1. Senior/Master Air Cadet
PILOT NAVIGATION
Senior/Master Air Cadet

2. Know the basic features of air navigation and navigational aids
Learning Outcomes
Know the basic features of air navigation and navigational aids
Understand the techniques of flight planning
Understand the affects of weather on aviation

3. Introduction
This portion of the syllabus will now tie the previous 3 subjects together

4. Units

5. Units
At school you will have been taught that in the modern world everything is measured in metric units
However in real life many people use non metric measures. An example of this is the use of miles & mph in the UK

6. Units
This unit will look at the units commonly used for:
vertical distance
weather
speed
fuel
aircraft weight
pressure

7. Vertical Distance and Speed
In aviation horizontal distances are measured in nautical miles and speed in knots
One minute of arc measured at the centre of the earth equals 1 nm on the earth's surface
These units are based on the length of a “GREAT CIRCLE” on the surface of the earth

8. Vertical Distance and Speed
In the vertical axis the majority of countries use feet to measure height or altitude. Only the former communist countries use metres

9. Vertical Distance and Speed
It must be noted that many countries who use feet have changed their maps to show elevation in metres, - such as the UK OS maps

10. Vertical Distance and Speed
Great care is needed because an aircraft flown in thousands of feet can be in a very dangerous position !
if a navigator reads a mountain top at 2000’ when it is 2000 metres which is about 6000’!

11. Vertical Distance and Speed
Terrain clearance is done with great care & the navigator’s number one priority
For the calculation of the Safety Altitude there should be no doubt

12. Vertical Distance and Speed
Vertical Speed uses similar units to Vertical Distance
Feet per Minute

13. Vertical Distance and Speed
For most military aircraft, Vertical speed Indicators which show rate of climb or descent are calibrated in
Thousands of Feet per Minute

14. World-wide the Met Office has changed to metric units
Meteorological Units
World-wide the Met Office has changed to metric units
With the major exception of the USA
However even the Met Ofice must continue to use feet for altitude & knots for windspeed

15. Aircraft & Fuel
Strictly speaking aircraft & fuel should be measured by mass
For aircraft the units used depend on the country of manufacture
In practical terms it is weight
(the effect of gravity on mass )
that we use
Most US aircraft (70% of the worlds total ) use pounds or imperial tons. The rest use kilograms (kg) or metric tonnes

16. For fuel the situation is more complicated
Aircraft & Fuel
For fuel the situation is more complicated
In theory it should be measured by mass as the amount of thermal energy in one unit of fuel relates directly to its mass!!!

17. Aircraft & Fuel
The fuel delivered to the aircraft, from the bowser, is measured by volume,
as in cars.
In cars we measure the fuel volume in litres (or gallons) & then calculate the fuel use in km per litre (or mpg )

18. Aircraft & Fuel
However the use of volume in the air is not accurate enough as the type of fuel
& the temperature affect the
mass per unit volume
AVTUR
AVGAS
In other words the density of fuel varies from type to type
Even if one type of fuel is always used, its density will change with temperature changes

19. weight of the same volume of water
Aircraft & Fuel
Different types of fuel each have a Specific Gravity ( SG )
Water has a SG of 1.0
A typical jet engine fuel has a SG of 0.80
SG is a measure of the ratio between
the weight of the fuel and the
weight of the same volume of water

20. Aircraft & Fuel
Conversion is done by calculator, a DR computer or the chart in the RAF flight information handbook
This means a litre of jet fuel weighs 80% of the weight of a litre of water

21. Various gasses & fluids in aircraft are pressurised
Pressure
Pressures are expressed in different units according to the country of origin
usually PSI or Bars
Various gasses & fluids in aircraft are pressurised

22. Our main concern is the pressure in the atmosphere
Air Pressure
Our main concern is the pressure in the atmosphere
The higher we go the less air there is & so pressure reduces as we gain height

23. The average pressure at sea level is 1013 HPA
Air Pressure
Air Pressure is measured Hectopascals (HPA)
which has recently replaced Millibars (MB)
The average pressure at sea level is 1013 HPA
Hectopascals is in general use outside the USA which uses Inches of mercury
Millimetres of Mercury is also used

24. If it was not for pressurisation, all aboard would be unconscious
Air Pressure
AIR PRESSURE
IN HPA
ALTITUDE
IN FEET
SEA LEVEL
1013
10,000
700
18,000
500
24,000
400
30,000
300
34,000
250
39,000
200
Note an airliner at 34000ft is pressurised to 5000ft and so the amount of oxygen at that altitude is a quarter of that at sea level
If it was not for pressurisation, all aboard would be unconscious

25. Air Pressure
At a cruising altitude of 39,000 ft, a Boeing 767's cabin will be pressurised to an altitude of 6,900 ft
Combat aircraft cockpits are usually pressurised considerably less than airliners, with crews breathing a pressurised air/oxygen mix through masks

26. Conclusion
Aviation is the only major area of science still using such a wide variety of units
Until countries agree to common units for their instruments, confusion is always possible in flight
There is a slow movement to metrication

27. Check of Understanding
In aviation how are horizontal distances and horizontal speeds measured?
horizontal distances are measured in nautical miles
speed in knots

28. Check of Understanding
How do the majority measure vertical distances?
the majority of countries use feet to measure height or altitude

29. Check of Understanding
How are Vertical Speed Indicators calibrated?
For most military aircraft Vertical Speed Indicators, showing rate of climb or descent are calibrated in
Thousands of Feet per Minute

30. Check of Understanding
In practical terms, how are aircraft and fuel measured?
In practical terms it is weight

31. Check of Understanding
What is Specific Gravity?
a measure of the ratio between the
weight of the fuel
and the
weight of the same volume of water

32. End of Learning Outcome 1