What is ground effect in relation to helicopter performance?

Ground effect refers to the increased efficiency and performance of a helicopter when it operates close to the ground, typically within one rotor diameter of the surface. In this proximity, the airflow patterns around the rotor blades are altered positively, resulting in an increase in lift and a reduction in the power required to maintain a hover. This is due to the fact that the rotor blades operate in a more compressed air environment, which enhances lift and reduces the induced drag.

While hovering, the helicopter benefits from this phenomenon because the ground acts as a barrier to the downward-moving air, effectively 'cushioning' the rotor blades and allowing them to produce more lift with less power input. Therefore, the correct interpretation of ground effect in relation to helicopter performance is encapsulated in the option regarding increased performance while hovering. This characteristic is critically important for pilots to understand, as it can significantly influence operational capabilities, especially in low-altitude operations.