Statistical Interpolation
High frequency
Hazardous In-Flight Weather Advisory Service
Hectopascals
Hydrometeorological Prediction Center
Horizontal Situation Indicator
Heads-up display
Hazardous Visual Flight Rules (nonofficial term to
emphasize risky state of MVFR)
Indicated airspeed
Intracloud lightning
International Civil Aviation Organization
Instrument Flight Rules (criteria between 1,000 feet ceiling/3
statute miles visibility to LIFR)
Inches of mercury
Inertial Navigation System
IRS
IRU
Inertial Reference System
Inertial Reference Unit
ITCZ
IVSI
JFK
LAMP
LF
LIFR
Intertropical Convergence Zone
Instantaneous Vertical Speed Indicator
John F. Kennedy International Airport
Localized Aviation Model Output Statistics Program
Low frequency
Low Instrument Flight Rules (ceiling less than 500
feet/visibility less than 1 statute mile)
Low-Level Wind Shear Alert System
Lateral Navigation
Line-Orientated Flight Training
Light Sport Aircraft
Millibar (in relation to altimeter settings, same as
hectopascals)
Aviation Routine Weather Report
Multifunction display
Model Output Statistics
Marginal Visual Flight Rules (criteria between ceiling of
1,000 feet and 3 statute miles visibility to VFR minimums)
National Aeronautics and Space Administration
National Center for Environmental Prediction
Nondirectional beacon
Next Generation Air Traffic System
Next Generation Radar (ground-based Doppler radar)
National Oceanic and Atmospheric Administration
Notice to Airmen
National Weather Service
Outside air temperature
VOR (an old term)
A 180° turn
International Scientific and Technical Organization of
Soaring
Precision Approach Path Indicator (type of VGSI)
Planetary Boundary Layer
Primary Flight Display
Pilot Weather Report
Probability (as referenced in written aviation weather
information)
Rawinsonde observation (tracking of radiosonde equipment
on a weather balloon)
Ram Air Temperature
LLWAS
LNAV
LOFT
LSA
Mb
METAR
MFD
MOS
MVFR
NASA
NCEP
NDB
NexGen
NEXRAD
NOAA
NOTAM
NWS
OAT
Omni
180
OSTIV
PAPI
PBL
PFD
PIREP
PROB
RAOB
RAT
RAT
RNAV
RNB
ROB
RPM
RVR
SID
SIGMET
Skew-T log-P
SLD
SPC
SPECI
STAR
Stratocu
T
T&B
TAA
TAF
TAF-TDA
TAS
TCAS
TDWR
TDZL
TEMPO
TKS
TRACON
Trop
TRW
TV
TWA
USAAF
USWB
UTC
VASI
VFR
Ram
Turbine
Area Air
Navigation
Robert N. Buck (Weather Flying’s first author, editions one to
four)
Robert O. Buck (Weather Flying’s second author, fifth
edition)
Revolutions per minute
Runway Visibility Range
Standard Instrument Departure
Significant Meteorological Information
Thermodynamic diagram for weather (atmospheric) analysis
Supercooled Large Droplets
Storm Prediction Center
Aviation Selected Special Weather Report
Standard Terminal Arrival Route
Stratocumulus cloud
Thunderstorm
Turn and Bank Indicator (Turn and Slip)
Technically advanced aircraft
Terminal Aerodrome Forecast
TAF Tactical Decision Aid
True airspeed
Traffic Alert and Collision Avoidance System
Terminal Doppler Weather Radar
Touchdown Zone Lights
Temporary (as referenced in written aviation weather
information)
Tecalemit/Kilfrost/Sheepridge Stokes (last names of
developers for TKS anti-/deicing system)
Terminal Radar Approach Control
Tropopause
Thunderstorm
Television
Trans World Airlines (pre-1946, Transcontinental and
Western Air)
United States Army Air Forces (World War II name, before it
was named U.S. Air Force)
United States Weather Bureau (now known as the National
Weather Service)
Coordinated Universal Time (also known as Z-Time or
“Zulu”)
Visual Approach Slope Indicator (type of VGSI)
Visual Flight Rules
VGSI
VHF
Visual Glideslope Indicators
Very high frequency
VNAV
VOR
VSI
WAAS
WPC
Vertical Navigation
VHF Omni-Directional Radio Range
Vertical Speed Indicator
Wide Area Augmentation System
Weather Prediction Center
Index
A/FD. See Airport/Facility Directory
Abbreviated Briefing
ACARS. See Aircraft Communications Addressing and Reporting System
ADAHRS. See Air Data, Attitude, and Heading Reference System
ADC. See Air Data Computer
ADDS. See Aviation Digital Data Service
ADI. See Artificial Horizon, or Attitude Deviation Indicator
Adiabatic cooling process
Advanced Avionics Handbook (FAA-H-8083–6 )
Advective cooling process
Adverse conditions
Advisory Plotting Chart
Aerodynamic braking, ice and
Aeronautical Information Manual (AIM)
Aeronautical Weather Center (AWC)
AFD. See Area Forecast Discussion
AFSS. See Automated Flight Service Station
AHRS. See Attitude and Heading Reference
System
AIM. See Aeronautical Information Manual
Air:
cooling of
moisture in
mountain wave and
movement visualization
sinking
temperature influencing molecules of
unstable mass of
Air Data, Attitude, and Heading Reference System (ADAHRS)
Air Data Computer (ADC)
Air-mass thunderstorm
cloud base hint for
flying under
occurrence of
Air Route Traffic Control Center (ARTCC)
Air Traffic Control (ATC)
clearance given by
controller’s job at
flight plan deviation and
frequency switch and
help from
ice accumulation advised of
in-house meteorologists at
learning to fly weather and
NEXRAD used by
precipitation levels of
rushed takeoff and
system design of
thunderstorms and
Air Traffic Control-cleared route, distance and
Airborne data link weather
Airborne radar
frozen precipitation and
ground clutter with
limitations of
maintenance of
rain detection and
signal of
on standby
thunderstorm avoidance and
Aircraft Communications Addressing and Reporting System (ACARS)
Airmen’s Meteorological Information (AIRMET)
Airplane:
boots bonded to
cockpit preparation and
deicing of
FIKI certification of
high-altitude turbulence stalling in
lightning strike on
protection of
retrimming of
self-righting tendency of
wind shear and
yaw and banking of
Airplane performance:
at density altitude
ice influencing
range and
in tropopause
vortex influencing
wind influencing
Airport
alternate choice for
identifiers
landing place other than
late weather at
location of
takeoff rushed by
weather at
Airport/Facility Directory (A/FD)
Airspeed
drop in
for forced landing
thunderstorms and
Airway clearance, calling for
Alternate airport
Altimeter
accuracy of
setting of
Altitude:
adjustment of
clearance
density
mountains and
temperature and
turbulence and
world soaring record of
Alto clouds
Antistatic hardware
Approach, missed
in thunderstorms
Approach and landing:
altimeter and airspeed for
autopilot and
in bad weather
braking action reports and
briefing for
circling
clearing runway
lining up for
descent rate and
glide path
glideslope
GPS
ground fog and
groundspeed and
guidance for
gyro
heads-up display for
headwind and
ICAO criteria for
ice and
ILS
instrument
lights for
low visibility and
minimums and
at night
non-precision
runway minimum practices and
sticking with it
during thunderstorm
touch down
vertical guidance for
vertical speed and
visual approach
wind shear and
winds and
Area Forecast (FA)
Area Forecast Discussion (AFD)
ARTCC. See Air Route Traffic Control Center
Artificial Horizon, or Attitude Deviation Indicator (ADI)
ASOS. See Automated Surface Observation System
ATC. See Air Traffic Control
ATIS. See Automatic Terminal Information Service
Attitude and Heading Reference System (AHRS)
Attitude flying
example of
instruments for
Augmented indications, dependence on
Automated Flight Service Station (AFSS)
Automated Surface Observation System (ASOS)
Automated Weather Observing System (AWOS)
Automatic Terminal Information Service (ATIS)
Autopilots:
approaches and landing
checks against
as crutch
departures and
double checking of
dual-axis
failure of
managing of
high-altitude turbulence and
instruments and
overreliance on
programming of
reliance on
requirement of
single-axis
smart
sophistication of
three-axis
thunderstorms and
turbulence and
during VFR
Aviation Digital Data Service (ADDS)
Aviation Routine Weather Report (METAR)
Aviation Safety Briefing (FAA)
Aviation Weather Center (AWC)
Aviation Weather Services AC 00–45G (FAA)
AWC. See Aeronautical Weather Center; Aviation Weather Center
AWOS. See Automated Weather Observing System
Ballistic parachute
Barometric pressure, isobars connecting
Base reflectivity
Basic-T Instrument Display
Bent-back occlusion
Big weather picture
computerized weather and
en route weather and
meteorologist and
from satellite and NEXRAD
Black-bag flight kits
Blind-flying
“Blind or Instrument Flying? ” (Stark)
Blow-off clouds
Bluetooth-transmitted flight planning
Boeing 777 simulator
Boots, pulsating
Bracketing
Braking action reports
Briefing.
for approach and landing
Byer, Horace R.
Canned routes
Carburetor icing
CAT. See Clear Air Turbulence
Category I minimums
Category II minimums
Category III minimums
CAVU. See Ceiling and visibility unlimited
Cb. See Cumulonimbus
Ceiling and visibility unlimited (CAVU)
Ceilings
Cell generation, in thunderstorm
Center Weather Service Unit (CWSU)
Charts and maps
electronic compared to paper
felt marking pens for
paper
presentation of
pressure-level
sectional
special language for
studying of
surface
Checking weather:
before, during, and after flight
self-briefing and
Circling approach
Cirrus clouds
Cities:
terrain influenced by
VFR near
Clear Air Turbulence (CAT)
flying through
forecasting of
isobars and
jet stream and
tropopause and
Clearance. See also Air Traffic Control
altitude
studying of
Cleared for takeoff
Closed zipper
Cloud streets
Clouds. See also Thunderstorms
blow-off
creation of
en route
front characteristics and
lentricular
snow from
stacking of
story told by
tops
types of
weather influenced by
Cockpit:
formulas stored in
glass
good housekeeping of
preparation of
Code language
rough mental picture created by
weather briefing and
Coffin corner
Cold front
flying through
ice and
rules for
thunderstorms along
weather characteristics of
Command bars
Composite reflectivity
Computerized weather
big picture and
from television
websites for
Convective-layer turbulence
Convective SIGMET
Convective weather detection
Convergence, area of
Cooling by radiation
Copilot, necessity of
Coupled-approach
Cowel heat
Cumulonimbus (Cb)
Cumulus clouds
building of
as thunderstorm predictor
turbulence and
Current conditions
CWSU. See Center Weather Service Unit
Data, raw
Data-linked lightning mapping information
Deck, ice
Density, temperature and
Density altitude
Departure and takeoff:
bashfulness and
briefings for
concentration and
equipment and
functional layers of
ice and
instrument flying and
last minute checklist for
minimums and
programming for
radio and
runway surface and
in snow
taxi time
during thunderstorms
turbulence during
visibility and
wind and
Departure Procedures (DP)
Departure to destination, range needed for
Descent:
ground speed and
ice and
turbulence during
Descent rate, for approaching landing
Destination forecast
Dewpoint
DG. See Directional Gyro
Direct User Access Terminal (DUAT)
Direct User Access Terminal Systems (DUATS)
Directional Gyro (DG)
Distance:
ATC-cleared route and
range and
between two points
Divergence
Downdraft
DP. See Departure Procedures
Drift
Dry climate:
precipitation inconsistency and
thunderstorms and
Dry microburst
Dual-axis autopilot
DUAT. See Direct User Access Terminal
DUATS. See Direct User Access Terminal Systems
Duct design
Dust devil
Dutch roll
EADI. See Electronic Attitude Director Indicator
EFAS. See En Route Flight Advisory Service
EFIS. See Electronic Flight Information System
EHSI. See Electronic Horizontal Situation Indicator
Eischeid, Jim
Electrical discharge
on airplane
chances of
emotion and
protective materials against
types of
Electronic Attitude Director Indicator (EADI)
Electronic charts, paper charts compared to
Electronic flight displays, failure of
Electronic Flight Information System (EFIS)
Electronic Horizontal Situation Indicator (EHSI)
Emotions:
control of
electrical discharge and
en route weather and
fright as
irrational optimism and
requesting help and
self-discipline and
during thunderstorms
during VFR
En route:
clouds and
duties during
EFIS systems and
flight log and
forecast
fuel consumption
relaxation in
thinking ahead during
what it is like
En Route Flight Advisory Service (EFAS)
En route weather:
aloft winds and
asking why and if questions for
big picture weather and
clear, good weather and
detour for
deviation of
emotions and
experience and
forecasts and
fronts and
hourly report and
IFR and
meteorologist consulted during
occlusions and zippers and
pilot’s view of
VFR and
weather reports for
Engine failure:
fuel and
ice and
Engine vapor lock
Engines:
backfiring of
temperature and
Enhanced vision
Equipment and instrumentation
approach plates
autopilots and
Basic-T Instrument Display
comparative checks against
complexity of
condition and type of
constantly scanning of
for departure and takeoff
departure procedure for
electronic seduction and
emergency lighted standby
failure of
hazards increased from
housekeeping needed for
layout of
lighting for
limitations of
in location with pilot
minimum needed of
modern technology influencing
for navigation
paper and clipboard needed as
paperwork and gadgets as
pen/pencil holder as
periodic checks for
power for
preparation of
proficiency of
development of
radar and lightning detection systems
reliability of
scanning of
simplicity of
six-pack round dial
Basic-T location of
turn and bank
upgrade of
for wind shear
wires and plug-in attachments for
FA. See Area Forecast
FAA. See Federal Aviation Administration
FAF. See Final Approach Fix
FARs. See Federal Aviation Regulations
FBOs. See Fixed-base operators
Federal Aviation Administration (FAA)
Federal Aviation Regulations (FARs)
Field, as landing place
FIKI. See “Flight Into Known Icing Conditions”
Final Approach Fix (FAF)
Fixed-base operators (FBOs)
Flight Director
checks against
flying through
raw data not matching with
“Flight Into Known Icing Conditions” (FIKI)
Flight log
Flight Management Systems (FMS)
Flight planning:
ATC deviation
Bluetooth-transmitted
self-briefings and
sources of
for VFR
Flight Service Station (FSS)
briefings from
consolidation and centralization of
human communication from
opening remarks to
pilot briefings by
on VFR
Flight Watch (EFAS)
Fluid anti-icing
formula for
precipitation and
success of
types of
FMS. See Flight Management Systems
Fog
ground
turbulence and
of windshield
Forced landing
Forecast
accuracy of
destination
en route weather and
future
during holding
for ice
inaccuracy of
prediction of
testing of
time limits of
of wind shear
The Front
Frankenfield, Jim
Fronts:
cloud characteristics close to
en route weather and
ice and
in Northeast Corner
stalled
surface wind and
thunderstorms and
toughness of
types of
weather along
on weather map
winds and
FSS. See Flight Service Station
Fuel:
airplane capacity and
engine failure and
Fuel consumption:
during climb
en route
headwinds and tailwinds influencing
during holding
planning for
by weather
Fuel reserve
Glass cockpit
Glide path
Glider pilot
Glideslope
Global Positioning System (GPS) navigation
sectional chart compared to
VFR and
Government regulations, on fuel reserve
GPS. See Global Positioning System
Gradient wind, surface wind and
Gress, Charlie
Ground clutter
Ground fog
Groundspeed
Gusty winds
Gyro. See also Directional Gyro
approach and
slaved
Hail
damage from
location criteria on
Hand-flying:
ice and
by pilots
skills for
in turbulence
Hazardous In-Flight Weather Advisory Service (HIWAS)
Hazardous Visual Flight Rules (HVFR)
Haze. See also Pollution
Heads-up display, for approach and landing
Headwinds:
approach and
fuel usage influenced by
hazards of
ridges and
Heavy rain
HF. See High frequency
High-altitude turbulence
airplane stalling in
autopilots and
High frequency (HF)
High pressure areas. See Ridges
Highs
HIWAS. See Hazardous In-Flight Weather Advisory Service
Holding:
range during
unpredictability of
weather forecast and
Horizontal Situation Indicator (HSI)
Hot wings
Hourly reports
HPC. See Hydrometerological Prediction Center
HSI. See Horizontal Situation Indicator
HVFR. See Hazardous Visual Flight Rules
Hydrometerological Prediction Center (HPC)
IAS. See Indicated airspeed
ICAO. See International Civil Aviation Organization
Ice
accidents from
aerodynamic braking and
airplane performance influenced by
airspeed drop from
approach and landing and
avoidance of
cloud tops
cold front and
cloud deck
departure and takeoff and
descent and
drag created from
engine failure and
fluid anti-icing and
flying away from
forecast advances for
formation of
fronts and
hand-flying and
heat for
kinds and classes of
mountains and 180 degree turn away from
orographic effect and
propellers covered in
pulsating boots breaking up
radio mast covered in
snow haze and
taxiing and
ATC advised of
temperature and
vibrations from
warm front and
windshield and
IFR. See Instrument Flight Rules
ILS. See Instrument landing systems
Indicated airspeed (IAS)
Inertial Guidance
Inertial Reference Systems (IRS)
Inertial Reference Units (IRU)
Instantaneous Vertical Speed Indicator (IVSI)
Instrument. See Equipment and instrumentation
Instrument approach
Instrument Flight Rules (IFR)
alternate takeoff requirement for
en route weather and
MVFR and
safety of
VFR compared to
Instrument flying:
departure and takeoff and
limitations of
Instrument landing systems (ILS) approach
Instrumentation. See Equipment and instrumentation
International Civil Aviation Organization (ICAO)
Intertropical Convergence Zone (ITCZ)
Intertropical Front
IRS. See Inertial Reference Systems
IRU. See Inertial Reference Units
Isobars:
barometric pressure connected by
CAT and
on weather map
wind and
Isolated thunderstorm
ITCZ. See Intertropical Convergence Zone
IVSI. See Instantaneous Vertical Speed Indicator
Jet inlets
Jet stream:
clear air turbulence and
location of
above mountain waves
Jetstream
Journal of Aeronautical Meteorology
LAMP. See Localized Aviation MOS Program
Landing. See Approach and landing
Landing gear retraction, rate of climb and
Landing place. See also Airport
fields as
other than airport
roads as
Large-area weather
Lateral Navigation (LNAV)
LDS. See Lightning detection system
Learning to fly weather
ATC and
bad en route
bad to good rule
good to bad rule
good to good rule
thunderstorms
Lee waves
Legal minimums
Lentricular cloud
Lieurance, Nieut
Life cycle, of thunderstorms
LIFR. See Low Instrument Flight Rules
Light Sport Aircraft (LSA)
Lightning. See Electrical discharge
Lightning detection system (LDS)
accuracy of
benefit of
cloud to ground and intra-cloud detection by
false reporting of
improvements of
lightning rate and
limitations of
range of
spherics used by
as supplement
visual detection compared to
Lightning Mapping
Lindberg, Charles
Line-Orientated Flight Training (LOFT)
Line-up and wait
Link Trainers
Little, Dave
LLWAS. See Low-Level Wind Shear Alert System
LNAV. See Lateral Navigation
Localized Aviation MOS Program (LAMP)
LOFT. See Line-Orientated Flight Training
Logical thinking
Looking for pilot reports
Low Instrument Flight Rules (LIFR)
Low-Level Wind Shear Alert System (LLWAS)
Low-pressure system
Low-visibility operations
Lows:
large areas of
occlusion and
slowing down of
weather map of
LSA. See Light Sport Aircraft
Maps. See Charts and maps
Marginal Visual Flight Rules (MVFR)
ceiling and
IFR and
as not static
METAR. See Aviation Routine Weather Report
Meteorologist:
asking why and if questions to
at ATC
big weather picture and
confidence of
consulting during en route weather
local knowledge of
NWS training
private pay for
satellite knowledge by
MFD. See Multi Function Display
Microburst:
dry compared to wet
indication of
Midwest wind flow
Missed approach
autopilot failure and
pilot’s practice with
in thunderstorms
Mode S
Model Output Statistics (MOS)
MODELS
Moisture, instruments predicting
MOS. See Model Output Statistics
Mountain wave
action of
air and
awareness of
distance wavelength of
flying out of
jet stream above
visualization of
Mountains. See also Ridges
altitude and
ice and
rotor around
single peak of
turbulence near
VFR and
wind speed increases around
Multi Function Display (MFD)
MVFR. See Marginal Visual Flight Rules
National Centers for Environmental Prediction (NCEP)
National Lightning Detection Network
National Oceanic and Atmospheric Administration (NOAA)
National Transportation Safety Board (NTSB)
National Weather Service (NWS)
Nav Canada
NCEP. See National Centers for Environmental Prediction
NDB. See Nondirectional beacon
NexGen. See Next Generation Air Traffic System
NEXRAD. See Next Generation Radar
Next Generation Air Traffic System (NexGen)
Next Generation Radar (NEXRAD)
aircraft presentations of
ATC use of
base reflectivity
big weather picture from
composite reflectivity of
image of
limitations of
modes of
mosaic accuracy of
readings from
thunderstorm areas identified by
time lag of
upgrades for
Night flying
approaching and landing
horizon view and
instrument lighting and
thunderstorms and
VFR for
Nimbus clouds
NOAA. See National Oceanic and Atmospheric Administration
Non-precision approaches
Nondirectional beacon (NDB)
North Hemisphere, pressure areas in
Northeast Corner, fronts in
Notices to airmen (NOTAMS)
NTSB. See National Transportation Safety Board
NWS. See National Weather Service
Occlusions
Off-airport landing
Old map thoughts, valid
Orographic effect
ice and
Outlook Briefing
Overshooting landing
Paper charts
electronic charts compared to
from newspaper
PAPI. See Precision Approach Path Indicator
PFD. See Primary Flight Display
Pilot Weather Report (PIREPS)
Pilots:
action plan of
air movement visualization by
alert
bashfulness of
capability of
competition among
distraction exercises and
electronic seduction of
en route weather view of
equipment and ability of
experiences of
feelings influencing performance of
flexibility of
flying basics and
glider
hand-flying by
instinct of
instrument flying proficiency of
investigation by
limitations of
logical thinking of
meteorological duties of
missed approach practice by
mistakes of
passiveness of
plane monitoring by
practice by
responsibility of
self-checking by
sense of control needed by
simulators used by
spotter
stress of
test maneuvers for
training of
weather knowledge of
weather philosophy of
as weather-wise
wind consciousness of
workload of
PIREPs. See Pilot Weather Report
Pitot heat
Planetary boundary layer (PBL)
Plasticized charts
Polar Continental
Pollution, visibility and
Power source, for instruments
back up for
batteries
electrical
failure of
glass cockpit PFD screen
vacuum-powered
Precipitation:
anti-icing needed for
ATC levels of
in dry climate
frozen
visibility and
Precision Approach Path Indicator (PAPI)
Preflight briefing
Prefrontal squall lines
avoidance of
development of
rules for
Pressure-level charts
Pressure systems, on weather maps
Primary Flight Display (PFD)
Primary flight group
proficiency maintenance needed for
test maneuvers for
Primary Weather Product
Prognosis Charts
Propeller
anti-ice blades for
fixed pitch
ice and
Radar. See also Airborne radar; Next Generation Radar
top of thunderstorm
Radiation, cooling by
Radio:
departure and takeoff and
frequency of
ice covered mast
static and
VFR without
Rain:
airborne radar detection of
avoidance of
turbulence and
Ram Air Turbines (RAT)
Range:
airplane performance and
departure to destination
distance and
fuel to alternate
during holding
reserve over the alternate
RAOB. See Rawinsonde observation
RAT. See Ram Air Turbines
Rate of climb, landing gear retraction and
Rawinsonde observation (RAOB)
Reflectivity
Reserve over the alternate
Ridges:
headwinds and
sinks around
tailwinds and
turbulence near
Roads, as landing place
Rotor:
around mountains
turbulence in
visibility of
Rough-air flying
Route:
ATC-cleared
canned
discontinuity
Runway:
alignment
clearing
minimum practices and
surface of
Runway Visibility Range (RVR)
Satellite:
best use of
big weather picture from
images shown by
infrared
looping of
meteorologist knowledge of
time stamp for
VFR and
water vapor display and
weather movement images from
Sea breeze fronts
Sea level, temperature at
Season, weather influenced by
Sectional chart
accuracy of
GPS navigation compared to
Self-briefing, flight planning and
SIDs. See Standard Instrument Departures
Significant Meteorological Information (SIGMET)
Simulators:
Boeing 777
media training and
used by pilots
for wind shear
Single-axis autopilots
Single-pilot operation, in two-pilot world
Sinking air
Situational awareness
Skew-T log-P
Slaved gyro
SLD. See Supercooled Large Droplets
Snow:
blowing off wing
from clouds
departure and takeoff in
haze
VFR in
visibility in
before warm fronts
SPC. See Storm Prediction Center
Special Weather Reports (SPECI)
Spotter pilot
Standard briefing
Standard Instrument Departures (SIDs)
Standard Terminal Arrival Routes (STAR)
Standing waves
STAR. See Standard Terminal Arrival Routes
Stark, Howard
Static, radio and
Static tube
Storm Prediction Center (SPC)
Stormscope
Stratus clouds
Strike Finder
Sublimation
Supercooled Large Droplets (SLD)
Supplementary Weather Products
Surface charts
Surface wind:
flow
fronts and
gradient wind and
temperature of
Synopsis
studying of
weather information and
Synoptic and Aeronautical Meteorology (Byer)
Synoptic Surface Chart
Synthetic vision
TAA. See Technically Advanced Aircraft
TAF. See Terminal Aerodrome Forecast
TAF TDA. See Terminal Aerodrome Forecast Tactical Decision Aid
Tailwinds:
fuel usage influenced by
ridges and
Takeoff. See also Departure and takeoff
airport rushing
IFR requirement for
wind shear hazard for
Taxi time:
checklist read through
ice and
visualization and
TCAS. See Traffic Collision Avoidance System
TDWR. See Terminal Doppler Weather Radar
Technically Advanced Aircraft (TAA)
approach and landing of
augmented indications dependence and
charts and maps need
programming verification of
electronic seduction and
flying basics and
learning curve for flying
manual practice with
pilot training and
programming and
VFR with
Technology:
equipment and instrumentation influenced by
thunderstorms and
weather information influenced by
Teletype sequences
Television weather
Temperature
air molecules and
altitude and
density and
dewpoint relationship with
engines and
ice and
inversion of
at sea level
surface wind and
water and land differences in
Terminal Aerodrome Forecast (TAF)
Terminal Aerodrome Forecast Tactical Decision Aid (TAF TDA)
Terminal Doppler Weather Radar (TDWR)
Terminal Route Approach Control (TRACON)
Terrain:
adiabatic process influenced by
cities influencing
weather influenced by
Test maneuvers:
in dark
with full instruments
variance of
Thermals
Three-axis autopilot
Three-needle-widths
Thunderstorm detection system
Thunderstorms
air-mass
airborne radar and
airspeed and
approach and landing during
ATC and
autopilot and
avoidance of
bad part of
blow-off clouds of
cell generation in
cloud layers in
clouds surrounding
along cold front
creation of
departure and takeoff during
detection of
don’t race
dry climate and
flight diversion from
flying over
frontal
fronts
growth of
how to fly
isolated
kinds of
landing and
learning to fly weather and
life cycle of
lightning rate and
missed approach in
NEXRAD identification of
night flying and
prediction of
prefrontal squall lines and
radar top of
surface winds and
technology and
tops of
turbulence from
as unstable air mass
velocity of
VFR and
warm front and
wind and
wind shear and
Thunderstorms, flying through
almost through
electrical discharge and
emotions during
entrance to
noise during
potency of
radio static and
Time lag, of NEXRAD
Time of day, weather influenced by
Tornado:
flying above
flying around
unpredictability of
Towers, VFR and
TRACON. See Terminal Route Approach Control
Traffic Collision Avoidance System (TCAS)
Tropopause
airplane performance and
CAT and
charts for
data
passing through
studying of
temperature inversion and
Turbulence:
altitude and
autopilots and
convective-layer
cumulus clouds and
during departure and takeoff
during descent
flying in
fog and
hand-flying in
high-altitude
kinds of
near mountains and ridges
as ocean waves
power changes during
rain and
in rotor
from thunderstorms
upper air
velocity and
Turn and bank instrument
Turn coordinator
Two-pilot world, single-pilot operation in
Undershooting
United States Weather Bureau (USWB)
Universal Time Coordinated (UTC)
Updraft
Upper air turbulence
USWB. See United States Weather Bureau
UTC. See Universal Time Coordinated
VASI. See Visual Approach Slope Indicator
Venturi
Vertical Navigation (VNAV)
Vertical speed
Vertical Speed Indicator (VSI)
failure of
as overlooked instrument
VFR. See Visual Flight Rules
VGSI. See Visual GlideSlope Indicator
Visibility:
approach influenced by
departure and takeoff and
location influencing
low
pollution and
precipitation and
reduction of
of rotors
in snow
VFR and
Visual Approach Slope Indicator (VASI)
Visual Flight Rules (VFR)
autopilots during
electronic use during
emotions during
en route weather and
flight planning for
frequency of
FSS on
GPS navigation and
ideal arrangement for
IFR compared to
information lacking with
limitations of
minimums and
mountains and
navigation with
near cities
for night flying
180 degree turn and
without radio
recommendation on
responsibility of
satellite imagery and
sectional chart for
in snow
in summertime
with TAA
thunderstorms and
on top
towers and
visibility and
wind and
Visual GlideSlope Indicator (VGSI)
VNAV. See Vertical Navigation
VOR navigation
VOR Test Signal (VOT)
Vortex, airplane performance and
VOT. See VOR Test Signal
VSI. See Vertical Speed Indicator
WAAS. See Wide Area Augmentation System
Warm front
climbing into
hazard of
ice and
retreat from
sloping of
snow before
surface of
thunderstorms and
weather characteristics of
wind shear and
Water vapor
Weather. See also Big weather picture
acceptance of
at airport
bad, approaching landing in
bad, taking off
clear, good
clouds influencing
as complicated
continuous watch over
daily look at
flying influenced by
along fronts
fuel usage by
intensity of
judgment of
large-area
late
meteorologist’s local knowledge of
pilot’s knowledge of
pilot’s philosophy of
respect for
season and time of day influencing
study of
terrain influencing
tracking of
VFR and
wind influencing
Weather briefing:
abbreviated
accuracy of
for approach and landing
changes in
code language and
example of
format and code changes
from FSS
“IF” information and
investigation and
official
outlook
preflight
self
sources of
synoptic
television weather and
vague
Weather Channel
Weather Depiction chart
Weather information:
learning where and how
need for
regulations on
sources for
synopsis and
technology influencing
Weather map:
information from
isobars on
of lows
pressure systems and fronts on
as snapshot
Wet microburst:
dry microburst compared to
indication of
Wide Area Augmentation System (WAAS)
Wind shear
airplane and
approach and landing and
avoidance system for
from gusty winds
instruments to help fly through
location and forecast of
overshooting and undershooting with
profile of
simulator for
stalling from
as takeoff hazard
thunderstorms and
warm fronts and
Winds. See also Turbulence
airplane performance influenced by
aloft
approach and landing and
from bodies of water
departure and takeoff and
force of
above friction layer
in frontal system
gradient
gusty
isobars and
Midwest flow of
ocean waves compared to
speed of
surface flow of
thunderstorms and
turbulence, due to
types of
velocity change with height
velocity of
VFR and
weather influenced by
Windshield:
fogging of
ice and
openings of
Wings:
deicers and anti-ice for
hot
snow blowing off
Yaw damper
Zippers, as fronts