Hi, I joined this forum because googling revealed this is the only place where folks are discussing problems even halfway related to mine.

I look after an RV-8 for its owner and do a CB lot of strip flying and aerobatics in it. It’s a new build, but the builder isn’t contactable. The problem is this: When I cycle the propeller on the ground the engine oil pressure drops to zero briefly as the prop goes fully coarse. I fly another 8 which only drops to perhaps 30psi on the first cycle of the day and improves with each one. On the bad aeroplane multiple cycles only gets me to a minimum of about 15psi. In flight the prop works as it should with no surge and the engine oil pressure is a steady 75psi.

The engine has a full Raven inverted oil system which is correctly configured. The governor and prop are both brand new Hartzell items. I’ve contacted Hartzell who said they had never seen such a problem before and couldn’t help. The inverted oil system maintains good oil pressure in all attitudes.

It seems the engine can make the necessary oil pressure but can’t flow sufficient oil to prevent a pressure drop when the governor opens the floodgates and diverts and pumps the oil to the prop in response to a demand for coarse pitch from the lever.


Does anyone have any suggestions?
Many thanks

Who did you speak with?

What is your prop make/model/SN?

MW

Hi, I didn’t get the name of the guy at Hartzell. The prop is a metal blade blended airfoil HC-C2YR-1BFP/F7497, S/N NS5829B. The governor is a Hartzell S-1-10, S/N G4100NJ. Both of these are 30 hours from new in 2018.

I’m pretty sure something has been assembled incorrectly, I just don’t know what. The problem is the same from when we first had the aeroplane a year ago and hasn’t got any better or worse, so it seems unlikely it’s a component failure thing.

You could check for excessive internal engine oil leakage. Lycoming has a service document that describes the test that is done with the same differential pressure tool used to check engine cyl pressures at annual. I even know of a guy in AK who got a 0TSOH engine done by a well known shop that had similar issue that turned out to be mis-matched bearing parts used in assy that allowed high pressure oil from the governor to escape back to the sump through these bearings.

John

If you have not already, I would first validate the oil pressure gauge. That can be inaccurate at low pressures and causing undue concern.