What is the required separation for a hovering helicopter?

The separation required for a hovering helicopter is based on the principle of avoiding interference between the rotor downwash and other nearby aircraft or obstacles. The correct answer identifies three rotor diameters as the necessary separation distance because this distance ensures that the helicopter's rotor wash does not significantly affect nearby structures or aircraft, thereby minimizing turbulence effects and ensuring stable hovering conditions.

When a helicopter hovers, it generates a downward flow of air as its rotor blades spin. This downwash can cause turbulence and instability for other aircraft, especially if they are too close. Three rotor diameters is generally considered a safe distance to allow for the dispersal of the downwash and prevent any harmful interference with nearby entities. By adhering to this separation guideline, pilots can ensure a safer operating environment in busy airspaces or near ground obstacles.