A helicopter is equipped with a governor system that automatically adjusts engine throttle to maintain rotor RPM as collective pitch changes. During a rapid collective increase, the pilot notices the governor briefly lags before RPM stabilizes at the correct value. What is the correlator/throttle system's primary function in this design?
- ATo disengage the engine from the rotor system in the event of an engine failure
- BTo transmit cyclic control inputs to the swashplate for pitch changes
- CTo limit maximum rotor RPM during autorotation to prevent overspeed
- DTo automatically maintain a nearly constant rotor RPM by adjusting throttle in response to collective pitch changes
Show answer & explanationAnswer & explanation
Correct answer: D. To automatically maintain a nearly constant rotor RPM by adjusting throttle in response to collective pitch changes
A correlator (mechanical, linking throttle to collective) or governor (electronic/hydromechanical, sensing RPM) automatically adjusts engine power/throttle as the collective is raised or lowered, keeping rotor RPM nearly constant so the pilot does not need to manually twist the throttle for every collective change, though fine-tuning may still be needed with a correlator.
Why the other options are wrong
- A. Engine disconnection during failure is the job of the freewheeling unit, not the governor/correlator.
- B. Cyclic inputs are transmitted through the swashplate directly, not through the throttle correlator/governor.
- C. Rotor RPM limiting during autorotation is managed by pilot collective control, not by the throttle correlator/governor, since the engine is disconnected.
Throttle Correlator / Governor
A mechanical linkage (correlator) or automatic sensing system (governor) that adjusts engine throttle as collective pitch is changed, to maintain a relatively constant main rotor RPM.
- Correlator is a mechanical linkage requiring some pilot throttle correction
- Governor senses RPM electronically/hydromechanically and adjusts automatically with little pilot input
- Both reduce pilot workload but differ in precision and response
Memory trick: Correlator/governor: the 'autopilot' for keeping rotor RPM steady as collective moves.