PILOT NAVIGATION
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Contents List.
Click on a chapter.
PILOT NAVIGATION
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Units.
Flight Planning.
Position Fixing.
Map Reading.
Chapter 5
Weather.
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PILOT NAVIGATION
Chapter 1
Units
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Units
Most countries still use feet to measure aircraft height and
altitude. Only in Russia and China are you expected to fly
and report altitude in metres.
Units
Most countries still use feet to measure aircraft height and
altitude. Only in Russia and China are you expected to fly
and report altitude in metres.
Units
Most countries still use feet to measure aircraft height and
altitude. Only in Russia and China are you expected to fly
and report altitude in metres.
Despite still using feet to measure aircraft altitude, most
countries have adopted metres to show elevations on maps the British OS map is an example.
Great care is needed because an aircraft being flown in
thousands of feet can be in a very dangerous position if a
navigator reads a mountain top as being 2000 feet instead of
2000 metres!
Safety Altitude
Imagine an aircraft is flying at 2000 feet above sea level
towards a hill with a peak 1000 metres above sea level.
One metre is equal to 3.3
feet, so the 1000 metre
peak is actually 3300 feet
above sea level.
If the pilot takes no
avoiding action the aircraft
will hit the hill 1300 feet
below the peak.
1000m
2000ft
3300ft
Safety Altitude
The Navigators number one priority at all times is to
calculate and ensure the aircraft is above the safety altitude
for the area.
He will take great care to ensure that elevations taken from
maps which have contours and spot heights in metres, are
converted into feet.
Vertical Speed
Vertical speed is measured in ‘metres per minute’ in Russia
and China.
The rest of the world measures vertical speed in ‘feet per
minute’.
Meteorological Reports
Most countries except the USA use metric units for
meteorological reports, for instance:
The USA still reports visibility in miles and feet.
The rest of the world reports visibility in kilometres and
metres.
Aircraft and Fuel
American built aircraft measure fuel in pounds or imperial
tons. Most others use kilogrammes (kgs) or metric tonnes.
Although it would be more correct to measure fuel by its
mass, fuel cannot be weighed when an aircraft is airborne.
The alternative is to measure its volume.
Specific Gravity
Different fuels have different densities or ‘Specific Gravities’.
Specific Gravity (SG) is the ratio between the weight of the
fuel and the weight of the same volume of water.
Water has an SG of 1.0
Jet fuel typically has an SG of about 0.8
This means that a litre of jet fuel will weigh only 80% of the
weight of a litre of water.
Fuel Conversion
Conversion of fuel weight to volume, or between the various
types of units (pounds, gallons, litres etc) can be done in
several ways.
A calculator can be used, or conversion charts in the RAF
Flight Information Handbook.
Alternatively the crew could use a DR Computer.
Pressure
Atmospheric pressure is caused by the weight of air above us.
The higher we go, the less air there is above us.
Atmospheric pressure is greatest at sea level and reduces as
we climb up through the atmosphere.
Pressure can be measured in pounds per square inch (psi),
inches of mercury (the method used in the USA), or millibars.
Millibars are used everywhere outside the USA.
Pressure
This table illustrates how the atmosphere thins with altitude:
Altitude (feet)
Air Pressure (millibars)
Sea level
1013
10,000
700
18.000
500
24.000
400
30,000
300
34,000
250
39,000
200
Pressure
Note that at a typical airliner’s cruising altitude of 34,000 ft
the air outside has only one quarter of the sea level pressure.
Altitude (feet)
Air Pressure (millibars)
Sea level
1013
10,000
700
18.000
500
24.000
400
30,000
300
34,000
250
39,000
200
Pressure
The amount of oxygen available is also only one quarter of
that at sea level. The cabin pressurization system maintains
the oxygen level for the passengers and crew.
Altitude (feet)
Air Pressure (millibars)
Sea level
1013
10,000
700
18.000
500
24.000
400
30,000
300
34,000
250
39,000
200
PILOT NAVIGATION
Chapter 2
Flight Planning
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The Triangle of Velocities
Heading and True Airspeed (HDG/TAS)
Windspeed and
Direction (W/V)
The Triangle of Velocities
Heading and True Airspeed (HDG/TAS)
Drift is the angle
between Heading
and Track vectors
Windspeed and
Direction (W/V)
The Triangle of Velocities
Heading and True Airspeed (HDG/TAS)
Windspeed and
Direction (W/V)
Each vector has both a
direction and a value
(represented by the
length of the arrow).
The Triangle of Velocities
Heading and True Airspeed (HDG/TAS)
Windspeed and
Direction (W/V)
Providing we have four
of the elements of the
vector triangle, we can
find the other two.
The Triangle of Velocities
Heading and True Airspeed (HDG/TAS)
Windspeed and
Direction (W/V)
The quickest and most
accurate way of solving
the vector triangle is to
use the Dalton DR
Computer.
Flight Planning
For private pilots and
light military trainers,
flight planning is
carried out using the
Pilot Navigation Log
Card.
Flight Planning
The Pilot Navigation
Log Card is purely for
use by the pilot,
ensuring that he has
all of the necessary
details readily
available in the
cockpit, to complete
the flight safely and
accurately.
Flight Planning
The pilot must enter
the important details
on the log card for
each leg.
He must measure the
tracks from the map
using a protractor and
the distances with
dividers.
Flight Planning
Temperature is required
in order to calculate the
True Airspeed (TAS)
from the Calibrated
Airspeed (CAS).
Fuel Planning
The time for each leg
and the fuel required is
also calculated and
logged on the card.
Running out of fuel in
a car is inconvenient, in
an aircraft it is
disastrous.
Fuel Planning
The timings on the log
cards also help the
pilots pass accurate
estimates of time of
arrival (ETA’s) at
waypoints or
destinations.
Safety Altitude
The safety altitude is
calculated by adding
1000 feet to the highest
elevations (mountains,
TV masts etc) on or
near the track and
rounding up to the
nearest 100 feet.
Safety Altitude
For instance, if the
highest obstacle near
the track is 1750 feet,
the safety altitude is:
1750 + 1000 = 2750 ft.
Rounded up to the
nearest 100 ft this
becomes 2800 feet.
Safety Altitude
If meteorological
conditions deteriorate
the pilot must always
be prepared to climb
above the safety
altitude.
Air Traffic Control Flight Plan
Before a pilot commences his flight he must submit an ATC
Flight Plan so that ATC units along his route, and at his
destination, have details of his intended flight.
The Flight Plan is faxed or electronically transmitted to all
of the ATC Centres en-route.
The Flight Plan includes the aircraft callsign, type of
aircraft, time and place of departure, speed and altitude,
intended route and ETA at destination. It also includes safety
information such as the numbers of people on board and the
types and quantities of emergency equipment carried.
PILOT NAVIGATION
Chapter 3
Position Fixing
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Position Fixing
In the pioneering days of aviation, aircraft could not fly
unless the pilot could see the ground, as map reading was
the only way of navigating.
Great strides were made during World War II, but it was not
until the 1970’s that world-wide coverage was achieved with
a fixing aid known as Omega.
This has now been superseded by Satellite Navigation
(SATNAV) and the Global Positioning System (GPS).
Visual Fixing
By using a map to positively identify a feature on the ground
below, you are making a visual fix known as a pinpoint.
The pinpoint is still a very reliable way of fixing one’s
position, particularly in the early days of training.
Radio Aids
The next time you listen to a small portable radio, try
turning the radio through 360 degrees.
You will find that there are two points in the circle where
reception is poor, and two points where reception is best.
This is because the aerial is in the form of a horizontal bar.
Radio Aids
The Radio Direction Finder (or radio compass) works on the
same principle to find the direction of the aircraft from a
beacon.
By using lines from two further beacons, preferably at about
60 degrees from each other, a ‘three position line fix’ can be
plotted to accurately locate the position of the aircraft.
VOR/DME and TACAN
A more modern method
of position finding
utilises VOR/DME
(civilian) or TACAN
(military) beacons.
Both give the same information, namely the magnetic bearing
of the aircraft from the beacon and the range.
Astro Navigation
Astro navigation works on the principle of using a sextant to
measure the angle of the sun or stars to determine position.
Perhaps the only advantage of astro navigation is that it
cannot be jammed.
It has been superseded by GPS.
Radar Navigation
Airborne radar has been refined to such a stage that ground
returns received by an aircraft ca be matched to a
‘computerised map’ enabling an accurate fix to be obtained
simply at the press of a button.
The major disadvantage of this system is that the radar
transmissions can be detected by the enemy.
Long Range Fixing
During the 1950s and 1960s a number of long range ‘area’
navigation systems were developed:
Gee, Decca, Loran and Omega.
All worked to a similar principle – measuring the time it
takes two synchronised signals to arrive from two different
transmitting stations to give a fix.
Global Positioning System (GPS)
With airborne microcomputers and the network of Global
Positioning Satellites it is now possible for even an unskilled
operator to obtain fixes to within a few metres.
Active / Passive Systems
The development of radar-homing missiles has necessitated
the development of even more sophisticated electronic
warfare (EW) countermeasures.
Whilst electronic warfare measures can be taken to protect
‘active’ systems, another approach is to use only ‘passive’
systems.
‘Passive’ systems do not transmit, merely receiving signals
such as those transmitted by GPS satellites. Combining these
with a triple Inertial Navigation System (INS) will give a
very accurate position fix.
Navigation Training
Despite the availability of accurate navigation systems a
student pilot will spend a great deal of time, especially in
the early stages of his training developing the basic skill of
map reading.
PILOT NAVIGATION
Chapter 4
Map Reading
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Map Reading
You can make the same mistakes map reading in the air as
on the ground, but with the extra mental pressure that there
is no time when you are flying to have a discussion about
your location.
Altitude
The best features to select for map reading will depend upon
whether the aircraft is at high or low altitude.
At low level it is important to choose features which have
vertical extent – chimneys, hills, power stations etc.
At high level vertical features cannot be seen and larger
features are needed – lakes, woods, islands etc.
Unique?
The most important characteristic of a map reading feature is
that it is unique and cannot be confused with any similar
nearby features.
Contrast and Colour
Of the natural features used in map reading rivers and
coastlines are generally the most useful.
They show the greatest contrast and colour change between
themselves and the land.
Map Scales
Special maps are produced for map reading from the air.
Emphasis is placed on features more easily identified from
the air.
They are normally made to a much smaller scale – typically
1:500,000
Timing Marks
Before embarking on a flight in an aircraft without
sophisticated navigation aids, a student will put timing or
distance marks along each of the legs of his route.
10
20
30
40
Timing Marks
If he loses his place along his track he need only consult his
watch, work out the time since his last waypoint and that
will tell him where to look at the map.
10
20
30
40
PILOT NAVIGATION
Chapter 5
Weather
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The Atmosphere
Pure air consists of 79% nitrogen, 20% oxygen and 1%
other gases.
The major variable in the atmosphere that affects weather is
water in all of it’s forms.
The air pressure at sea level is caused by the weight of the
air above us. With increasing altitude the pressure reduces,
and so does the temperature.
Water Vapour
Air holds water vapour as an invisible gas. The warmer the
air, the more water vapour it can hold.
As air is cooled, its ability to hold water vapour is reduced.
Eventually it becomes ‘saturated’ and can hold no more
water vapour – this is the ‘dew point’.
If the air continues to be cooled below it’s ‘dew point’ then
visible droplets of water start to form – dew, mist, fog or
clouds.
Water Vapour
There are four ‘trigger actions’ which cause air to rise:
Turbulence
Convection
Orographic Uplift
Frontal Uplift
- heating
- hills and mountains
- cold or occluded fronts
In each case temperature and pressure fall until the ‘dew
point’ is reached, and at that altitude the base of the cloud is
formed. Cirrus (high level clouds) consist of ice crystals, but
most clouds consist of tiny visible droplets of water.
Turbulence
Convection
Orographic Uplift
Frontal Uplift
Turbulence
Convection
Orographic Uplift
Frontal Uplift
Turbulence
Convection
Orographic Uplift
Frontal Uplift
Turbulence
Convection
Orographic Uplift
Frontal Uplift
Turbulence
Convection
Orographic Uplift
Frontal Uplift
Turbulence
Convection
Orographic Uplift
Frontal Uplift
Turbulence
Convection
Orographic Uplift
Frontal Uplift
Thunderstorms
Thunderstorms present a variety of hazards to an aircraft.
Thunderstorms
Thunderstorms present a variety of hazards to an aircraft.
They are best avoided by a large margin.
Some of these hazards are:
Icing
- airframe and engine
Precipitation
- usually hail
Turbulence
Lightning
Severe downdrafts
Thunderstorms
Modern aircraft
carry weather
radar to assist in
avoiding
thunderstorms.
Thunderstorms
The amount of lift
produced by a
wing significantly
reduced as ice
accumulates. The
stalling speed is
also increased.
Thunderstorms
This ice accumulated on a wing leading edge during flight.
The pilot was fortunate to land safely.
Thunderstorms
Thorough de-icing prior to flight is vital.
Thunderstorms
The importance of avoiding thunderstorms is illustrated in
the following photographs. They are of a BaxGlobal plane
that took off from Calgary, Canada and encountered hail.
The pilot managed to return and land at the Calgary airport.
This damage was inflicted upon the plane within 5 minutes
of take off.
Thunderstorms
Thunderstorms
Thunderstorms
Thunderstorms
Thunderstorms
Thunderstorms
Thunderstorms
Thunderstorms
Thunderstorms
Two Asiana Airlines' pilots were awarded citations for
safely landing their aircraft damaged by hailstones.
There were 200 passengers on board.
Lightning strikes on aircraft do not normally cause major
damage. This strike damage on the nose of a NOAA
Hercules is typical.
Heavy rain can flood runways and reduce wheel braking
effectiveness. This is known as aquaplaning.
Heavy rain can flood runways and reduce wheel braking
effectiveness. This is known as aquaplaning.
Heavy rain can flood runways and reduce wheel braking
effectiveness. This is known as aquaplaning.
Heavy rain can flood runways and reduce wheel braking
effectiveness. This is known as aquaplaning.
Aquaplaning video
Landing at this US airport would not be recommended!
Landing at this US airport would not be recommended!
Isobars
Isobars join points of equal pressure (just as contours join all
points of equal height) and help meteorologists and pilots
understand how the air is moving.
Isobars
Isobars join points of equal pressure (just as contours join all
points of equal height) and help meteorologists and pilots
understand how the air is moving.
In the northern
hemisphere air
circulates clockwise
around anticyclones
(high pressure
areas).
H
Isobars
Isobars join points of equal pressure (just as contours join all
points of equal height) and help meteorologists and pilots
understand how the air is moving.
And circulates
anticlockwise
around cyclones
(low pressure
areas).
L
Isobars
Isobars join points of equal pressure (just as contours join all
points of equal height) and help meteorologists and pilots
understand how the air is moving.
The easy way to
remember this is
that if you stand
with your back to
the wind the Low
pressure is on your
Left.
L
Isobars
Isobar patterns represent the wind at 2000 ft above the surface.
The direction of the lines gives the direction of the wind and
the closer the lines are together the stronger the wind
Low
Isobars
On the surface the wind will be about 25% less strong than at
2000 ft due to the effects of friction.
It will also have ‘backed’ about 25 degrees compared with
the 2000 ft wind.
Low
Isobars
For instance, if the 2000 ft wind is 270/20
the surface wind will be 245/15
Low
TAFs and METARs
Weather information is passed from the met office to aircrew
in the form of Terminal Area Forecasts (TAFs) and
Meteorological Actual Reports (METARs).
Standard codes are used for brevity, for instance
‘CAVOK’ means that there is no cloud below 5000 feet and
visibility is at least 10 km. (Cloud And Visibility OK)
TAF and METAR Decodes
BR
DZ
HZ
FU
RA
Mist
Drizzle
Haze
Smoke
Rain
FZ
TS
FG
SH
SN
Freezing
Thunderstorms
Fog
Shower
Snow
- Slight
+ Heavy
The codes can be used in combination
e.g. + RASH means heavy rain showers.
PILOT NAVIGATION
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PILOT NAVIGATION
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