In propeller synchronization, what is a slave engine?

• A. The engine in a multi-engine airplane whose RPMs follow those set on the master engine.
• B. The engine that has independent RPM control.
• C. The engine that drives the master engine.
• D. A backup engine not used in synchronization.

Answer: (A)

In propeller synchronization, the slave engine is the engine whose RPMs are driven to follow the master engine’s RPM. The master sets the reference speed, and the slave’s throttle/prop governor automatically adjusts to match that speed, so both propellers rotate at the same RPM. This arrangement reduces vibration and helps keep the engines and propellers operating harmoniously.

The other possibilities don’t fit because they describe independent control (not synchronized), driving the master (not the case in a slave), or a backup engine not used in synchronization.