Constant Speed Prop Control Intermittent

Stats:
Aircraft Type: RV-4
Engine Type: Lycoming IO-320 B1A (160 hp)
Propeller Manufacturer: MT (Hub Model: MTV-12-C 3-Blade)
Prop Governor: Woodward (Model: M210689)

Problem: Had an issue with the prop control about a month ago. Prop would not cycle during the 1800 rpm run-up (tried about 20 times). Came back to hangar and worked governor manually several times and made sure no loose bracket or control assembly. Everything looked good. Ran the engine at 1800 rpm and prop cycled good during a dozen cycles.

Flew the aircraft 5 times. At each run-up cycled the prop (about 2 times) before takeoff. After flights did confidence check run-ups and again cycled prop (about 2 times). I also worked the prop during the flight multiple times (approximately 10 times). Everything worked fine.

Flew twice a week ago. First flight had no issues.

Second flight:
1. Run-up at 1800 rpm was good with two cycles of prop.
2. Takeoff roll was good with about 2720 RPM and approximately 23? manifold.
3. Shortly after airborne prop raced up to 2850 rpm (noticeable sound and feel) and prop control was not effective.
4. Pulled closed with about 18? manifold to keep prop below 2700 rpm.
5. On downwind, cycled prop control several times unsuccessfully for about half the downwind.
6. On second half of downwind just before base, prop started to work normal, and I cycled it several times with normal results.
6. After landing did another run-up at 1800 rpm and prop cycled normal about a dozen times.

Removed governor (Woodward) and sent to Ameritech. Tested good.

I am out of ideas. Anyone with similar problem and what was the fix. Thanks.

governor vs. prop

I am not familiar with the MTV props, but I suspect they have seals that can fail, and then let the prop go to min pitch (hence an overspeed condition). So wondering if you have any sense on the prop hub condition? If you have a good governor and oil getting to it, really only left with the propeller as the culprit. Perhaps some folks with MTV propeller experience can/should chime in, I only have Hartzell/McCauley and may be off track here for an MTV prop.

Good luck in solving it, will be interesting to hear what the solution is.

Cheers, Mike

Call Peter Marshall at MT Propeller USA in Deland FL. 386-736-7762. This is potentially very serious. I would not fly the aircraft until you talk to them!

Northwest Propeller.

These guys have been taking care of my MT for several years now with very good results and there a lot closer then MT in Florida, The Florida guys are good also just not as handy. http://www.nwpropeller.com/

Ameritech - Redding, CA

These guys are just down the road from you, and do very good work.
http://www.ameritech-aviation.com

Prop Control Problem

Long story but have had prop control problems. RV-8, Superior IO 360, MT Governor and MT 3 blade prop. Intermittently could not get a good check on ground but would function in flight. Finally on last flight, prop was stuck in fine pitch and would not respond. This is a new prop and overhauled Governor. I just performed a LYC Service Instruction 1462A check. Some questions. At idle the direct oil pressure gauge attached at the Governor oil pressure input port read same as idle Oil pressure in airplane. About 68 on airplane, 71PSI indirect gauge. But when power was increased to 1800-2000 PSI oil pressure in airplane read 80 PSI but oil pressure on direct gauge at governor port went up to 120 PSI. After oil warmed up to operating temp (168?) the direct gauge at 2000RPM read 103 PSI while airplane read 79-80 PSI. Question: Does the governor receive unregulated oil pressure directly from the oil pump before the oil pressure is regulated at the output of the oil pressures regulator???
Second question: The differential pressure in the prop circuit read "0" and the instructions say should read 5-35PSI when differential set at 40 PSI. What are the reason you can think of to cause no pressure in the prop circuit? I can think of three: Cracked Crank, leaking main bearing (no metal in last oil filter and oil sample was normal) or leaking rear main crank seal. Any other reasons anyone knows of? No external oil leaks noted in a brand new MT Prop. Less then 20 hours on it.

Gents,

Too far away for you, but advice is advice.

I use a great prop shop in Portsmouth UK called Proptech, here is what Ali Mant, my contact said.


In my humble opinion and not knowing the propellers history and how or where
the aircraft is stored etc.

I would look at the prop and particularly the blade torques / blade
rotation, it might be the blades sticking up and unable to rotate correctly.
Or it could be sludge in the piston area.

My advice, send the prop to a shop for investigation asap, as there might be
something more serious happening, especially after the governor was tested
and found ok.

Hope that helps.

Best Regards.

Ali

Mystery Solved

Removed the prop and found the crankshaft rear plug partially turned sideways and loose in the crankshaft. Apparently what was happening was the plug would get seated enough with oil pressure applied to usually close enough of the leak that the existing oil pressure in the propeller circuit was enough to control the prop even if some pressure was still leaking out the back into the sump. At times when it would not respond on the ground, by the time I brought the RPM up to full RPM the increase in oil pressure at the higher RPMs would seat it enough to function. Eventually on the last flight, it wedged open enough to allow insufficient oil pressure to control the prop. Now have to get the experts to pull the old plug out and insert a new one and seat it in place. Requires some special tools based on what I have read. If anyone knows of a you-tube video or any video of the procedure let me know. But I now know the origin of my problem and it should not require a tear down.