Define autorotation.

Define autorotation.

• A. An event in which no engine power is supplied, and the main rotor is driven by relative wind only
• B. An event during which engine power is continuously supplied to the rotor to maintain RPM
• C. A maneuver used to maintain rotor speed while descending vertically
• D. A procedure to restart the engine during autorotation

Answer: (A)

Autorotation is the state in which the main rotor is driven by the upward flow of air through the rotor disc, not by the engine. When engine power is removed (or the rotor is decoupled by a freewheel), air moving upward as the aircraft descends causes the rotor to continue turning. The pilot then uses collective and descent control to manage rotor speed and energy, allowing a safe landing without engine power. This distinguishes it from powered flight, where engine power drives the rotor, and from a restart procedure, which is about re-engaging power rather than defining the rotor’s mode of operation. It’s also broader than a strict vertical descent—the key point is that the rotor is driven by relative wind, not by the engine.

Autorotation is the state in which the main rotor is driven by the upward flow of air through the rotor disc, not by the engine. When engine power is removed (or the rotor is decoupled by a freewheel), air moving upward as the aircraft descends causes the rotor to continue turning. The pilot then uses collective and descent control to manage rotor speed and energy, allowing a safe landing without engine power.

This distinguishes it from powered flight, where engine power drives the rotor, and from a restart procedure, which is about re-engaging power rather than defining the rotor’s mode of operation. It’s also broader than a strict vertical descent—the key point is that the rotor is driven by relative wind, not by the engine.