When an aeroplane leaves ground effect while maintaining a constant angle of attack, which statement is true?

• A. The lift coefficient remains constant.
• B. The induced drag coefficient increases.
• C. The lift coefficient increases.
• D. The induced drag coefficient decreases.

Answer: (B)

Leaving ground effect changes how the wing interacts with its own trailing vortices. When close to the surface, the ground interferes with the wingtip vortices and downwash, reducing the energy lost to those vortices. As you move away from the ground, that interference diminishes and the downwash rises toward the free-air value, so more energy goes into producing the wing’s lift via the vortices. For the same angle of attack, this means the induced drag increases as you leave ground effect. Lift coefficient for a fixed angle of attack isn’t perfectly constant during this transition, but the key point here is that induced drag rises when you leave ground effect.