Which factor is listed as causing loss or apparent loss of ground effect?

• A. Beginning of translational movement
• B. Altitude greater than two rotor diameters
• C. Hovering into a wind
• D. Tall grass and bushes

Answer: (A)

Ground effect is the cushion the rotor produces when its downwash is close to the surface, with the ground reflecting some of that flow back up and increasing lift efficiency. When you begin translating from a hover, the rotor wash starts moving forward and the ground’s reflection no longer interacts with the rotor inflow in the same way. The downwash becomes less confined, the induced velocity at the rotor increases, and more power is needed to maintain the same altitude—so you experience an apparent loss of ground effect. This transition is the moment most pilots notice the effect, which is why beginning translational movement is listed as causing loss or apparent loss of ground effect. Being higher than about a rotor diameter removes ground effect regardless of motion, hover wind simply shifts the inflow a bit, and tall grass or bushes don’t change the fundamental near-ground flow in the same way.