Which component allows an autorotation in engine failure?

Which component allows an autorotation in engine failure?

• A. Hydraulic pump
• B. Tail rotor gearbox
• C. Freewheeling Unit
• D. Primary rotor blades

Answer: (C)

Autorotation relies on the rotor being driven by aerodynamic lift rather than by engine torque. To make that possible when power is lost, the drivetrain must be decoupled from the engine. The Freewheeling Unit does exactly that: it disengages the engine from the main rotor so the rotor can continue turning freely as air moves through the blades during a descent. When power is available, the unit locks and the engine drives the rotor; when power is lost, it frees the rotor to windmill and be controlled by rotor blade pitch to land safely. The other components don’t enable autorotation: the hydraulic pump powers hydraulics, not rotor motion; the tail rotor gearbox handles the tail rotor drive, not the main-rotor decoupling; and the blades themselves can rotate, but autorotation is made possible by the drivetrain decoupling provided by the Freewheeling Unit.

Autorotation relies on the rotor being driven by aerodynamic lift rather than by engine torque. To make that possible when power is lost, the drivetrain must be decoupled from the engine. The Freewheeling Unit does exactly that: it disengages the engine from the main rotor so the rotor can continue turning freely as air moves through the blades during a descent. When power is available, the unit locks and the engine drives the rotor; when power is lost, it frees the rotor to windmill and be controlled by rotor blade pitch to land safely. The other components don’t enable autorotation: the hydraulic pump powers hydraulics, not rotor motion; the tail rotor gearbox handles the tail rotor drive, not the main-rotor decoupling; and the blades themselves can rotate, but autorotation is made possible by the drivetrain decoupling provided by the Freewheeling Unit.