Hovering a distance greater than one disk diameter above the surface describes which hover state?

Hovering a distance greater than one disk diameter above the surface describes which hover state?

• A. In Ground Effect Hover
• B. Out of Ground Effect Hover
• C. Hover at Surface
• D. Grounded Hover

Answer: (B)

The main idea here is how proximity to the surface changes hover efficiency. When a helicopter is within about one rotor diameter above the ground, the downwash is reflected by the surface and a cushion of air forms under the rotor, reducing induced power and making hover easier. That state is known as in-ground-effect hover. If you’re hovering higher than roughly one rotor diameter above the surface, that ground cushion isn’t present, so you’re out of ground effect. You must generate the same lift with more power because the induced velocity is higher and the hover becomes less efficient. This is the situation described. So hovering a distance greater than one disk diameter above the surface corresponds to an out-of-ground-effect hover. The other terms describe positions closer to the surface or aren’t standard hover states.

The main idea here is how proximity to the surface changes hover efficiency. When a helicopter is within about one rotor diameter above the ground, the downwash is reflected by the surface and a cushion of air forms under the rotor, reducing induced power and making hover easier. That state is known as in-ground-effect hover.

If you’re hovering higher than roughly one rotor diameter above the surface, that ground cushion isn’t present, so you’re out of ground effect. You must generate the same lift with more power because the induced velocity is higher and the hover becomes less efficient. This is the situation described.

So hovering a distance greater than one disk diameter above the surface corresponds to an out-of-ground-effect hover. The other terms describe positions closer to the surface or aren’t standard hover states.