Glider Instructor Practice Test

Best glide is found at the speed that yields the highest lift-to-drag ratio. The L/D ratio tells you how far you can travel horizontally for each unit of altitude you lose during unpowered flight. When you reach the speed where this ratio is最大, drag is minimized relative to the lift, so you cover the most ground for a given descent.

For typical training gliders, that maximum efficiency is around twenty-to-one. In other words, you can expect about twenty units of forward distance for every unit of altitude lost, assuming still air and flight in steady conditions. That’s why the option describing twenty-to-one is the best choice.

Keep in mind that wind, weight, and sailplane design can shift the exact value, but twenty-to-one is the standard practical figure used for teaching best-glide performance.