What is the best-glide speed used for engine-out procedures?

• A. The speed that yields maximum rate of climb.
• B. The minimum controllable airspeed.
• C. The speed for maximum lift-to-drag ratio.
• D. The stall speed plus 10 knots.

Answer: (C)

In an engine-out glide, you aim to maximize the distance you can cover for the altitude you have, so you choose the speed that yields the best lift-to-drag ratio. This is the best-glide speed. At this point, the aircraft descends with the smallest angle for a given weight, meaning you get the greatest glide range and the longest possible distance before landing. Drag increases more quickly if you go faster, and you lose lift efficiency if you go slower toward stall, so there’s little to gain outside this sweet spot.

Other options don’t maximize glide distance. The speed for maximum rate of climb applies to powered, climbing flight and doesn’t optimize endurance in a glide. The minimum controllable airspeed is near stall and unsafe for maneuvering or energy management. Stall speed plus a small margin is a safe operating buffer but does not provide the longest possible glide distance.