AKar wrote: ↑
18 Jul 2020, 01:00
[...] and even in case of governor failure, the eventual overspeeding will be somewhat gradual as the aircraft picks up speed.
Of course, I must add that in case of twins, the propeller acts the opposite way to the ones in the singles. That is, towards the feather. The scenario above would be modified to add some further failure modes for the twins.
In case the governor fails to ever produce oil pressure to the hub after start-up, the propeller would probably rest on its start locks. This would be evident by the engine not just reaching its usual static RPM, though the error could be quite a subtle. I'd consider this failure mode very remote, except perhaps if the airplane had some recent work done on the governor.
In case the governor fails to provide oil pressure to the hub some time after the start-up but before or during the take-off power application, if
occurring during running at elevated RPM, the failure would result in the propeller feathering, which would be readily obvious (though it could happen rather slowly).
Failures in the governing function itself work almost the same as in the singles.