Kevin Horton
Well Known Member
I should get my RV-8 flying again in August, but I'll need to troubleshoot an issue with my prop governor/engine/prop. It works great initially, but as the oil warms up the max rpm slowly decreases. I'll have 2700 rpm for take-off, but as the flight progresses the max rpm will slowly decrease to around 2580 or so. The engine oil pressure is running in the low 80s. The prop is a counterweighted MT prop, which defaults to coarse pitch and needs oil from the prop governor to push it towards fine pitch. The prop governor is a PCU-5000, set up for a counterweighted prop..
The prop governor manufacturer wants me to do a check for internal oil leakage. They said:
>> The other
>> problem could be engine internal leakage, the oil transfer collar or
>> the crankshaft plug could be causing a loss in pressure as the
>> engine reaches operating temperature. The flyweight system is set up
>> to prevent the engine from exceeding the 2700 rpm, but the governor
>> can only maintain this rpm with good oil supply. The propeller
>> counterweights/internal spring are overcoming the governor pressure
>> and causing the rpm drop. The governor is fighting to overcome these
>> forces. Check with your engine shop on performing a differential
>> pressure check on your propeller oil transfer collar
>> to check for internal leakage and check crankshaft plug for damage.
Lycoming SI 1462A seems to apply:
It describes a complicated test setup which requires me to remove the prop governor and install a blanking plate. You then use a differential compression tester to measure the leakage in the prop control circuit.
I'm still trying to puzzle out why I need to remove the aft-mounted prop governor. If I understand correctly, the place they tell me to hook up the air is over the port that the governor uses to send oil from the governor back to the engine case, where it is then routed to come out a fitting next to the prop governor, and then into the oil line that goes to the front of the engine. I think I could run the same test by just hooking the differential pressure stuff to the fitting at the front of the engine where the prop oil line goes. I think that if I do the test this way, the only think it would miss would be an internal leak between the hole on the governor pad where the oil returns to the engine, and the fitting on the side of the governor mounting pad where the oil line to the front of the engine hooks up.
If I leave the prop governor in place, and it fails the test, that tells me I have a problem up at the front of the engine. Either a leaking crankshaft plug, or excessive clearance in the transfer collar. If it passes the test, that tells me I need to pull the prop governor - either it is bad, or there is a problem at the gasket, or maybe a leak between the prop governor base and the fitting where the prop oil line connects. I could check for that leak after I pull the governor off.
I had a terrible time getting that prop governor installed even when the engine was hanging from the engine hoist. There is very little clearance between the nuts and the governor body. I do not look forward to removing and installing it with the engine on the aircraft.
Comments?
The prop governor manufacturer wants me to do a check for internal oil leakage. They said:
>> The other
>> problem could be engine internal leakage, the oil transfer collar or
>> the crankshaft plug could be causing a loss in pressure as the
>> engine reaches operating temperature. The flyweight system is set up
>> to prevent the engine from exceeding the 2700 rpm, but the governor
>> can only maintain this rpm with good oil supply. The propeller
>> counterweights/internal spring are overcoming the governor pressure
>> and causing the rpm drop. The governor is fighting to overcome these
>> forces. Check with your engine shop on performing a differential
>> pressure check on your propeller oil transfer collar
>> to check for internal leakage and check crankshaft plug for damage.
Lycoming SI 1462A seems to apply:
It describes a complicated test setup which requires me to remove the prop governor and install a blanking plate. You then use a differential compression tester to measure the leakage in the prop control circuit.
I'm still trying to puzzle out why I need to remove the aft-mounted prop governor. If I understand correctly, the place they tell me to hook up the air is over the port that the governor uses to send oil from the governor back to the engine case, where it is then routed to come out a fitting next to the prop governor, and then into the oil line that goes to the front of the engine. I think I could run the same test by just hooking the differential pressure stuff to the fitting at the front of the engine where the prop oil line goes. I think that if I do the test this way, the only think it would miss would be an internal leak between the hole on the governor pad where the oil returns to the engine, and the fitting on the side of the governor mounting pad where the oil line to the front of the engine hooks up.
If I leave the prop governor in place, and it fails the test, that tells me I have a problem up at the front of the engine. Either a leaking crankshaft plug, or excessive clearance in the transfer collar. If it passes the test, that tells me I need to pull the prop governor - either it is bad, or there is a problem at the gasket, or maybe a leak between the prop governor base and the fitting where the prop oil line connects. I could check for that leak after I pull the governor off.
I had a terrible time getting that prop governor installed even when the engine was hanging from the engine hoist. There is very little clearance between the nuts and the governor body. I do not look forward to removing and installing it with the engine on the aircraft.
Comments?