How does an autorotation maneuver work?

An autorotation maneuver is a vital technique used in helicopter flight to manage a controlled descent without the use of engine power. During this maneuver, if engine power is lost or reduced, the pilot can enter autorotation by lowering the collective pitch, which allows the helicopter to descend while maintaining rotor speed. This occurs because the rotor blades continue to receive lift from the upward flow of air entering the rotor system as the helicopter descends.

The ability to control the descent in this way is crucial for safely landing a helicopter in emergency situations where engine power is not available. The pilot can manage the descent rate and make a controlled landing by manipulating the collective and cyclic controls as needed. This skill is essential for pilots, as it ensures safety and minimizes the risk of a crash when faced with engine failure.

In contrast, the other choices do not accurately describe the autorotation process and its purpose within helicopter operations. Autorotation does not serve to gain altitude, increase fuel efficiency, or maintain hover stability. Instead, it is a specific emergency landing technique critical for helicopter safety.