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[Coke611]

Was reading Holloway's post about radio & navigation a moment ago, and wondered, how can you tell how far you are from a certain point by just using a stopwatch? Probably seems like a silly question for you qualified folks but for a low hour student PPL like me, its a mystery!


I train in a C152, so, how do I know how far I have travelled in a certain time etc?

Cheers

Louis Coke (Coke611)

[Lawyerboy]

All down to maths (not my strong point) and depends on the wind, but the easiest way I've found of doing it is basically...

Imagine you're flying in a straight line at 100kt per hour. It would take you 6 minutes to travel 10 nautical miles (100kt in an hour, divide an hour by 10 and you get 6 minutes, divide 100 by 10 you get 10, therefore 10 miles in 6 minutes). From that starting point you can work out pretty much anything else you need.

For example, you're travelling at 85kt and there's a 10kt headwind. Your groundspeed (the speed at which you're covering the ground) is 75kt. You're therefore doing 7.5 miles in 6 minutes, so if you know you've been flying for, say, 18 minutes you know you've probably covered about 22.5 miles.

No doubt others will have their own method.

LB.

[Just_Another_PPL]

I dont know how far through your trainnig you are, but have you been introduced to a "whizzwheel" flight computer? If you have work out your Groundspeed using the wind side then put this speed at the top of the wheel then look at the time you want, say 22 mins then read of how far you have gone.

If you havent well, Distance = Speed x Time, the only problem will be working out your groundspeed, i would wait till you are taught to use the computer.

[Lawyerboy]

Only one thing about the whizzwheel, JAP - ain't always there when you need it, nor is it always all that convenient to use it when it is. As much as it's a pain, you really ought to be able to do some basic calculations in your head, Coke old chap, particularly if you need to divert.

[Just_Another_PPL]

Yes but before you go off on a flight you should have the winds aloft and so you can work out the effect the winds will have very quickly, there are many ways of doing this that are quick (thus usefull during diversions) and after all when you are dealling with 90 kts 2 knots calculation error wont make much diffrence.

[Lawyerboy]

Sorry, think I caught the wrong end of the stick - didn't mean to suggest you do all your preflight stuff in your head! Good grief, I'd be there for hours....

[Just_Another_PPL]

HAHA, i can imagine that now, working out Leg-times and the such whilst doing the preflight :)