1. AIR NAVIGATION
Part 1
Distance Speed & Time

2. LEARNING OUTCOMES On completion of this unit, you should:
Be able to carry out calculations to determine aircraft distance, speed and time
Understand the principles of vectors and the triangle of velocities to establish an aircraft’s track and ground speed

3. LEARNING OUTCOMES Understand the principles of the 1 in 60 rule
Understand the types of compass systems used for air navigation, how they work and their limitations
Know the hazards that weather presents to aviation

4. RECAP
Latitude/Longitude grid divides the surface of the Earth into degrees and minutes
One minute of latitude represents one nautical mile (nm)
1 degree of latitude (60 minutes) equals 60nm

5. As a complete circle is 360°
then 360 x 60 gives the circumference of the Earth as nm
(approx statute miles).

6. Lines of Longitude are sometimes referred to as MERIDIANS
When recording your position – the line of Latitude must be given first.
The starting point goes through Greenwich and is referred to as the:
“Prime Meridian”
This slide could be used as a check of understanding:
Instructor asks what at lines of longitude sometimes referred to?
When recording your position, which meridian is given first?
Where is the starting point for these Meridian and what is first one called?

7. If Sqn has these maps, then each cadet could have one to look at.
Notice that on nautical maps or
charts there are no scales on the borders, so we have to use the nm scale which is
shown along each meridian. Note also that the scale along the parallels is not used
because convergence shrinks the scale considerably in the British latitudes, and
even more near the Poles

8. Finding Distance Between 2 Points
Use a ruler and dividers
If you do not have any equipment, using the marks along the edge of any piece of paper
Instructor to demonstrate using ruler and dividers – if they have them.
Instructor to demonstrate using paper
Students can have a go.

9. Change of Latitude
If two places are on the same meridian then it is possible to calculate the distance between them rather than having to measure it
For example Torrejon airfield (near Madrid in Spain) is due south of RAF St Athan. These two latitudes are N40º29’ and N51º24’
How would we calculate the distance between them?
Allow students to answer – subtracting one from another.
Calculate the answer

10. To convert 10º 55’ into nautical miles:
Calculation
First Latitude:
N 51º 24’
Second Latitude:
N 40º 29’
Subtracting gives:
10º 55’
To convert 10º 55’ into nautical miles:
10º multiply by 60 = 600
Add the 55’ = 655 nm
Subtracting one lat from another:
In this example: 29’ to 60’ = 31
60’ to 24 = = 55’
Because we carry 1 across we now have 51 – 41 = 10

11. Aircraft Speed
The speed for cars, motorcycles and other land-based vehicles:
Miles per hour
For aircraft, the speed is a measure of:
Nautical Miles per hour – (Knots)

12. Aircraft Speed We cannot use a speedometer to record aircraft speed.
The aircraft flies through the air.
We use an instrument called an Air Speed Indicator (ASI)

13. Aircraft Speed ASI measures the dynamic air pressure A simplified ASI
Dynamic Air Pressure is the pressure caused by forward motion of the aircraft
A simplified ASI

14. Aircraft Speed
In forward flight the pressure above the diaphragm will consist of Dynamic + Static.
Below, the pressure is just Static
The two static pressures cancel out and the diaphragm will move due to the dynamic pressure.
A simplified ASI

15. Aircraft Speed
The movement due to dynamic pressure is amplified and displayed on the instrument as Indicated Air Speed (IAS), reading in knots.

16. Corrections
The reading on the ASI can be in error because of two errors, namely Pressure Error and Instrument Pressure.
Instrument error is caused by poor manufacturing tolerances when the instrument was built.

17. Corrections
Pressure Error previously known as position is caused by sensing incorrect values of static pressure due to the position of the static vents relative to the airflow around the aircraft.
Both errors can be measured by testing the aircraft under controlled conditions and a calibration card with the combined errors is displayed in the cockpit next to the instrument.

18. Calibrated Air Speed
Once the two errors have been accounted for, we are left with Calibrated Air Speed (CAS), formerly known as Rectified Air Speed (RAS).
IAS ± Pressure Error ± Instrument Error = CAS
Thus an IAS of 118 kts with a correction on the calibration card of +2 kts would give a
CAS of 120 kts.
Added notes for Instructor:
A pilot flies using Calibrated Air Speed because it represents the force of the
airflow around the aircraft. The higher the aircraft flies, the less dense the air becomes
and the faster the aircraft has to fly through the air to achieve the same force and
therefore the same CAS. A navigator however, needs to know the actual speed that
the air craft is flying through the air so that he can compare it with his speed over the
ground and hence estimate the wind.

19. True Air Speed (TAS)
To obtain True Air Speed (TAS) from CAS you need to correct for air density changes caused by changes in temperature and altitude.
This can be done by calculation or by
Navigation Computer.

20. TAS
If you are flying at speeds greater than 300 kts, then you need to apply a correction for Compressibility Error, which is caused by air becoming compressed in the Pitot Tube.
CAS ± Density Error + Compressibility Error = TAS

21. Units of Time
Time is probably the only example of scientific measurement where every nation uses the same units.
Everyone is familiar with days, hours and minutes; it is only necessary to ensure that you use hours when working with knots as this speed is nautical miles per hour.

22. Units of Time
In military and commercial aviation the 24 hour clock is used, set to Greenwich Mean Time GMT or Coordinated Universal Time (UTC) as it is now known.
UTC can also be known as Zulu Time
Summer Time or Daylight Saving Time is always ignored.
UTC can also be known as Zulu Time
The above link will give reference to the variety of time zones:
Zulu
Yankee
X-ray
Whiskey
Victor
Uniform
Tango
Sierra
Romeo

23. Calculation of Time of Flight (Still Air)
If a car travels 120 miles at 60 mph, it will take 2 hours to complete the journey.
This is calculated using the distance speed time formulae

24. Provided 2 quantities are known
From Speed Distance and Time
The 3rd one can be calculated using the
following formula

25. Calculation Triangle (Still Air)
Speed
Time
Distance

26. DISTANCE (D)
TIME(T)
SPEED (S) =
DISTANCE (D)
SPEED (S)
TIME (T) =
DISTANCE =
SPEED (S) x TIME (T)

27. How fast must we go to cover
Example:
How fast must we go to cover
1500 nm in 5 hours?
Quantities known are:
Distance
Time

28. Therefore we use the following formulae:
DISTANCE (D)
TIME(T)
SPEED (S) =
Therefore: 3
1500 nm
S (Knots) = =
300
5 hours 1

29. Check of Understanding
One degree of latitude represents:
1 nm
6 nm
60 nm
360 nm

30. 450 nm 525 nm 275 nm 325 nm Glasgow is due north of Plymouth
(approximately on the same meridian).
If Glasgow is latitude 55°50’ and
Plymouth is latitude 50°25’
what distance are the two places apart?:
525 nm
450 nm
275 nm
325 nm

31. 55° 50’ -
50° 25’
55 – 50 = 5
5 x 60 = 300
50 – 25 = 25
= 325nm

32. In the RAF, aircraft speeds are
generally expressed in:
metres per second
miles per hour
nautical miles per second
Knots

33. An ASI has an instrument correction factor of
+3 kts and a pressure correction factor of -1 Kts.
If the instrument reads 130 kts what is the CAS?
130 Kts
132 Kts
133 Kts
134 Kts

34. IAS ± Pressure Error ± Instrument Error = CAS
130 kts + 3 kts – 1 kts = CAS
133 kts – 1 kts = CAS
132 kts = CAS

35. A Tornado is flying at a TAS of 400 kts.
How far will it travel in 2 hrs?
200 nm
200 Km
800 nm
800 Km

36. DISTANCE =
SPEED (S) x TIME (T)
D = 400 kts x 2 hrs
D = 400 x 2 = 800
Kts = Nautical Miles per hour
800 Nautical Miles
800 nm