Which components control rotor rpm and how is it maintained during power changes?

Which components control rotor rpm and how is it maintained during power changes?

• A. The autopilot system and engine fuel flow; autopilot maintains rpm via throttle.
• B. The governor and flight control linkage; the governor adjusts collective to maintain target rpm while monitoring Nf/Nr.
• C. The transmission gear ratio only; rotor rpm is fixed by gearing.
• D. The pilot's cyclic input solely; rotor rpm is not actively controlled.

Answer: (B)

Rotor speed is actively kept at a set value by the governor working through the flight control linkage. The pilot’s collective input sets the desired blade pitch and load, but the actual rotor rpm is held steady by a closed-loop system: the governor watches the rotor speeds (Nr, and related engine speed references) and automatically adjusts power delivery and, via the flight control linkage, the collective to keep Nr at the target. When power changes occur—such as increasing collective to lift more—the rotor load rises and Nr tends to drop; the governor responds by increasing engine power (and, through the linkage, modulating collective pitch) to restore the rotor speed. Conversely, if power is reduced and the rotor tends to accelerate, the governor reduces power and/or adjusts the collective to bring Nr back to the setpoint. The autopilot or fixed gearing don’t regulate rotor speed by themselves, and the control input from the cyclic alone doesn’t actively regulate rotor rpm, so the governor paired with the flight control linkage is the correct mechanism.

Rotor speed is actively kept at a set value by the governor working through the flight control linkage. The pilot’s collective input sets the desired blade pitch and load, but the actual rotor rpm is held steady by a closed-loop system: the governor watches the rotor speeds (Nr, and related engine speed references) and automatically adjusts power delivery and, via the flight control linkage, the collective to keep Nr at the target. When power changes occur—such as increasing collective to lift more—the rotor load rises and Nr tends to drop; the governor responds by increasing engine power (and, through the linkage, modulating collective pitch) to restore the rotor speed. Conversely, if power is reduced and the rotor tends to accelerate, the governor reduces power and/or adjusts the collective to bring Nr back to the setpoint. The autopilot or fixed gearing don’t regulate rotor speed by themselves, and the control input from the cyclic alone doesn’t actively regulate rotor rpm, so the governor paired with the flight control linkage is the correct mechanism.