"Dennis O'Connor" wrote in message ...
Either the prop governor, or the piston in the hub are going to hell in a
handbasket... The engine 'stalls' when the prop goes into feather - I doubt
that there is an engine problem... Sending the governor out for overhual
immediately, would be my inclination...

snip

First off, there is a mechanical high-pitch propeller stop that should
be engaged somewhere 1500 rpm and disengaged 1500 rpm. This stop
enables feathering in-flight, but should prevent it at engine
shut-down. This mechanism has rather obviously failed. How come
across it in the past several times, typically the prop feathers AFTER
the engine is shut down.

Also, if everything is working properly, the oil pressure delivered
from the prop governor to the propeller should keep the propeller
against the fixed low-pitch stop during un-"governed" operation. As
in, unless the governor is sensing the engine rpm is too high (prop
pitch too low) and starts to dump governed oil pressure, the propeller
should stay in the low pitch setting.

If the engine is not supplying sufficient oil volume to the governor,
governor will not supply sufficient pressure to the propeller.

With the propeller feathering at low/no rpm, it must be
inspected/repaired. Then the first step in diagnosing a strange
"governor" problem is ensuring that the proper amount of engine oil is
present at the governor pad. The tooling to accomplish this also makes
it easy to check the prop oil supply path from the other passage at
the governor pad through the front main bearing to the prop galley in
the crankshaft.

TC