Which wing characteristic most directly affects glide efficiency when power is off?

• A. Planform shape
• B. Wing sweep
• C. Aspect ratio
• D. Fuselage length

Answer: (C)

Glide efficiency when power is off is basically about how far you can fly for a given amount of lift and drag, i.e., the lift-to-drag ratio. The wing characteristic that most directly improves this ratio is the aspect ratio—the wingspan squared divided by the wing area. A higher aspect ratio means less induced drag for the same lift, because the wing produces lift more efficiently with less energy lost to wingtip vortices. That reduction in induced drag raises the overall L/D, giving a better glide ratio and longer distance flown without power.

Planform shape does influence induced drag, and an efficient distribution of lift helps, but aspect ratio is the primary factor that governs glide efficiency. Wing sweep can actually increase induced drag at lower speeds and isn’t beneficial for unpowered glide in the same way. Fuselage length affects overall drag and stability more than it directly changes the wing’s glide efficiency.