In steady flight, the airspeed that yields maximum glide range is associated with which condition?

In steady flight, the airspeed that yields maximum glide range is associated with which condition?

• A. Maximum lift
• B. Minimum speed
• C. Maximum lift-to-drag ratio
• D. Maximum thrust

Answer: (C)

In steady, unpowered flight the distance you can glide forward for a given loss of altitude is tied to the glide ratio. Since lift must balance weight in a glide, lift equals weight, so the glide ratio equals W divided by drag (L/D = W/D). Maximizing glide range means maximizing L/D, i.e., minimizing the drag for the lift you need. The speed that achieves the largest L/D is the airspeed for maximum lift-to-drag ratio. At that speed the combination of induced drag and parasite drag is most favorable for the required lift, giving the greatest forward distance per unit of altitude lost. That’s why the best choice is the condition of maximum lift-to-drag ratio. The other options lead to more drag for the needed lift or are irrelevant in a glide (thrust).

In steady, unpowered flight the distance you can glide forward for a given loss of altitude is tied to the glide ratio. Since lift must balance weight in a glide, lift equals weight, so the glide ratio equals W divided by drag (L/D = W/D). Maximizing glide range means maximizing L/D, i.e., minimizing the drag for the lift you need. The speed that achieves the largest L/D is the airspeed for maximum lift-to-drag ratio. At that speed the combination of induced drag and parasite drag is most favorable for the required lift, giving the greatest forward distance per unit of altitude lost.

That’s why the best choice is the condition of maximum lift-to-drag ratio. The other options lead to more drag for the needed lift or are irrelevant in a glide (thrust).