The rotor brake system is used to stop rotor rotation.

• A. Main Transmission
• B. Mast Moment Indicator
• C. Rotor Brake System
• D. Freewheeling Unit

Answer: (C)

The rotor brake system is designed to stop rotor rotation by applying controlled friction to the rotor, bringing it to a halt after engine shutdown or for maintenance and secure parking. This prevents windmilling and keeps the rotor from moving unexpectedly in wind or while being worked on. The main transmission carries engine power to the rotor and isn’t used to stop rotation on command. The freewheeling unit allows the rotor to continue spinning freely (or decouple the engine) when the engine isn’t driving the rotor, so it doesn’t brake rotation. The mast moment indicator monitors torque on the rotor mast to assess loading, not to stop rotation. So the rotor brake system is the component specifically built to stop rotor rotation.