AFH 3-22

The best glide airspeed is used to maximize the distance flown. This airspeed is important when a pilot is attempting to fly during an engine failure. The best airspeed for gliding is one at which the airplane travels the greatest forward distance for a given loss of altitude in still air. This best glide airspeed occurs at the highest lift-to-drag ratio (L/D). [Figure 3-23] When gliding at airspeed above or below the best glide airspeed, drag increases. Any change in the gliding airspeed results in a proportional change in the distance flown. [Figure 3-24] As the glide airspeed is increased or decreased from the best glide airspeed, the glide ratio is lessened. Figure 3-23. L/DMAX. Figure 3-24. Best glide speed provides the greatest forward distance