A couple of choices: Engine isn't producing full
horsepower-- or prop/gov are faulty.

If the prop will run at command RPM with variation
in manifold pressure while in flight, I'd say governor
is OK. If it won't go to redline, but runs correctly
at other rpms, it's a linkage or command problem.

Some props won't go clear to redline until you
roll along awhile. That is a function of the fine
pitch setting on the prop. Props should be alike.

When you are tooling along, it should go to
redline rpm no problem even if engine is pretty
lame. As you change manifold pressure, does
the rpm overshoot and undershoot the target by
small amounts? That would be normal.

If it's low rpm only on takeoff, it could be the
prop is on the fine pitch stop and the engine
just can't spin it to red line there. If it's the
engine, I'm in agreement with the camshaft
crowd. This is a problem on Dukes. On
those, you can detect the problem by comparing
fuel flows... if the ff is low, the engine isn't pumping
enough air which is usually a cam.

I'd think if it was a friction problem it would have
destroyed itself early in the flight. Think of the
kilowatts of power involved!!

Bill Hale BPPP instructor/ A&P


wrote:
Trust me. I'm not flying an airplane with unexplained power loss or a
misbehaving propeller. If you lose the left one, the right one is
sick. If you lose the right one, maybe it won't feather. (I plan on
getting old.)

I'm just trying to figure out if there is something else to look at
before things get really expensive and time consuming. (It wouldn't be
fun to pull the engine and send it out to have it turn out to be fine,
and you just can't swap them around as easily as governors. :-)).

-Rob

Denny wrote:
A bad cam is one likely problem... The other and more ominous is that
you have a binding engine and are set up for catastrophic
failure/seizure on takeoff... A 100 hour engine that won't make RPM is
a hand grenade with the pin pulled... Don't fly it again and send it
back... Insist they put 3 hours on the dyno after it is repaired and
that it make target HP and RPM...

denny - old pilot with the scars, financial and otherwise, to prove
it...