Which statement about ground effect is correct?

• A. The downwash angle remains constant
• B. The induced angle of attack decreases
• C. The lift coefficient decreases
• D. The airspeed increases

Answer: (B)

Ground effect happens when the wing is close to the surface, and the ground interferes with the wing’s wingtip vortices. This interference reduces the downward deflection of the airflow produced by the wing, so the induced component of the flow—often described as the induced angle of attack—becomes smaller. With less induced flow acting on the wing, the effective angle at which the wing meets the air due to induced effects is reduced, which increases lift for a given pitch and reduces induced drag. That’s why the statement that the induced angle of attack decreases is the correct description. The other ideas aren’t right: the downwash changes as you near the ground, lift coefficient actually tends to increase (not decrease) for a given angle of attack, and airspeed isn’t inherently increased by ground effect.