Describe how twin-engine propellers are synchronized.

Describe how twin-engine propellers are synchronized.

• A. The master governor RPM is set; a signal from the master governor is sent to a control box that drives a stepping motor to adjust the slave governor and fuel control to match RPM.
• B. A mechanical link ties the two propeller drives for synchronized RPM.
• C. The slave governor is adjusted manually by the pilot.
• D. Synchronization is accomplished by aligning blade angles only.

Answer: (A)

Twin-engine propeller synchronization uses a master-slave control arrangement to keep both propellers turning at the same RPM. The master governor is set to the desired RPM, and a signal from that governor is sent to a synchronization control box. That box then drives a stepping motor on the slave engine’s fuel-control mechanism, making small, precise adjustments to the slave governor so its RPM matches the master. This automatic correction continues until both engines run in step, reducing vibration from RPM differences. Blade-angle alignment (synchrophasing) is a separate technique aimed at reducing noise and vibration by phasing the blades, not by locking RPM to the master. A mechanical link between propellers isn’t used in modern systems because it can complicate load sharing and reliability, and manual adjustment by the pilot is not how automatic synchronization is achieved.

Twin-engine propeller synchronization uses a master-slave control arrangement to keep both propellers turning at the same RPM. The master governor is set to the desired RPM, and a signal from that governor is sent to a synchronization control box. That box then drives a stepping motor on the slave engine’s fuel-control mechanism, making small, precise adjustments to the slave governor so its RPM matches the master. This automatic correction continues until both engines run in step, reducing vibration from RPM differences.

Blade-angle alignment (synchrophasing) is a separate technique aimed at reducing noise and vibration by phasing the blades, not by locking RPM to the master. A mechanical link between propellers isn’t used in modern systems because it can complicate load sharing and reliability, and manual adjustment by the pilot is not how automatic synchronization is achieved.