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AIR NAVIGATION

AIR NAVIGATION. Part 4 Magic Numbers. Introduction. So far we have talked about drawing vectors on paper. This is fine in the office or the classroom but impossible in the confines of a small aircraft. Introduction. So for many years, navigators have been using

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AIR NAVIGATION

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  1. AIR NAVIGATION

    Part 4 Magic Numbers
  2. Introduction So far we have talked about drawing vectors on paper. This is fine in the office or the classroom but impossible in the confines of a small aircraft.
  3. Introduction So for many years, navigators have been using the Dalton hand held computer, and these are still used in the private flying world.
  4. Introduction The fast jet navigator in the RAF solves the vector triangle using a simplified mental calculation. In civil airliners an onboard computer solves the triangle and many other things besides.
  5. Computers and Numbers All Aircrew have to do a lot of mental arithmetic, even in these days of computers. To aid this Magic Numbers are used. It does not matter if you are flying in a Tutor or a Tornado, the method works equally well.
  6. Computers and Numbers GS nm per min GS nm per min 210 3½ 240 4 300 5 360 6 420 7 480 8 540 9 Magic Numbers are ground speeds in nautical miles per minute. 60 1 80 1⅓ 90 1½ 100 1⅔ 120 2 150 2½ 180 3
  7. Computers and Numbers 120 kts = 2 nm/min Example You are flying at 120 kts GS. You have 20 miles to run before you reach your final destination. How long will this take? Magic Numbers ( 120 divided by 60 ) 20 miles at 2 nm per minute 20 divided by 2 = 10 10 minutes to run
  8. Computers and Numbers 420 kts = 7 nm/min Example You are in a Tornado at low level over Wales doing 420 kts GS. You have 49 miles to run to the next turning point. How long will this take? Magic Numbers ( 420 divided by 60 ) 49 miles at 7 nm per minute 49 divided by 7 = 7 7 minutes to run
  9. Computers and Numbers 5 80 kts = 1⅓ nm/min 3 3 x x 20 20 4 4 4 3 1 Example You are on a cross-country exercise in a Tutor, heading into wind at 80 kts GS. How long will a 20 mile leg take? Magic Numbers ( 80 divided by 60 ) 20 20 mile leg = = 1⅓ 5 x 3 = 15 min =
  10. 6 Minute Magic With the slower speeds it is often easier to think in terms of how far do we go in 6 minutes (1 tenth of an hour). This is simply the ground speed with the last zero removed. Ground Speed 10
  11. 6 Minute Magic So the Tutor doing 80 knots, will travel 8 miles in 6 minutes. Travelling at 110 knots, You go 11 miles in 6 minutes. An aircraft doing 140 knots. will travel 14 miles in 6 minutes.
  12. 6 Minute Magic Despite all the computers, some mental arithmetic is essential, whether you plan to join the RAF as aircrew, become an airline pilot, obtain a PPL, or simply make the most of the available air experience opportunities. The starting point is the 6 times table; no one in their right mind would dream of aviating without this knowledge.
  13. E T A A by-product of solving the Triangle of Velocities is that by making the DST calculation using Ground Speed and Distance To Go, we can calculate the time that it will take to reach the next turning point or destination. This time is called Estimated Time of Arrival (ETA)
  14. E T A The Estimated Time of Arrival (ETA) is important both for fuel calculations and for Air Traffic control purposes. A particular application of this is the ETA for the destination. If you do not arrive on time, Air Traffic will have to take overdue action; similar to a search party going out to find a group of walkers who have not returned from a trek on time.
  15. Check Understanding What is the name of the hand held computer still used by navigators in private flying? Dalton Newton Dawson Nelson
  16. Check Understanding Flying at 240 kts ground speed, how long will it take to cover 40 nm ? 2 mins 6 mins 10 mins 20 mins
  17. Check Understanding While flying you cover 3 nm every minute, What is your ground speed? 120 kts 150 kts 180 kts 210 kts
  18. Check Understanding In a Tutor doing 80 knots, how far will you travel in 6 minutes? 6 nm 8 nm 10 nm 13⅓ nm
  19. Check Understanding Estimated Time of Arrival is important. ETA calculations help the crew to determine . . . Fuel calculations The shortest route Drift corrections Wind speed and direction
  20. Check Understanding An aircraft does not arrive at its destination on its ETA, What action will Air Traffic Control take? No immediate action Close down Initiate overdue action Contact the departure base

  21. AIR NAVIGATION

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