Which term refers to the force reduction in rotor-induced drag when operating close to the ground?

Which term refers to the force reduction in rotor-induced drag when operating close to the ground?

• A. Ground Effect
• B. Ground Resonance
• C. Induced Drag
• D. Translational Lift

Answer: (A)

Ground effect is the phenomenon where rotor downwash is impeded by the ground, creating a cushion of air that reduces the induced velocity and the power needed to generate lift. This means rotor-induced drag decreases when the helicopter is very close to the surface, making flight more efficient near the ground. The effect is strongest within about one rotor diameter of the ground and fades as you climb away. Translational lift is about forward airspeed improving lift, ground resonance is a vibration condition on the ground, and induced drag is the drag from producing lift but not specifically the proximity to the surface.

Ground effect is the phenomenon where rotor downwash is impeded by the ground, creating a cushion of air that reduces the induced velocity and the power needed to generate lift. This means rotor-induced drag decreases when the helicopter is very close to the surface, making flight more efficient near the ground. The effect is strongest within about one rotor diameter of the ground and fades as you climb away. Translational lift is about forward airspeed improving lift, ground resonance is a vibration condition on the ground, and induced drag is the drag from producing lift but not specifically the proximity to the surface.