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Upshift / Downshift


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Hey HerkyWorld

Got an unusual situation here. Engine starts normal, LSGI torque set correctly. When

the LSGI button is pulled to upshift to Normal Ground Idle, torque stabilizes for a

moment at +-1200"lb ........ then increases to +-6000"lb, rpm decays to 94%, and

TIT increases. Also prop noise indicates the engine is labouring. When LSGI button

is pushed in, everything returns to normal. Standing on the blade line, you can see

the pitch change occurring.

Changed out valve housing, pitchlock regulator, and low pitch stop. Also removed all

cannon plugs to remove electronic influence - no good! Stays the same .....

Anyone out there seen this before? any ideas, theories ........ anything?

Have a great day


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To clarify the problem, let's see if I can restate this more in the terms that I think of this system: At approximately 72%, everything seems fine - even if left at 72% for a couple moments? However, when brought to approx 97%, torque moves from the normal level of 1200 pounds or so momentarily and the climbs up to a value that overloads the engine and RPM decreases to 94%. The only apparently influence that causes this is RPM?

Somehow, hydraulic pressure is getting out to the dome and pushing the blades to increase pitch - but only at normal ground idle RPM. The normal increase-pitch pathway of fluid has been replaced (valve housing). The normal source of this pressure fluid has not (pressurized sump and pump housing pumps).

Is it possible that there is a crack (or check valve) in the pump housing that allowed pressurized fluid to make its way into the side of the dome that increases pitch - as in a backflow of some sort?

I think I'd be removing the pump housing and applying a strong light and magnifying glass to this pump housing. Somewhere, the return fluid from the dome may be backing up the return fluid from the dome and actually pushing fluid to the dome. I say that only because the other sealed areas that separate pressure fluid chambers has already been replaced.

I definitly would like to know what you find. I may never see it or hear of it again, but I might remember this one for a long time.

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Ignore this thread, it somehow got duplicated. The real thread is here http://herkybirds.com/forums/showthread.php?t=1985

For info, the problem is definitely NOT on the engine. We ran it with another prop without

any hassles. The problem prop received a valve housing removed from a tear-down, and

quite happily made the seal break-in run for another engine this morning

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