Dan,
You are almost right.
Feathering prop and counterweighted prop may do as you say.
The more simple Hartzell prop controlled by oil pressure will go to flat
pitch without oil pressure as when the engine stops running. So, the
real problem is when the engine stops producing power but has oil and does
not seize. The wind milling prop may provide sufficient pressure to allow
you to pull it back to coarse pitch and still keep it rotating enough to stay in
the coarse pitch condition. Otherwise, try to get it to stop.
Hartzell CS prop (non feathering, no counterweights): Prop control forward
= high rpm = flat pitch = lo oil pressure. Prop control back = low rpm =
coarse pitch = high oil pressure.
Grayhawk
In a message dated 6/19/2011 6:56:36 P.M. Central Daylight Time,
dballin@gmail.com writes:
One
point about terminology. There is a difference between
full
feathering props and counterweighted props. When oil pressure
drops,
both go to low RPM (coarse pitch), but full feathering will
obviously
go into full feather position and counterweighted goes
close. Full
feathering need an accumulator (read extra weight
complexity) to get
out of feather were counterweighted will generally
windmill. The
interesting thing ( and I only have what I have been
told) is that the
difference in drag/glide performance is not that
significant.
I wanted a counterweighted prop so when the engine quit it
would go to
best glide configuration without my input. I ended up
with an MT
because of weight and at the time Hartzel didn't have a spinner
that
would fit the Legacy. I think the down side is the issue raised
that
if the engine is still running and the oil pressure is low, the
prop
will go to coarse pitch - not the best, say on take off. The
other
issue is that I think with training, one can get the prop lever
back
to low RPM fairly quickly. Counterweights do increase weight and
cost
so is it worth it? Not sure.
Like everything else, this
is a compromise and you just need to know
the correct procedures for your
install.
Dan
N386DM
hopefully flying this summer
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