Compared with out of ground effect, in-ground-effect at the same angle of attack yields what change in lift and induced drag?

Compared with out of ground effect, in-ground-effect at the same angle of attack yields what change in lift and induced drag?

• A. Lift decreases and induced drag increases
• B. Lift remains the same and induced drag remains the same
• C. Lift increases and induced drag decreases
• D. Lift increases and induced drag increases

Answer: (C)

In ground effect, the ground plane interferes with the wing’s wake, changing how the air circulates around the wing. Being close to the surface reduces the downwash behind the wing and suppresses part of the wingtip vortices. With less downwash, the wing behaves as if the flow is closer to the wing’s ideal condition for lift, so for the same angle of attack the wing can generate more lift. At the same time, those vortices are weaker and more confined, which reduces the induced drag that comes from producing that lift. So, near the ground, lift increases and induced drag decreases at the same angle of attack (an effect that fades as you climb higher and leave ground effect).

In ground effect, the ground plane interferes with the wing’s wake, changing how the air circulates around the wing. Being close to the surface reduces the downwash behind the wing and suppresses part of the wingtip vortices. With less downwash, the wing behaves as if the flow is closer to the wing’s ideal condition for lift, so for the same angle of attack the wing can generate more lift. At the same time, those vortices are weaker and more confined, which reduces the induced drag that comes from producing that lift. So, near the ground, lift increases and induced drag decreases at the same angle of attack (an effect that fades as you climb higher and leave ground effect).