The speed at which the lift-to-drag ratio is maximized is commonly referred to as which speed?

• A. Best L/D Speed
• B. Best Climb Speed
• C. Best Stall Speed
• D. Best Landing Speed

Answer: (A)

The main idea is aircraft efficiency expressed as lift-to-drag ratio. Lift-to-drag ratio tells you how much lift you get for every unit of drag. When this ratio is at its highest, the aircraft uses the least amount of drag for the lift it must produce (which, in level flight, equals weight). That means you can travel the farthest horizontally for a given loss of altitude, or fly with the lowest drag for a given lift, making it the most economical speed—hence the name Best L/D speed. It’s the speed at which the airplane delivers the maximum glide range or the best overall efficiency in cruise. The other speeds refer to different performance goals: climb speed optimizes vertical climb rate, stall speed is the minimum speed to maintain controlled flight, and landing speed relates to approach and touchdown, not efficiency.