Ground effect, which affects fixed wing as well as rotary wing aircaft, simply menas the interaction of the downwash from the wing/rotor with the surface cannot be neglected. Once the aircraft is a wing/rotor span or three above the surface, it's "out of ground effect". Closer than that and there is an "air cushion" effect, which effectively translastes into more lift with less power required. A fixed wing would fly at a lower AOA, and have more engine thrust available for accelleration, while the same is true of rotary wing, it's often expressed as the ability to maintain a hover at maximum power. In this case the hover can be maintained at a higher pressure altitude, if the aircraft is hovering near the ground surface (as on a mountain) than if the aircraft were well above the surface.
MM