During power changes, which instruments are used to monitor rotor speed?

During power changes, which instruments are used to monitor rotor speed?

• A. Altimeter and airspeed.
• B. Fuel flow and oil temperature.
• C. Nf and Nr instruments.
• D. Compass and VSI.

Answer: (C)

During power changes you need to watch both the rotor and engine speeds. The rotor speed indicator (Nr) shows how fast the main rotor is turning, while the engine/gas generator speed indicator (Nf) shows the speed driving the power turbine that ultimately feeds the rotor. Keeping an eye on Nr ensures the rotor stays within safe RPM limits, and monitoring Nf ensures the engine is delivering the expected power and responding properly to changes. The other instruments measure altitude, airspeed, fuel flow, oil temp, heading, or vertical speed, which don’t directly reflect rotor speed.

During power changes you need to watch both the rotor and engine speeds. The rotor speed indicator (Nr) shows how fast the main rotor is turning, while the engine/gas generator speed indicator (Nf) shows the speed driving the power turbine that ultimately feeds the rotor. Keeping an eye on Nr ensures the rotor stays within safe RPM limits, and monitoring Nf ensures the engine is delivering the expected power and responding properly to changes. The other instruments measure altitude, airspeed, fuel flow, oil temp, heading, or vertical speed, which don’t directly reflect rotor speed.