Automatic prop synchronization on most reciprocating multi-engine aircraft is accomplished by which mechanism?

• A. By electronically controlled fuel metering
• B. By adjusting engine RPM via throttle friction
• C. Through external hydraulic servo
• D. Through the actuation of the propeller governors

Answer: (D)

Automatic prop synchronization is achieved by the actuation of the propeller governors. Each constant-speed propeller is driven by a governor that senses engine RPM and adjusts blade pitch via a hydraulic actuator to hold a chosen speed. When multiple engines are linked, the governors influence each other so both propellers settle at the same RPM and share load evenly. If one engine tends to speed up or slow down, the interlinked governors adjust pitch to bring the RPMs into harmony. This mechanism is what makes synchronization work; other options describe different systems (fuel metering, throttle friction, or an external hydraulic servo) that don’t directly govern and synchronize prop RPM across engines.