Hartzel hub burp grease?

[RobertGary1]

I have about 5 years 200 hours on my hub since the last tear down and reseal. After last annual I’m seeing small amount of grease on each blade. All these annuals pumping a couple pumps of grease I wonder if the prop just overfilled and purged some? I’ve never seen grease come out the opposite open zerk. I’ve heard some prop people say a little grease isn’t an issue??? Could it have just been too much eventually?

[DXB]

8 minutes ago, RobertGary1 said:

I have about 5 years 200 hours on my hub since the last tear down and reseal. After last annual I’m seeing small amount of grease on each blade. All these annuals pumping a couple pumps of grease I wonder if the prop just overfilled and purged some? I’ve never seen grease come out the opposite open zerk. I’ve heard some prop people say a little grease isn’t an issue??? Could it have just been too much eventually?

It doesn't sound like you're overfilling the hub if you're putting in just a couple pumps/year and nothing is coming out the opposite fitting.  It is worth knowing what grease was put in the hub at last reseal - generally its Aeroshell 5 (thicker) vs. Aeroshell 6 (thinner).  I bet you have 6, which has a reputation for breaking down and liquifying, generating a thin sheen that gets past the seals (not heavier nodular chunks, which would be more worrying).  With just a small amount of this leaking and the low hours you're flying, I doubt the hub is at risk of running dry of grease , so I would be in no rush to do another reseal job. I've been living with a similar issue for a few years now flying 100-150 hrs/year, adding a few squirts #5 at annual on top of the original #6 in the hub from factory new 11 years ago - it does immediately come out the opposite fitting for me.  There is no problem with mixing the two greases.

[MikeOH]

^^^^ THIS ^^^^

I've had this annoying issue the entire 5 years I've owned the plane.  I sent the prop off for reseal and they accidentally overhauled it!  Still, it leaked so I sent it back....they took it apart put in new (again) seals sent it back...still leaks!  Then I found out about the Aeroshell 6 formulation change that resulted in the separation of the thinner grease components and, thus, the leaking.  Like DXB I just put in Aeroshell 5 at annual and it has become a little better.  Hartzell now approves the use of NYCO GN3058  grease.  If I get sporty with my wallet I'll have yet another prop reseal done with the NYCO and I suspect that will finally cure the problem.

Here's the Hartzell SB which covers this (along with the acceptability of mixing AS#5 an AS#6:

https://hartzellprop.com/SERVICE-DOCUMENTS/SL/HC-SL-61-366.pdf

[Shadrach]

2 hours ago, RobertGary1 said:

I have about 5 years 200 hours on my hub since the last tear down and reseal. After last annual I’m seeing small amount of grease on each blade. All these annuals pumping a couple pumps of grease I wonder if the prop just overfilled and purged some? I’ve never seen grease come out the opposite open zerk. I’ve heard some prop people say a little grease isn’t an issue??? Could it have just been too much eventually?

If it just started, I doubt it’s a grease quality issue and is likely a grease quantity issue. There is no need to grease a prop every annual. It is an illogical service interval. Some planes fly 300hrs a year and some fly 30. Grease does not evaporate so whatever you add, stays in the hub. The bearing races on an aluminum hub Hartzells are only sealed on the external side of the race. Continued servicing will push grease into the hub cylinder. When sufficient grease has accumulated, cycling the prop will cause the piston in the hub to push the grease out the only path available…herniating the seals at the base of the blades..

[RobertGary1]

7 minutes ago, Shadrach said:

If it just started, I doubt it’s a grease quality issue and is likely a grease quantity issue. There is no need to grease a prop every annual. It is an illogical service interval. Some planes fly 300hrs a year and some fly 30. Grease does not evaporate so whatever you add, stays in the hub. The bearing races on an aluminum hub Hartzells are only sealed on the external side of the race. Continued servicing will push grease into the hub cylinder. When sufficient grease has accumulated, cycling the prop will cause the piston in the hub to push the grease out the only path available…herniating the seals at the base of the blades..

Does it just keep leaking then?

[Shadrach]

18 minutes ago, RobertGary1 said:

Does it just keep leaking then?

Usually. That being said, there is no harm in cleaning it up and watching it for a 5-10 hours. 

[DXB]

17 hours ago, Shadrach said:

If it just started, I doubt it’s a grease quality issue and is likely a grease quantity issue. There is no need to grease a prop every annual. It is an illogical service interval. Some planes fly 300hrs a year and some fly 30. Grease does not evaporate so whatever you add, stays in the hub. The bearing races on an aluminum hub Hartzells are only sealed on the external side of the race. Continued servicing will push grease into the hub cylinder. When sufficient grease has accumulated, cycling the prop will cause the piston in the hub to push the grease out the only path available…herniating the seals at the base of the blades..

I think there is some time needed for the the #6 to start breaking down and thin liquid to escape past the seals.  Mine was fine for about 7 years until a bit of thin grease started to appear near the hub on one blade, particularly in summer months.  Hartzell is clear on time and hour interval requirements for greasing the hub, so I would be hesitant to ignore that - I think the idea is to dilute and/or flush old congealed grease. I think they also commonly recommend gently probing around in the opposite fitting to break up any congealed grease might prevent the grease from getting flushed out. A common practice among many A&Ps has been to keep pumping until you have grease coming out the opposite fitting, which Hartzell advises against for the reason you cite - the central hub getting filled and pressurized, causing the seals to herniate.  For my  scimitar prop, they recommend 6 pumps OR to stop the moment grease comes out the opposite fitting.  They might also recommend a reseal job on my prop, which I am resistant to for the time being - the minor appearance of the leak and the fact that grease comes out the opposite fitting after just one or two pumps gives me confidence that the hub isn't about to run dry and self destruct.

[EricJ]

3 minutes ago, DXB said:

For my  scimitar prop, they recommend 6 pumps OR to stop the moment grease comes out the opposite fitting.  

They recommend 1 ounce or when grease comes out whichever is first.    There is tribal wisdom that 1 oz is six pumps, but it is highly dependent on the type of grease gun you have.   It is recommended to check your gun to see how many pumps are required for 1 oz.    Guns that can do high pressure may take many more than 6, and if you have a quality name brand gun the documentation for it might even say how many pumps per oz or particular volume metric.   If you assume 6 pumps, you may be getting much less than an ounce, depending.

 

[A64Pilot]

The common practice of keep pumping until it comes out the other side IS the correct procedure for the larger turbine props, I would always pump until I got fresh grease out, took 15 or 20 pumps sometimes but I wanted to flush out all the old grease. Sometimes you would have to pump several pumps before it started coming out the other side.

However it is NOT correct for our smaller piston props and you can overfill the hub, often the symptom of overfilled is a prop that’s slow to cycle.

Make sure whoever is doing it that you don’t flush these little props.

[1980Mooney]

23 hours ago, RobertGary1 said:

I have about 5 years 200 hours on my hub since the last tear down and reseal. After last annual I’m seeing small amount of grease on each blade. ....

 

2 hours ago, DXB said:

I think there is some time needed for the the #6 to start breaking down and thin liquid to escape past the seals.  Mine was fine for about 7 years until a bit of thin grease started to appear near the hub on one blade, particularly in summer months. ...

 

20 hours ago, Shadrach said:

If it just started, I doubt it’s a grease quality issue and is likely a grease quantity issue. There is no need to grease a prop every annual. It is an illogical service interval. Some planes fly 300hrs a year and some fly 30. Grease does not evaporate so whatever you add, stays in the hub. The bearing races on an aluminum hub Hartzells are only sealed on the external side of the race. Continued servicing will push grease into the hub cylinder. When sufficient grease has accumulated, cycling the prop will cause the piston in the hub to push the grease out the only path available…herniating the seals at the base of the blades..

This unfortunately is a quality issue with AeroShell 6.  As Hartzell has highlighted in letters to shops and owners, for some reason Shell changed the formulation of AeroShell 6 sometime in the mid 2010's.  It breaks down sooner than earlier formulations.  

I have a full feathering Scimitar that was overhauled and refilled with AeroShell 6 at a Hartzell Service Center in 2015.  In 2021 I started seeing streaks on the blades.  Then it got worse and started spattering a film on the windshield.  The warm climate I am in probably makes it worse. Also the full feathering exercises the seals more on mine.  As a result I had a reseal done early this year at a Hartzell Service Center using NYCO GN3058.

In January 2020 Hartzell completely discontinued use of all AeroShell products and started shipping all new props exclusively with NYCO GN3058.  It is synthetic and NOT COMPATIBLE with AeroShell.  The props have a placard that warn your A&P - if they burp it with crap AeroShell they will be paying for a complete reseal.

 

 

 

Edited October 2, 2022 by 1980Mooney

[DXB]

8 minutes ago, 1980Mooney said:

 

 

In January 2020 Hartzell completely discontinued use of all AeroShell products and started shipping all new props exclusively with NYCO GN3058.  It is synthetic and NOT COMPATIBLE with AeroShell.  The props have a placard that warn your A&P - if they burp it with crap AeroShell they will be paying for a complete reseal.

 

Thanks- important info - when my inevitable IRAN/reseal job happens in the next few years, I gotta make sure it gets NYCO GN3058 and serviced with that going forward.  Ah - and I forgot I'd posted the pic you found of my prop when it first started leaking liquifying #6.  It's been serviced with #5 for 3 years now with reduction (but not cessation) of the leakage since then, and I'm convinced there's plenty of goop inside the hub, so I don't feel urgency to pull the prop off for this reason.

[Shadrach]

@1980Mooney Overservicing aluminum hub Hartzells was an issue long before the Aeroshell 6 reformulation. Servicing an Aluminum hub in the same manner as a steel hub will blow out seals. It might take a few tries but it’s inherent to the design. Aeroshell 6 sucks in my opinion. Even when stored in my hangar fridge, it still separates over time. However, that does not mean it’s the only reason for a hub leak. Not every leak is an Aeroshell 6 issue.  The leak may or may not be due to the new formulation. My prop is full of the new formulation and is oil…er uh…grease tight. I am 5 years SPOH. I thought it was leaking shortly after overhaul but it was just that some residual grease under the plastic zerk cap had separated in the heat.

  

[Shadrach]

26 minutes ago, DXB said:

Thanks- important info - when my inevitable IRAN/reseal job happens in the next few years, I gotta make sure it gets NYCO GN3058 and serviced with that going forward.  Ah - and I forgot I'd posted the pic you found of my prop when it first started leaking liquifying #6.  It's been serviced with #5 for 3 years now with reduction (but not cessation) of the leakage since then, and I'm convinced there's plenty of goop inside the hub, so I don't feel urgency to pull the prop off for this reason.

The prop shop won’t have it any other way. They hav been inundated with reseals over the last several years. I would recommend you IRAN well before you get close to calendar time.  My shop (East Coast Propeller) refused to IRAN my prop at 9 years and 650SPOH.  They will no longer IRAN/reseal props within certain window of calendar TBO.  I as told that the policy was driven by liability concerns.

[DXB]

8 minutes ago, Shadrach said:

The prop shop won’t have it any other way. They hav been inundated with reseals over the last several years. I would recommend you IRAN well before you get close to calendar time.  My shop (East Coast Propeller) refused to IRAN my prop at 9 years and 650SPOH.  They will no longer IRAN/reseal props within certain window of calendar TBO.  I as told that the policy was driven by liability concerns.

Interesting info - East Coast Propeller is the reputable choice around here locally and probably where I would have sent it - I'm past 10 years so probably looking at an overhaul unless I can find another reputable place to IRAN.  I'm probably going to wait a year or two and do it at the same time as my engine. It's nice to work this stuff out in advance and avoid surprises when the time comes.

[1980Mooney]

1 hour ago, Shadrach said:

@1980Mooney Overservicing aluminum hub Hartzells was an issue long before the Aeroshell 6 reformulation. Servicing an Aluminum hub in the same manner as a steel hub will blow out seals. It might take a few tries but it’s inherent to the design. Aeroshell 6 sucks in my opinion. Even when stored in my hangar fridge, it still separates over time. However, that does not mean it’s the only reason for a hub leak. Not every leak is an Aeroshell 6 issue.  The leak may or may not be due to the new formulation. My prop is full of the new formulation and is oil…er uh…grease tight. I am 5 years SPOH. I thought it was leaking shortly after overhaul but it was just that some residual grease under the plastic zerk cap had separated in the heat.

No doubt many props have been either overserviced or poorly/improperly serviced during their life.  No one said every leak is an AeroShell issue.  But it is a serious enough issue that Hartzell publicized the formulation issue in letters to owners/shops and abandoned AeroShell completely - they surely have good reason.  All I know is that during the 21 years of life of my Hartzell Scimitar, it has only been repaired by Texas Aircraft Propellor (formerly R&D Propellor) in Pearland, TX - a certified Hartzell Service Center.  My Scimitar went 14 years without seal leaks before its first overhaul in 2015.  The same A&P shop serviced my prop annually for 9 years before the 2015 overhaul and the 6 years after.  Seal leaks developed the 6th year after the overhaul.  They only known material thing that changed was the formulation of AeroShell 6 at the time of the overhaul.  

Edited October 2, 2022 by 1980Mooney

[bmcconnaha]

1 hour ago, A64Pilot said:

The common practice of keep pumping until it comes out the other side IS the correct procedure for the larger turbine props, I would always pump until I got fresh grease out, took 15 or 20 pumps sometimes but I wanted to flush out all the old grease. Sometimes you would have to pump several pumps before it started coming out the other side.

However it is NOT correct for our smaller piston props and you can overfill the hub, often the symptom of overfilled is a prop that’s slow to cycle.

Make sure whoever is doing it that you don’t flush these little props.

Mine was "flushed" this year on accident.  Issue with the grease gun.  Ended up with more grease in it than I wanted.   Have not flown it since, still finishing the annual.  Hopefully it's no big deal, but I should probably be prepared to have it pulled off and cleaned out  year old  two blade top prop 

[Shadrach]

4 minutes ago, bmcconnaha said:

Mine was "flushed" this year on accident.  Issue with the grease gun.  Ended up with more grease in it than I wanted.   Have not flown it since, still finishing the annual.  Hopefully it's no big deal, but I should probably be prepared to have it pulled off and cleaned out  year old  two blade top prop 

This happened to me many years ago. Mechanic kept pumping until he saw fresh grease. I started to get grease on the windshield within a few minutes of the first post annual run up. Seals likely herniated the first time I cycled the prop. My Prop shop reasealed it gratis as it was just overhauled the year before. I picked the prop up myself and Randy (RIP), the manager at East Coast Propeller gave me a full tour of the shop and a detailed explanation of what had happened. He also gave me a copy of an article from AMT Magazine (IIRC) about over servicing aluminum Hartzells. I gave the article to the IA who serviced the prop. He was initially defensive but was less so after a reasoned discussion (still think of him as a good option for mx). 

[Shadrach]

43 minutes ago, 1980Mooney said:

No doubt many props have been either overserviced or poorly/improperly serviced during their life.  No one said every leak is an AeroShell issue.  But it is a serious enough issue that Hartzell publicized the formulation issue in letters to owners/shops and abandoned AeroShell completely - they surely have good reason.  All I know is that during the 21 years of life of my Hartzell Scimitar, it has only been repaired by Texas Aircraft Propellor (formerly R&D Propellor) in Pearland, TX - a certified Hartzell Service Center.  My Scimitar went 14 years without seal leaks before its first overhaul in 2015.  The same A&P shop serviced my prop annually for 9 years before the 2015 overhaul and the 6 years after.  Seal leaks developed the 6th year after the overhaul.  They only known material thing that changed was the formulation of AeroShell 6 at the time of the overhaul.  

Yes, this should all be common knowledge by now. As should the over service issue. Yet props are still getting overserviced. Ask your favorite prop shop about whether they think field servicing the hub extends the life of any of the components. In my experience, what they’ll say off record and what they’ll say on record or in writing are two different things. These are plain bearings (not hydrodynamic or hydrostatic), Metal to metal contact is part of the design. All the lubricant does is reduce friction.

[Shadrach]

1 hour ago, DXB said:

Interesting info - East Coast Propeller is the reputable choice around here locally and probably where I would have sent it - I'm past 10 years so probably looking at an overhaul unless I can find another reputable place to IRAN.  I'm probably going to wait a year or two and do it at the same time as my engine. It's nice to work this stuff out in advance and avoid surprises when the time comes.

ECP OH was so reasonable, I just went with the OH. I think I paid ~$1700 in 2017 and they picked it up and delivered it to my hangar. Randy told me it has enough blade left for at least one more overhaul.

[bmcconnaha]

2 hours ago, Shadrach said:

This happened to me many years ago. Mechanic kept pumping until he saw fresh grease. I started to get grease on the windshield within a few minutes of the first post annual run up. Seals likely herniated the first time I cycled the prop. My Prop shop reasealed it gratis as it was just overhauled the year before. I picked the prop up myself and Randy (RIP), the manager at East Coast Propeller gave me a full tour of the shop and a detailed explanation of what had happened. He also gave me a copy of an article from AMT Magazine (IIRC) about over servicing aluminum Hartzells. I gave the article to the IA who serviced the prop. He was initially defensive but was less so after a reasoned discussion (still think of him as a good option for mx). 

Well, I'm hopefully going to get it off jacks tomorrow after I check the gear door rigging and do a run up.  If not, in the next day or two after that.  Mine didn’t seem to have much grease in it from the factory, and there was quite a bit of air that came out when I took the plug out of one side.  I assume I’ll know rather quickly if the prop cycle is sluggish and if there is grease on the windshield? 

[Andy95W]

FWIW, I’ll throw out another data point. For the record, I do currently follow the SB and I do not overservice Hartzell propellers.

Both shops that I worked at in the 1990s would grease propellers the same way you would grease any other component- pump grease until you started seeing fresh grease coming out (after removing the opposite side zerk, of course).  That’s a lot of grease, way more than 1 oz.  And that’s how we did all of them, and never heard of a problem until the service bulletin came out.  And between those shops, the A&Ps who worked there like me, and those of us who went on to be IAs, that’s a LOT of annual inspections.  And we never heard of any problems.

Again, I’d not do that now because I realize it’s not necessary and because of the SB.  But I also wouldn’t worry too much unless it shows itself to be a problem.

Edit- the only problem we ever saw was if the mechanic forgot to remove the opposite side zerk fitting. Then the customer would come back with the same situation that Ross described.  

Edited October 2, 2022 by Andy95W

[Guest]

49 minutes ago, Andy95W said:

FWIW, I’ll throw out another data point. For the record, I do currently follow the SB and I do not overservice Hartzell propellers.

Both shops that I worked at in the 1990s would grease propellers the same way you would grease any other component- pump grease until you started seeing fresh grease coming out (after removing the opposite side zerk, of course).  That’s a lot of grease, way more than 1 oz.  And that’s how we did all of them, and never heard of a problem until the service bulletin came out.  And between those shops, the A&Ps who worked there like me, and those of us who went on to be IAs, that’s a LOT of annual inspections.  And we never heard of any problems.

Again, I’d not do that now because I realize it’s not necessary and because of the SB.  But I also wouldn’t worry too much unless it shows itself to be a problem.

Edit- the only problem we ever saw was if the mechanic forgot to remove the opposite side zerk fitting. Then the customer would come back with the same situation that Ross described.  

Most of us were taught the same greasing method, I don’t recall issues with this method.  But now like almost everyone, we grease very little.  During the mandated 10 year overhaul we have the grease changed from Aeroshell.

[A64Pilot]

13 hours ago, Andy95W said:

FWIW, I’ll throw out another data point. For the record, I do currently follow the SB and I do not overservice Hartzell propellers.

Both shops that I worked at in the 1990s would grease propellers the same way you would grease any other component- pump grease until you started seeing fresh grease coming out (after removing the opposite side zerk, of course).  That’s a lot of grease, way more than 1 oz.  And that’s how we did all of them, and never heard of a problem until the service bulletin came out.  And between those shops, the A&Ps who worked there like me, and those of us who went on to be IAs, that’s a LOT of annual inspections.  And we never heard of any problems.

Again, I’d not do that now because I realize it’s not necessary and because of the SB.  But I also wouldn’t worry too much unless it shows itself to be a problem.

Edit- the only problem we ever saw was if the mechanic forgot to remove the opposite side zerk fitting. Then the customer would come back with the same situation that Ross described.  

I overserviced my Hartzell 3 blade on my Maule when it was a new prop, I did it just like we did the turbine props, pumped until I got fresh grease. It did take a lot of grease before it flowed through, but it does on new turbine props too, on the turbines I wouldn’t grease them until after run up for centripetal force to pack the grease and some blades took so much grease that I wouldn’t balance the props until after greasing them.

Anyway I never had a problem with the Maule prop.

Oh and grease coming out of the seals on new turbine props is OK, even getting flecks on the windshield, it will go away after a few hours.

So if your getting some grease on the blades right after greasing the prop I wouldn’t immediately do anything, unless of course it’s a lot of grease

Hartzell’s help desk is a probably better source of info, if you have any questions give them a call. It’s my understanding the grease is largely there as a corrosion preventative, seems I guess during overhaul a lot of props are scrapped from corrosion.