Safety Down Day
Practical Aviation Weather
DEWG CAP
October 16th, 2010
Practical Aviation Weather
The Weather……
• Why We Review
• When We Review
• Weather Information Services
• Visual Weather
• Microbursts and Thunderstorms
• Radar Services
• Icing
Practical Aviation Weather
Why Review the Weather…..
• Required preflight action – FAR 91.103
• Significant factor in CAP mission success (VFR
operations)
• Could be hazardous
Stained undergarments
Damaged Aircraft
Loss of life
• Just the right thing to do to insure safety of flight
Practical Aviation Weather
When Do We Review Weather?
•
•
•
•
•
The day(s) before
As part of preflight planning
Before take-off
Enroute
Before Landing
What’s
the Big
Picture
Practical Aviation Weather
Weather Information
Services
Practical Aviation Weather
Weather Information Resources?
By Phone
• Automated Flight Service Station (AFSS) nationwide 1-800-WX-BRIEF
(922-7433).
• CSC DUATS Dial-up: 1-800-767-9989
• DTC DUATS Dial-up: 1-800-245-3828
(maintains a record which fulfills preflight requirement of acquiring weather
and airport information.)
By WEB
• Aviationweather.gov
• Intellicast, Unisys, NOAA, Aviation Digital Data Service, Weather
Channel
Enroute
• EFAS (Enroute Flight Advisory Service) 122.0 MHz
• Available via Remote Communications Outlets (RCO) for regional
coverage
Practical Aviation Weather
Information Needed by Briefer
1. Aircraft registration number or pilot’s name
2. Aircraft type
3. Type of flight planned (VFR or IFR)
4. Departure airport
5. Route of flight
6. Destination
7. Flight altitudes
8. ETD, ETE, and ETA
Practical Aviation Weather
Visual Weather
Many types of weather phenomena
can be determined visually
• cloud types and their affect on flight
conditions
• thunderstorms and clouds with
extensive vertical development
• microbursts and wind shear, in
some cases
Virga, Rain showers, Heavy
precipitation, Blowing dust or
rings of dust
Moderate or greater turbulence,
Temperature/dewpoint spread
between 30° and 50° Fahrenheit
Practical Aviation Weather
IF………Microbursts or Wind Shear
Immediately execute the recommended recovery
procedure or a go-around if deviations from normal
configurations occur in excess of the following:
Takeoff/Approach
• ± 15 knots indicated airspeed
• ± 500 f.p.m. vertical speed
• ± 5 degree pitch attitude
Approach
• ± 1 dot glideslope displacement
• Unusual throttle position for a significant period of
time
Practical Aviation Weather
Microbursts and
Wind Shear
Ref – Pilot Windshear
Guide (AC 00-54)
Practical Aviation Weather
Avoiding Thunderstorm Accidents
According to the 2005 Nall Report, within the category of GA, pilotrelated accidents, “Nearly 25 percent of fatal weather-related
accidents were due to encounters with thunderstorms.
All thunderstorms are dangerous!
• Radio communication can be lost due to 'precipitation' static;
it will work again after exiting the storm.
• Turbulence will be so severe that the pilot very likely will not
be able to read the flight instruments.
• The aircraft might sustain structural damage.
• Most importantly, the pilot might lose control of the aircraft.
Practical Aviation Weather
Avoiding Thunderstorm Accidents
Never intentionally fly into a thunderstorm. The following
options always exist:
• Divert and land
• Navigate around the thunderstorm
• Reverse course (180-degree turn)
Practical Aviation Weather
Avoiding Thunderstorm Accidents
• Do not attempt to climb above a thunderstorm. Aircraft
generally cannot climb to the necessary altitudes.
• Do not land or take off in the face of an approaching
thunderstorm. A sudden gust front of low-level turbulence
could cause loss of control.
• Do not fly without airborne radar into a cloud mass containing
scattered, embedded thunderstorms.
• Avoid all thunderstorms by at least 20 miles (on the upwind
side).
• Circumnavigate the entire area if a thunderstorm covers 60%
of the scope.
Practical Aviation Weather
Radar Services
Practical Aviation Weather
Radar Services and Diversion
• Whose responsibility it is to divert aircraft around severe
weather conditions, and be sure they know the answer:
The Pilot!
• ATC's primary responsibility is to separate IFR traffic.
• Weather avoidance services are not guaranteed; ATC
provides them only if their workload permits.
• Pilots must request weather avoidance services from each
controller on the route.
• Be aware that “direct to when able” clearances from ATC
mean that the controller is assuming that you are avoiding
storms on your own.
Practical Aviation Weather
Radar Services and Diversion, cont’d
• The key limitation of ATC radar is its line-of-sight
• Any mountains between your aircraft and ATC radar prevent ATC from
detecting the weather at your location.
• Radar sites located on mountaintops, which can be over 8,000 MSL, can
'overshoot' precipitation located in valleys or on the far side of intervening
mountains.
• Approach control radar (ASR) shows light, moderate, heavy, and extreme
precipitation in real-time.
• Reroute radar (ARTCC) includes Weather and Radar Processor (WARP)
radar, which integrates NEXRAD weather with center radar.
• Shows moderate, heavy, and extreme precipitation.
• Is not real-time; it is updated every 11 minutes during fair weather and every
6 minutes during precipitation.
Practical Aviation Weather
Icing
Practical Aviation Weather
Avoiding Icing Accidents
Prime Directive………
Do not fly into known icing conditions unless your aircraft is
certified for known icing operations
……even then…..
Practical Aviation Weather
Avoiding Icing Accidents
How dangerous is icing?
Extremely Dangerous!
• It always degrades performance, but it often leads to
catastrophic, unrecoverable loss of control.
• No aircraft is immune.
• Certification for flight in “known icing” provides little defense
against severe icing. In fact, the definition of severe icing is
that it overwhelms ice protection systems.
• Ice protection systems on most GA aircraft will not save you;
they just buy you a little time to get out of icing conditions.
Practical Aviation Weather
Avoiding Icing Accidents
• Pilots must avoid icing conditions, but if they cannot,
they must get out quickly!
• Unfortunately, no onboard systems can definitively
pinpoint icing conditions.
• Pilots must maintain situational awareness and plan a
way out of icing conditions.
Practical Aviation Weather
Avoiding Icing Accidents
Rime ice is an opaque (milky looking)
ice with a rough, porous texture.
• Forms when water droplets freeze
immediately upon impact with the
Airframe (most likely below –15
degrees Celsius).
• Is more likely to form where anti-icing
or deicing equipment is located.
• Seriously affects wing
aerodynamics.
Practical Aviation Weather
Avoiding Icing Accidents
Clear ice is a transparent or translucent
ice with a smooth texture, which may
contain streaks or bumps of hard ice.
• Forms when water droplets freeze
slowly on the airframe (most likely
between 0 and –5 degrees Celsius).
• Can spread beyond the location of antiicing or deicing equipment.
• Is very hard and heavy.
• Adheres strongly to the airframe.
• Has more serious effects on
aerodynamics than rime ice.
Practical Aviation Weather
Avoiding Icing Accidents
Mixed ice is a combination of rime and
clear ice that forms between –5 and –15
degrees Celsius.
Practical Aviation Weather
Avoiding Icing Accidents
The effects of all types of ice, even on aircraft certified to be
“ice protected,” can include:
•Decreased performance
•Increased drag
•Reduced lift
•Increased fuel consumption
•Catastrophic, unrecoverable loss of control:
•Tail stall (a condition that pilots are not trained to
recognize or recover from)
•Loss of roll control due to ice formation on
thinner, outer portions of wing
Practical Aviation Weather
Avoiding Icing Accidents
•Decline an ATC clearance that puts or keeps you in icing conditions.
•Climb quickly through areas conducive to icing. To do so:
 Do not accept intermediate altitudes.
 Delay climbing if you are able.
 Accept an “inconvenient” heading to get to a safe altitude.
•Descend quickly through areas conducive to icing. To do so:
Prepare for a faster descent.
Delay descent on an approach as necessary.
Practical Aviation Weather
Avoiding Icing Accidents
Pilots have five options for getting out of icing conditions:
Climb: To get above clouds, To get reserve altitude, To get to colder
conditions above where icing is not a problem (below –20 degrees
Celsius)
Descend: To get to warmer conditions (above 2 degrees Celsius),
keeping in mind that this is not an option if you are already at MEA.
Continue: If conditions ahead are better than conditions behind.
Divert: If icing conditions are likely on approach to destination.
Return: The moment you notice conditions are worse than expected.
Practical Aviation Weather
Avoiding Icing Accidents
• If you can’t maintain altitude, descend under control. Do not
stall!
• Hand-fly the airplane in icing conditions. Autopilot could mask
an impending upset.
• Remember that the stall warning system can be unreliable. It
can freeze, and your wing can stall at lower angles of attack.
• Be alert for tail stall. The tail has a smaller leading edge, so ice
is probably already accreting on it if you see ice on a wing.
Note that: Extending flaps aggravates tail stall.
Adding power aggravates tail stall.
• Train to Recognize and Recover from tail stalls.
Practical Aviation Weather
Avoiding Icing Accidents
Symptoms of an Impending Tail Stall
• Lightening control loads
• Difficulty trimming.
• Pilot-induced (pitch) oscillations.
• Buffets in yoke, not airframe (The yoke pulls forward, sometimes
smashing to the stop and can’t be pulled back; forces of more than
100 lbs. can occur.)
• Very sudden pitch-down, which can be unrecoverable on
approach.
Recovery is Opposite of Wings Stall
•Pull the Power
•Pull the Yoke
•Reduce the Flaps
Practical Aviation Weather
The Weather……
• Why We Review
• When We Review
• Weather Information Services
• Visual Weather
• Micro bursts and Thunderstorms
• Radar Services
• Icing
Practical Aviation Weather
Thanks…..Capt Dan