NR above what percentage is unsafe for rotor brake application?

NR above what percentage is unsafe for rotor brake application?

• A. 76%
• B. 80%
• C. 70%
• D. 90%

Answer: (A)

NR is rotor speed expressed as a percent of the rotor’s maximum speed. The rotor brake is meant to bring the rotor to a stop by dissipating the rotor’s kinetic energy through friction. That energy grows quickly as the rotor spins faster, so there is a limit to how much braking the system can safely absorb. When NR exceeds 76 percent, applying the rotor brake would demand more braking torque and heat than the system is designed to handle, risking excessive loads on the transmission and brake components, and potential damage or unsafe transient forces. Therefore, using the rotor brake when NR is above 76 percent is unsafe. Below that threshold, the brake can be used more safely to stop the rotor.

NR is rotor speed expressed as a percent of the rotor’s maximum speed. The rotor brake is meant to bring the rotor to a stop by dissipating the rotor’s kinetic energy through friction. That energy grows quickly as the rotor spins faster, so there is a limit to how much braking the system can safely absorb. When NR exceeds 76 percent, applying the rotor brake would demand more braking torque and heat than the system is designed to handle, risking excessive loads on the transmission and brake components, and potential damage or unsafe transient forces. Therefore, using the rotor brake when NR is above 76 percent is unsafe. Below that threshold, the brake can be used more safely to stop the rotor.