Which component automatically disconnects the main rotor from the engine when the engine slows below rotor RPM?

Which component automatically disconnects the main rotor from the engine when the engine slows below rotor RPM?

• A. Freewheeling Unit
• B. Coupler
• C. Clutch
• D. Brake

Answer: (A)

A one-way decoupling device is designed to automatically disconnect the engine from the rotor when the rotor is turning faster than the engine. This is the freewheeling unit. It allows the rotor to continue spinning in an autorotation even if the engine slows or fails, without forcing the engine to wind up or drag the rotor. When the engine speed remains higher than rotor speed, the unit locks and the engine drives the rotor; but if the rotor tries to wind down the engine, the mechanism disengages, letting the rotor freewheel. This prevents engine damage and reduces drag during low engine RPM or engine failure, which is essential for safe autorotation. The other components aren’t designed to automatically provide this decoupling: a coupler is meant to connect the engine and rotor, a clutch engages/disengages under control, and a brake slows or stops motion rather than enabling independent rotor motion.

A one-way decoupling device is designed to automatically disconnect the engine from the rotor when the rotor is turning faster than the engine. This is the freewheeling unit. It allows the rotor to continue spinning in an autorotation even if the engine slows or fails, without forcing the engine to wind up or drag the rotor. When the engine speed remains higher than rotor speed, the unit locks and the engine drives the rotor; but if the rotor tries to wind down the engine, the mechanism disengages, letting the rotor freewheel. This prevents engine damage and reduces drag during low engine RPM or engine failure, which is essential for safe autorotation. The other components aren’t designed to automatically provide this decoupling: a coupler is meant to connect the engine and rotor, a clutch engages/disengages under control, and a brake slows or stops motion rather than enabling independent rotor motion.