In hover, the power required to hover is typically less than out of ground effect.

In hover, the power required to hover is typically less than out of ground effect.

• A. In ground effect, the power required to hover is typically less than out of ground effect
• B. In ground effect, the power required to hover is typically greater than out of ground effect
• C. In ground effect, the power required to hover is the same as out of ground effect
• D. Ground effect has no impact on hover power

Answer: (A)

Ground effect changes the rotor wake in a way that makes hovering more efficient near the surface. In hover, most of the power goes into producing the downward induced velocity to balance weight. When the rotor is close to the ground, the upflow is restrained and the flows from the rotor interact with the ground (like an image rotor), increasing lift efficiency. This reduces the induced velocity needed for the same thrust, so the induced power drops. As you move away from the surface, that interference fades and hover power rises toward the free-space value. So hovering near the ground typically requires less power than hovering out of ground effect.

Ground effect changes the rotor wake in a way that makes hovering more efficient near the surface. In hover, most of the power goes into producing the downward induced velocity to balance weight. When the rotor is close to the ground, the upflow is restrained and the flows from the rotor interact with the ground (like an image rotor), increasing lift efficiency. This reduces the induced velocity needed for the same thrust, so the induced power drops. As you move away from the surface, that interference fades and hover power rises toward the free-space value. So hovering near the ground typically requires less power than hovering out of ground effect.