Definition
A system on multi-engine airplanes that automatically matches the rotational speed (RPM) of all propellers to a single reference, eliminating the slight RPM differences between engines that cause a pulsing beat sound and vibration in the cabin.
Plain English
A device that keeps all the propellers spinning at exactly the same speed so the engines sound and feel smooth instead of producing that wobbling, throbbing noise you sometimes hear in twin-engine airplanes.
Context Anchor
Encountered in multiengine airplane operation, especially after power and propeller controls are set for cruise flight.
Derivation
From Latin synchronus, meaning 'happening at the same time' (syn- 'together' + chronos 'time'). The system makes the propellers turn together in time.
Why Pilots Care
Unmatched propeller speeds produce continuous vibration and noise that increases fatigue for both pilots and passengers on long flights.
Analogy
Like tuning two ceiling fans to the exact same speed so their blades do not create an annoying wobbling hum.
Intuition Check
Propeller synchronization does not mean both engines are producing exactly the same power. It means the propeller speeds are being matched.
Example Sentence 1
After leveling off at cruise altitude, the pilot engaged propeller synchronization and the cabin noise smoothed out immediately.
Example Sentence 2
Many light twins include an automatic sync mode that keeps both propellers turning at the same RPM.