What is best glide speed and when is it used?

• A. The speed giving the minimum sink rate; used during engine-off flight to maximize altitude.
• B. The speed that minimizes drag in level flight; used to conserve fuel.
• C. The speed at which the airplane can turn most steeply.
• D. The speed giving the maximum glide distance; used during an engine failure for a safe forced landing.

Answer: (D)

Best glide speed is the airspeed at which the airplane achieves its maximum lift-to-drag ratio, giving the greatest forward distance for a given loss of altitude. This is the speed you want in an engine-out situation because it lets you cover the most ground before you must land, increasing the chances of reaching a suitable landing area. In practice, you fly this speed with the airplane in its clean configuration (flaps up) and adjust for wind to optimize glide distance to a chosen landing spot. The other speeds describe different goals—minimum sink rate aims to stay aloft longer but reduces distance; minimum-drag in level flight is about powered cruise efficiency; and turning capability is unrelated to maximizing glide distance.