Synchronising props on the Hastings was a dark art of the FE's revealed to none. Synchronising between 1&2, and 3&4, was simple enough. The Capt would tweak the #1 RPM so that the shadow cast (if at night seen by shining the Aldis Light out of the window) across the blades of 1&2, which would be slowly moving, became stationary. Similarly the FE looking out of his window on the RHS of the a/c (or the CP) would synch the #4 to #3. This would leave an audible beat between the inners (3&4). This could then be taken out by then tweaking the #3 (usually). The shadow cast between 3&4 would then start moving again, so once more the #4 would be adjusted. The synch would then be complete, until someone (usually the AQM!) complained again about the beat in the cabin. Repeat as above on all 4!

This is only my theory as it was never spelled out (especially to inquisitive young CP's!), so unless anyone is prepared to reveal all (and then be blackballed out of the FE club), that is the best I can offer.

My father described this system of synchronisation as 'ghosting'.