Adding ballast to a glider affects glide performance by causing what change in required airspeed to maintain the same glide ratio?

Adding ballast to a glider affects glide performance by causing what change in required airspeed to maintain the same glide ratio?

• A. Glide ratio increases with ballast
• B. Glide ratio unchanged with ballast
• C. Ballast reduces stall speed
• D. A higher airspeed is required to obtain the same glide ratio as when lightly loaded

Answer: (D)

The idea being tested is how ballast changes the speed needed to sustain a given glide angle. When a glider takes on ballast, its weight increases, so the wing must generate more lift to balance that weight in a steady glide. Generating more lift at the same airspeed means the wing operates at a higher lift coefficient, which increases induced drag. That extra drag makes the glide steeper and the glide ratio worse at the same speed. To restore the same glide ratio you must fly faster, because increasing airspeed reduces induced drag (and lifts are achieved with a lower angle of attack), while the overall drag changes in a way that allows the same L/D to be reached again. In short, heavier weight raises the speed required to maintain the same glide ratio as when lightly loaded.

The idea being tested is how ballast changes the speed needed to sustain a given glide angle. When a glider takes on ballast, its weight increases, so the wing must generate more lift to balance that weight in a steady glide. Generating more lift at the same airspeed means the wing operates at a higher lift coefficient, which increases induced drag. That extra drag makes the glide steeper and the glide ratio worse at the same speed. To restore the same glide ratio you must fly faster, because increasing airspeed reduces induced drag (and lifts are achieved with a lower angle of attack), while the overall drag changes in a way that allows the same L/D to be reached again. In short, heavier weight raises the speed required to maintain the same glide ratio as when lightly loaded.