Oil leak MT Prop

[Antoine]

Russ mine did not leak as much as yours. What I got on the fuselage and canopy were tiny droplets of the same color as yours, but you really have more. I would have it fixed. My suggestion remains to send the info/video links to MT USA and ask for assistance.

[Rich]

Russ mine did not leak as much as yours. What I got on the fuselage and canopy were tiny droplets of the same color as yours, but you really have more. I would have it fixed. My suggestion remains to send the info/video links to MT USA and ask for assistance.

Yeah, I second that, Russ. Yours looks to me like it could be more than just simple grease-seal leak. I have 1 blade throwing a bit of grease right now, between the seal and the blade ferrule. In your case you appear to have it coming out beneath all 3 seals.

[Chris B]

I realize that this discussion is about an MT prop. But FWIW, a Hartzell tech at OSH indicated that their seals have a limited *calendar* life (replace about every 7 yrs, 10 years max). Something similar may apply to MT props.

Chris

[carym]

I realize that this discussion is about an MT prop. But FWIW, a Hartzell tech at OSH indicated that their seals have a limited *calendar* life (replace about every 7 yrs, 10 years max). Something similar may apply to MT props.

Chris

The MT prop (at least on my DA42) has a 72 month TBO. I just went through the overhaul at a cost of just north of $10,000 and nothing over a standard overhaul needed to be done.

[dmloftus]

Flying home from Greenville yesterday, I noticed a very small streak of oil or grease on the back of my MT composite prop blade. Is this an immediate concern or something to just watch before I bring my plane in for annual in a couple of months? It’s probably just a single drop that spread up the back of blade #1. While I normally check for prop play and nicks in my preflight, I can’t say exactly when this small streak appeared. I pulled the spinner and took pictures of all 3 blades. Blades 2 and 3 seem to have very small grease marks on the hub but nothing coming up the blade. The small trickle on blade #1 feels slightly sticky, not runny like I would expect if it were oil, and you might notice where I rubbed it a bit and it smeared. There is nothing on my windscreen, on the inside of the spinner, or on the cowling. And my oil consumption is about normal. The prop was rebuilt about 300 hours ago.

One pilot website recommends wiping the blade clean with a cloth with mineral spirits, starting the engine, and running the prop lever back and forth at least 5 times to see if any additional oil/grease appears. Several articles mention the possibility of an excessively greased hub emitting small amounts of grease. They say if nothing more appears, there is likely no immediate problem. But if new oil appears, that the prop is likely in need of overhaul. Does this make sense? Also can mineral spirits be used to clean the small amount on the composite prop (they may have been referring to a metal prop)?

[Rich]

David, the prop hub contains grease and usually this is what oozes out a bit from time to time. I would wipe it down and watch it. How long ago was the overhaul, not in hours but years? The single streak could indicate some deterioration of that seal.

[dmloftus]

Hi Rich,
Prop OH was 4 years ago. I'm flying to TX this week and will monitor it closely. But I'm also planning to go to Vegas, with a few passes over the Grand Canyon on the way, before my annual. Hate to have a catastrophic failure over the canyon. My thought is the chance of completely blowing a seal is very remote. I'm thinking I would have some advanced warning with increased leakage if it is really a seal leaking, right? Thanks!

[Rich]

After wiping it down, try to get a few hours in. Cycle the prop a bunch and vary your airspeed and RPM a few extra times (to get the pitch to vary under load) and monitor the blade roots. The little bit of oozing you see elsewhere is definitely not worth worrying about.

In the past many of us have experienced the little black grease dots on the cowl and windscreen. This was more common with earlier grease types (and other parts) MT used. I did have a serious failure in 2009 not related to leaks, per se, but crappy grease MT used back then. It was not a sudden catastrophic failure, but it did wreck the ball bearings and blade ferrules such that the prop acted almost like a fixed pitch prop. But it soldiered on for thousands of miles before it was pulled and sent for overhaul. I misdiagnosed the problem as being a governor
problem, which is why I let it go on so long.

The oil leak that turned up in this topic is the first I've ever heard of.

[dmloftus]

Yes I agree with it likely being grease as it is only on the one blade. Seems if it were oil from the governor I would be seeing it more places. Thanks for the advice on exercising it - will definitely do so.

[Rich]

Also, not to be alarmist, but when wiping that streak off, I'd take a careful look and make sure that there isn't a crack in the metal underneath that grease.