On Apr 6, 12:50 am, TheSmokingGnu
wrote:
How exactly does a synchrophaser work?

An engine or engines are slaved to a master engine, in order to reduce
noise, usually by getting their propeller / turbofan beats to cancel
each other.

What is it measuring to make its adjustments?

Depends on type, but figure a set of position sensors. Super advanced
models also use noise sensors to dynamically adjust phase offsets in
flight.

Why does it have to be off for takeoff and landing?

Depends on model. Some don't. Older ones work by reducing engine
speed rather than boosting it, thus you could get into a downward
spiral, which is dangerous at T/O.

Kev