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Fine Oil mist on 1/2 of Windscreen (RV-6A)

B

bill.hutchison

Well Known Member
I'll be digging into this tomorrow morning, but figured some of the collective wisdom here could help point me in the right direction...

First - I did read this thread about atomised oil on the windscreen and then this other thread which was similar in nature.

Last two flights I've done I noticed a very fine mist of oil on the right-side of my windscreen. Also noticed a bit of oil spatter on the right side of the intake. I've always had a bit of smoking rivets in the photos as I've cleaned up various leaks, but I'm starting to wonder if there is a correlation here?

In any case, the following facts are relevant:

  • The airplane just came out of condition inspection, and the mechanic did replace the gasket for my prop governor. My engine is an ECI Titan O-360 with the governor mounted on the rear of the case, and a Hartzell CS prop.
  • The prop has not been overhauled in a while, has not been leaking or weeping oil that I can tell. I'll pull the spinner tomorrow to verify.

I have an A-hub on the prop and it's coming up for the eddy current inspection (I had planned to pull it this week) and I've been considering just replacing the prop entirely. An overhaul and new hub would put me pretty close, costwise, to what I could buy a new Hartzell Blended Airfoil prop for from Van's.

Although I do wonder about used Hartzell BA options. Thoughts on that?

Thoughts on this mist?

I'll post more when I know more, but if you guys have some ideas off the top I am all ears.

Thanks!
 

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My uninformed guess is the prop was greased and when it got hot again it spit some grease - this happens on mine even when clearing the plug hole, I dont remove the zerk since the plugs have been installed.
 
Your pictures look similar to what happened to my RV after a condition inspection. The prop was greased during the inspection and unfortunately a small grain of dirt got lodged in the grease fitting keeping it from sealing completely. Recommend you remove spinner, check for signs of grease above the location of the fitting. If found, remove fitting, clean it, check for complete fitting then reinstall.
 
It doesn't look like prop grease.

The spatter being on the right side only or at least primarily is telling us something about where the leak is coming from.
 
Maybe this >

If greased with Aeroshell #6 the oil in the grease does separate and will make it out through the seals and cause it to leak and mist the windshield, or the seals may need replacing = prop overhaul.
 
Spitting grease

I would see a very slight spitting of grease initially but after sitting waiting for paint did the exact same thing same location. (4.5 months) Spinner removal will confirm the issue. Removed the prop and had it repacked with a grease that is not supposed to separate. 100 hrs. later, perfect.
 
If it's oil, pull the cowl. Look for a oil spatter on the lower front cowl, the pattern will give you a hint where it's coming from.
Also feel the inside of the flywheel pulley. If it's wet there, you have a front crank seal starting to fail.
 
jeffw@sc47 said:
If greased with Aeroshell #6 the oil in the grease does separate and will make it out through the seals and cause it to leak and mist the windshield, or the seals may need replacing = prop overhaul.
Click to expand...

I changed my Hartzell blended airfoil prop grease to Aeroshell #5 and it solved a similar problem I was having.
 
That looks like engine oil, not grease, on your cowl picture. If it is prop grease, and it flung that much that quickly, you will know right away when you remove the spinner as others have said.

This has been brought up before; don't over grease the prop. One reason I do my own CI's. Some mechanics see a grease fitting and start pumping away....
 
Pulled cowl and spinner. Initial impressions:

  • Exterior front lip of cowl (face of the cowl facing the back of the bulkhead) has slight residue on it, light caramel color like engine oil.
  • Back of the pulley is dry - can’t see any oil spatter or feel any either.
  • Inside of cowl doesn’t have any new grease or oil stains.
  • Prop hub - one of the flat “faces” of the hub has a sticky oil residue - same color as the spatter on the outside of the cowl and the windscreen. No other hub surfaces are wet or sticky, just the one side.
  • There is similar oil residue on the bulkhead surface where the spinner screws attach, oriented in the same place as the sticky spot on the hub.

My mechanic is going to meet with me tomorrow and give me his thoughts. It’s also worth noting that the Zirk fittings have all of their covers on them.

If it turns out that I need a prop overhaul, this is going to be problematic. As I understand it, the A-hubs cannot be overhauled. The cost of a B-hub plus overhaul cost comes to around $8500-$9000. That about right?
 

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Just another opinion
Prop seal maybe ?
But then
I've seen it/done it where maybe I've lubricated something a little too much and the residue has found its way out of the cowl
Air behind the prop/spinner moves in a lot of directions
I've even seen air move forward and out of a cowl and put oil on the windscreen
Mike
 
Further impressions...

It appears there is a glob of grease inside the spinner (picture attached) that I didn't notice at first when I pulled it.

I went to the local mech's shop on the field and asked him if I could get a tiny sample of aeroshell 5 and 6...it's the same light caramel color as what's on the airplane, and it's stickier than engine oil, too.

This makes me think that it's prop grease, and evidence seems to be mounting that it was over-serviced by a tech. The glob of grease in the spinner is in a position that aligns with the sticky face on the prop hub.

I'm ALSO thinking (and tell me if I'm wrong here) that this is more likely over-servicing because if there were blown seals in the hub, it would be flinging some grease onto the blades, and the blades appear to be completely dry.
 

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mvs163 said:
Just another opinion
Prop seal maybe ?
But then
I've seen it/done it where maybe I've lubricated something a little too much and the residue has found its way out of the cowl
Air behind the prop/spinner moves in a lot of directions
I've even seen air move forward and out of a cowl and put oil on the windscreen
Mike
Click to expand...

I checked the back of the pulley - it's dry all the way around. The only evidence of anything wrong is sticky oil/grease on the hub.
 
Hartzell has very specific instructions for the quantity and this indicates maybe someone doing more...........
 
gnuse said:
Hartzell has very specific instructions for the quantity and this indicates maybe someone doing more...........
Click to expand...

...and this still may be too much. There are some good discussions on this in the forums. Now to find them ;)...
 
..also, to add......

When I had my prop overhauled, they replaced the O rings. The prior rings where a squared off shape, not the standard O shape. Evidently, once the "old" style rings passed grease, they would continue to do so, regardless. The new O rings where supposed to be better sealing. Also, as mentioned, switching to Aeroshell 5 if you haven't already, and I haven't had any issues and am just about ready for a another rebuild, or inspection and reseal.

My prop is a "B" hub manufactured in 2005. Perhaps someone with more knowledge can elaborate,,,,
 
JonJay said:
..also, to add......

When I had my prop overhauled, they replaced the O rings. The prior rings where a squared off shape, not the standard O shape. Evidently, once the "old" style rings passed grease, they would continue to do so, regardless. The new O rings where supposed to be better sealing. Also, as mentioned, switching to Aeroshell 5 if you haven't already, and I haven't had any issues and am just about ready for a another rebuild, or inspection and reseal.

My prop is a "B" hub manufactured in 2005. Perhaps someone with more knowledge can elaborate,,,,
Click to expand...

Checking back over the prop logbooks, it has been consistently serviced with Aeroshell 5. So that's good, I guess.

I just had a conversation with East Coast Props and it turns out I CAN have it overhauled as long as I'm keeping up with the 100-hour AD.
 
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Bill was there any grease inside the spinner?

Although it sure seems like prop grease, I assumed it would come from the zerk - they do have some that will pop open at a certain pressure. But - -the fact that all dust covers were on the zerks, and I assume no grease underneath is curious.

Just to settle it - I might just remove the zerks and clean the holes with toothpick and q-tip cotton swabs. Then reassemble and fly, if some other smoking gun is not found. I did this on mine and it did not come back until I put more grease in at the next annual (CI).

BTW - 250hrs on the prop. And I have gotten mist on only one side before.
 
BillL said:
Bill was there any grease inside the spinner?

Although it sure seems like prop grease, I assumed it would come from the zerk - they do have some that will pop open at a certain pressure. But - -the fact that all dust covers were on the zerks, and I assume no grease underneath is curious.

Just to settle it - I might just remove the zerks and clean the holes with toothpick and q-tip cotton swabs. Then reassemble and fly, if some other smoking gun is not found. I did this on mine and it did not come back until I put more grease in at the next annual (CI).

BTW - 250hrs on the prop. And I have gotten mist on only one side before.
Click to expand...

Yeah - look at my post a couple entries up - there was a dollop - maybe a teaspoon worth - of dark grease inside the spinner.

Weird that it was localized in a clump and not flung around in a ring, but I don't know what I don't know here...
 
bill.hutchison said:
Yeah - look at my post a couple entries up - there was a dollop - maybe a teaspoon worth - of dark grease inside the spinner.

Weird that it was localized in a clump and not flung around in a ring, but I don't know what I don't know here...
Click to expand...

Sorry, I missed that - -think rotating gravity - - the drop simply followed the radial. That should give you a major clue as to where it originated. "Typically, all the information we need is right in front of us." Or so I have been told. And - -grease will drop at 1 G but at some point it will flow and may separate the oil from the wax. The little clumps are wax. That is the clue it was grease. It appears a stream flowed under the backing plate by looking at the grease blob closely.

Now, why it it only on one side of the windscreen is still a mystery for me. I was thinking maybe the downwash of the prop vs upwash on the other side. :confused:

I hope it turns out as a benign event.
 
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BillL said:
Sorry, I missed that - -think rotating gravity - - the drop simply followed the radial. That should give you a major clue as to where it originated. "Typically, all the information we need is right in front of us." Or so I have been told. And - -grease will drop at 1 G but at some point it will flow and may separate the oil from the wax. The little clumps are wax. That is the clue it was grease. It appears a stream flowed under the backing plate by looking at the grease blob closely.

Now, why it it only on one side of the windscreen is still a mystery for me. I was thinking maybe the downwash of the prop vs upwash on the other side. :confused:

I hope it turns out as a benign event.
Click to expand...

You and me both, buddy.

Between this and the SB for the spar lately, I'm questioning my sanity when it comes to this thing, especially since I made a career change and fly for a living now.

I do want a new prop - this 100 hour AD is an inconvenience.

But it's a much cheaper inconvenience than a new prop.
 
Check your oil filter. Early in my flying adventures I torqued the filter to exactly the right amount. After an hour flight I noted some oil on the wind screen.
Turns out that it was leaking at base of filter. After that I always tightened the filter more than exactly the correct torque setting.
 
I have been there - that dump of grease in the spinner tells me that the zirk fitting is loose or leaking. I have played in that move before. NO DOUBT about it as centrifugal forces causes the grease to deposit in a nice dump opposite the zirk fittings.
 
I originally had a prop slinging oil from separated aeroshell 6 in a new prop. It continued longer than I expected and ultimately found that what started as separated oil from the prop seamlessly changed to a slight oil leak from the lower case seam near the front of the engine (the clue was I no longer noticed oil streaks on the prop blades). They both left a very similar trail from the right cowl inlet back to the windshield. Apparently oil leaks near the front can get pulled out of the right inlet and then stream back along the cowl top. Once I addressed the seam leak, it all stopped.
 
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So I had a discussion with the mech who worked on the airplane, and while we were talking about it, he pointed something out which had completely escaped my memory....

...while his guys DID service the prop, the mist-on-the-windscreen issue had been happening before the annual. We actually had a short conversation about it when I dropped the airplane off for annual back in December. With airline training and everything I completely forgot about it. But he's right - it was doing that before I brought it in and we did talk about it.

He doesn't think a seal is blown but can't tell for sure.

May be time for overhaul after all.
 
I had the same Grease Problem - Now Solved

My new Hartzel Prop had the same problem after about 60 hours. It spit grease on the Right side of the windshield. I put new after market silicone seals in the prop and it solved the problem. The inside of my spinner had grease in it also. I can see clearly now the grease is gone!
 
dwalters said:
My new Hartzel Prop had the same problem after about 60 hours. It spit grease on the Right side of the windshield. I put new after market silicone seals in the prop and it solved the problem. The inside of my spinner had grease in it also. I can see clearly now the grease is gone!
Click to expand...

Good to know. You had a shop do this? What did it cost?
 
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