- Calculate altitude to lose: Current Altitude - Landing Pattern Altitude (1000 above ground lvl usually used): Cruise altitude: 10000ft. Airport altitude: 200ft. 10000 - 1200 = 8800
- Calculate time: Altitude to lose - Descent speed (500-1000) in FPM. 8800 / 500fpm = 18m
- Calculate distance from AP to start descending: Time to descend * AP.
// Air Speed
60 knots = 1 NM/min
90 knots = 1.5 NM/min