On completion of this presentation, you should be able to carry out calculations to determine aircraft distance, speed, and time.

1. 1
Introduction to Dead
Reckoning Navigation
Measuring Tracks and Distance
Part 1.

2. Learning Outcome
2
On completion of this unit, you should be
able to carry out calculations to determine
aircraft distance, speed, and time.

3. 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
3

4. Circumference of The
Earth
• As a complete
circle is 360°
• then 360 x 60
gives the
circumference of
the Earth as
21600 nm
4

5. Latitude & Longitude
• 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”
5

6. Lat/Long Grid Line
6

7. Coordinate Structure
Latitude first, followed by longitude
7

8. Finding Distance Between 2 Points
• 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?
8

9. 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
9

10. Aircraft Speed
• The speed for cars, motorcycles and other land-based
vehicles:
Miles per hour, or Kilometers per hour
• For aircraft, the speed is a measure of:
Nautical Miles per hour – (Knots)
10

11. 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)
11

12. Aircraft Speed
• ASI measures the
dynamic air
pressure
• Dynamic Air
Pressure is the
pressure caused by
forward motion of
the aircraft
12

13. Aircraft Speed
13

14. Aircraft Speed
14

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

16. Pitot Tube Position
Light Aircraft Medium or Heavy Aircraft
16

17. 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.
17

18. 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.
18

19. Calculation of Flight Time
• 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 formula
19

20. Calculation of
Flight Time
Provided 2 quantities are
known from “Speed
Distance and Time”, The
3rd one can be
calculated using the
following formula:
20

21. Calculation of Flight Time
Example:
How fast must we go to cover 1500 nm in 5
hours?
21

22. Example:
How fast must we go to cover 1500 nm in 5
hours?
22
Calculation of Flight Time

23. We use the following formula:
23
Calculation of Flight Time
Speed (S) =
Distance (D)
Time (T)
Speed (S) =
1500
5
Speed (S) = 300 Knots

24. 24
END OF PART 1