Definition
An electronic system used on multi-engine propeller aircraft that maintains the propellers at the same RPM and holds the blades of each propeller at a fixed angular position relative to the blades of the other propellers. By controlling this relative blade phase, synchrophasing reduces cabin noise and vibration caused by the combined sound waves of the propellers.
Plain English
A system that not only spins all the propellers at the same speed, but also keeps their blades lined up at chosen angles to each other so the noise waves they make partially cancel out, making the cabin quieter.
Context Anchor
Seen in multi-engine propeller aircraft when reducing propeller noise and vibration after the propeller speeds have been matched.
Derivation
From 'synchro-' (Greek 'syn' meaning together, plus 'chronos' meaning time) and 'phasing' (from 'phase,' the position of something in a repeating cycle). So the word literally means 'timing the phases together' — keeping the blade positions in a chosen, steady relationship.
Why Pilots Care
Lower cabin noise improves passenger comfort and reduces pilot fatigue on long flights; it also lessens vibration stress on the airframe.
Analogy
Like adjusting two ceiling fans so their blades sweep past the same spot together instead of creating a pulsing whoosh each time they pass out of step.
Intuition Check
Do not confuse synchrophasing with simply making both propellers turn at the same speed. Synchrophasing also controls where the blades are in their rotation compared with the other propeller.
Example Sentence 1
After leveling off in cruise, the pilot switched on the synchrophaser and the cabin noise smoothed out within a few seconds.
Example Sentence 2
After the propeller overhaul the mechanic verified that synchrophasing held the blades in correct alignment during ground runs.