Hi Discorde,

Very interesting and sophisticated. It sounds as if the syncrophaser should have stopped any de-synchronous beat of the kind I assume was causing the resonance in the fuselage skin. Presumably it was selected off or u/s. How reliable was it?

As Alan notes above, the synchro meter sounds identical to the one on the VC10. But it was also on the DH 114 (Heron)... And I seem to recall that the props on the VC10 were a lot smaller, faster, and further aft. ;)

We're going back more than 40 years Chris. I can't remember whether the synchrophaser was active at all times or only for the cruise. I suspect the latter. Was it reliable? As I recall the mini-props would usually be stationary, indicating RPMs in synch. If the throttle setting was changed the mini-props would spin until the RPMs were resynched. We rarely changed the throttle settings, though: fully forward for take-off, then at 1500(?) feet, reduce to 12,500 LP RPM for climb and cruise, accepting whatever IAS that setting gave. Max cont was 13,500 LP RPM and 'ops necessity' 13,000.

The synchrophaser was supposed to adjust the props such that the blades intermeshed as they rotated, as represented below, which again was supposed to mitigate vibration:

x + + x

I must get out more!