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Old 8th February 2008 | 14:55
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IO540
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From: EuroGA.org
The only one I use is

VS (feet/min) = 200 x height to lose in 1000s of feet (at 10nm to run, 120kt)

e.g. if at 5000ft and need to descend to 2000ft, VS= 200x3 = -600fpm

OTOH if one has 20nm to run, one needs only -300fpm.

Everything else comes from the GPS.

Up to 150 kts WCA (Wind Correction Angle)= 1/2 x windspeed.
Your max drift or max correction angle is half the windspeed.
Above 150 kts it's 1/3.
Check it with your CRP, it's surprisingly accurate.
The above is very good - one of the best ever. One of the great secrets (never mentioned in PPL training) is that the winds aloft forecasts are usually so far out that there is little point in using the circular slide rule - these simple rules of thumb are just as good.
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