The rotor brake should never be applied under which condition?

The rotor brake should never be applied under which condition?

• A. With NR above 76%
• B. When the helicopter is in a hover
• C. During engine start
• D. With rotor speed below 60%

Answer: (A)

The rotor brake is meant to stop the main rotor when the helicopter is on the ground with power off, not to be used while the rotor is still turning fast. Engaging it when the rotor is turning at a high speed loads the brake and the drivetrain with a large amount of kinetic energy to dissipate all at once. That sudden, high braking torque can overstress the rotor system, gearbox, and brake components, risking damage. Because of that, you should never apply the rotor brake when rotor speed is high—specifically when NR is above 76%. If you need to use the brake, wait until NR has decayed to a much lower, safe level (well below the high RPM range), then engage it to finish stopping the rotor.

The rotor brake is meant to stop the main rotor when the helicopter is on the ground with power off, not to be used while the rotor is still turning fast. Engaging it when the rotor is turning at a high speed loads the brake and the drivetrain with a large amount of kinetic energy to dissipate all at once. That sudden, high braking torque can overstress the rotor system, gearbox, and brake components, risking damage.

Because of that, you should never apply the rotor brake when rotor speed is high—specifically when NR is above 76%. If you need to use the brake, wait until NR has decayed to a much lower, safe level (well below the high RPM range), then engage it to finish stopping the rotor.