C/S prop not constant

[jrbrown_143]

Hello All,
Hoping someone can help with a prop question.
RV7A with a XIO-360-A1A has a Hoffman C/S composite prop with a PCU5000X governor.
On runup the prop cycles appropriately,
However in level flight can only get prop to decrease to 2500 despite any further pulling of the prop cable.
As I ascend, the prop speed then decreases to 2300, and when I head down, it speeds up back to 2600 even with small attitude changes.
Cant seem to keep it constant with small changes in attitude.
Sent in Governor and its bench tested fine. stops are in place where should be.
Prop was recently overhauled and has less than 50 hrs.
engine running fine otherwise. no leak or oil on prop.

The front of the Hoffman has some sort of pressure relief valve that I'm not familiar with however, wondering if this needs an adjustment?
Also when the plane is sitting, I can very easily move the blades through their fine-coarse pitch range by twisting them.

Sent messages to Hoffman, however they keep sending to more and more technicians trying to figure it out.

anyone familiar with Hoffman props could offer some insight??

Jon

[miyu1975]

Anything changed on the engine lately.?..ie recent overhaul.

Also, being able to twist the blades on the ground is normal but usually not very ?easily?. At least for me it takes a pretty solid effort to twist them by hand.

[Jpm757]

Not familliar with the Hoffman prop, but does the prop dome require a nitrogen charge?

[9GT]

You might want to start with the Lycoming propeller leak test: https://www.lycoming.com/sites/defau...0Procedure.pdf

[jrbrown_143]

thanks for the replies.

The engine is newly overhauled and 40 hrs on it now. Talked to the shop that overhauled it, the recommended I had the prop overhauled even though it has 40 hrs on it as well.

Not sure on the nitrogen charge, I havent seen anywhere in the prop manual and documents form Hoffmann about that, however sent an email to Hoffmann asking.

Going to do the Lycoming leak test
and flush all the oil lines in case of sludge or mechanical blockage

Hope to get it figured out!

[dlloyd3]

Sounds as though the coarse pitch stop in the propeller is set improperly for the RV's speed range. To check, go to cruise speed and set 2600 RPM. In climb, does it remain at 2600? If so, the prop governor is working properly. In descent, RPM should remain at 2600. Again, everything is working properly and the symptom you describe would point to the coarse pitch stop. With a Hartzell this can only be adjusted with the prop disassembled, don't know about Hoffman.

[Bill Boyd]

I have a low-time Hartzell C/S prop sourced by Van's and removed from another -10, with 150 hours or so on it. Bolted to my newly O/H'd engine that has not run yet. No way could I twist those blades by hand without some kind of tool for leverage. I've tried, so I could size the cutouts in the spinner - and will have to find a way to do so eventually - but I assumed this was normal.

Should I be able to muscle the blades of my prop to a different pitch without needing a blade wrench of some sort? If so, I need a gym membership.

[lr172]

Originally Posted by Bill Boyd

I have a low-time Hartzell C/S prop sourced by Van's and removed from another -10, with 150 hours or so on it. Bolted to my newly O/H'd engine that has not run yet. No way could I twist those blades by hand without some kind of tool for leverage. I've tried, so I could size the cutouts in the spinner - and will have to find a way to do so eventually - but I assumed this was normal.

Should I be able to muscle the blades of my prop to a different pitch without needing a blade wrench of some sort? If so, I need a gym membership.

No way on my new prop. Used may b a tad looser, but doubtful yuo could do it without leverage. I just used a paddeed clamp and a 2X4. Worked fine.

[dlloyd3]

No way to simply grip the blades with your hands and give it a twist. Nope. Make a couple blade paddles, pad to avoid scratching your new paint. It will be pretty stiff, best done with a helper. A used prop may be easier.

[BillL]

Originally Posted by dlloyd3

Sounds as though the coarse pitch stop in the propeller is set improperly for the RV's speed range.

This happened to me and wasted a lot of time with the leak test, and governor work.