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The Hamilton-Standard props used on B17/B28/B24 etc. used a separate oil
pump to feather the engine which also unfeathered if the switch/button was
held in. The B26 and some other airplanes used electric prop motors and
switches to control the prop. These were the ones that would run away.

The accumulators only function is unfeathering, although they might serve as
surge tanks. CS operation is only by governor boosted engine oil being
directed to or allowed to drain from the prop. Aerodynamic and inertial
forces acting on the prop blades is either countered or assisted by the oil
pressure acting on a piston with linkage or cams to alter the prop blade
angle of attack.


--
Jim Macklin
ATP, CFI-ASMEI, A&P
"Fredrik Thörnell" wrote in message
news:39D07273.4A4FE01E@student.mdh.se...
> RT wrote:
>
> > However, going for min rpm (=max pitch) would prolly make you feel
better
> > even if it didnt happen :-)
>
> If you lose oil pressure, the prop of a single engine A/C is supposed to
go to
> fine pitch by design.
>
> > In a twin an accumulator (hopefully) allows you to feather.
>
> In a twin they work the opposite and automatically feather. In turboprops
all
> the time, in reciprocals only when above a certain RPM since starting up
the
> engine with the props in full feather would put too much load on the cold
> engine.
>
> Certain to be exceptions. Didnt the B17 for one have a problem with props
> going into fine pitch and revving up until the bearings seized and they
fell
> off in early models before they added feathering accumulators? I seem to
> recall reading about that.
>
> Cheers,
> /ft

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