Re: What is "synchronizing" propellers and why was it done?

Date:         26 Dec 97 03:28:55 
From:         Sjoerd Postma <Postma@nlr.nl>
Organization: NLR-VV
References:   1 2
Next article
View raw article
  or MIME structure

Bob Mann wrote:
> Multi-engine equipment used electrical or mechanical propeller synchronizers,
> phasers and in some cases, combined synchro-phasers, to reduce the frequency
> and magnitude of vibrations associated with "beating" of propellers that were
> out of speed and phase (angular/rotational) synchronization.  Reduced
> vibration contributed to lower cabin noise and lower vibration/cycle fatigue.
> Phasing was the later innovation, and common on larger-bladed equipment like
> P-3/Electra.

The more recent delivered Fokker50 turboprop did not only have speed and
phase (angular/rotational) synchronization, but also blade matching. It
appeared that the vibration level in the cabin could be optimized by
pairing LH/RH propeller blades. After takeoff, when selecting climb
power, electronics first measure the vibration level of all six blade
combinations by slewing the RH propeller RPM. Then the blade combination
with the lowest vibration level is automatically selected and
maintained.
Unfortunately this comfortable aircraft is not produced now anymore.