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Do I need to pull my prop?


Guest Spike Kavalench

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Guest Spike Kavalench

So I had the engine overhauled because of a main bearing chewing itself up. We overhauled the prop governor, replaced all the oil hoses and oil cooler, but after flying it two hours I find out the mechanic only flushed the prop and did not send it for a contamination inspection. We’re doing the annual now and my current mechanic thinks the prop should be sent in for a contamination inspection.  The prop still has two years on it before it needs a 10 year overhaul (Canadian requirement).

Do I need to pull the prop and have it opened up?

Also my spinner is cracked so I may have to pull the prop anyway to replace the backing plate if I can’t find a spinner to fit that one. So... prop prolly has to come off regardless. Sent ACPartswharehouse a message but if anyone has a tagged spinner for sale I’m interested. (1961 M20 B with 2 blade Hartzel HC-C2YK-1BF.)

Spike

 

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1 hour ago, Spike Kavalench said:

So I had the engine overhauled because of a main bearing chewing itself up. We overhauled the prop governor, replaced all the oil hoses and oil cooler, but after flying it two hours I find out the mechanic only flushed the prop and did not send it for a contamination inspection. We’re doing the annual now and my current mechanic thinks the prop should be sent in for a contamination inspection.  The prop still has two years on it before it needs a 10 year overhaul (Canadian requirement).

Do I need to pull the prop and have it opened up?

Also my spinner is cracked so I may have to pull the prop anyway to replace the backing plate if I can’t find a spinner to fit that one. So... prop prolly has to come off regardless. Sent ACPartswharehouse a message but if anyone has a tagged spinner for sale I’m interested. (1961 M20 B with 2 blade Hartzel HC-C2YK-1BF.)

Spike

 

I would be very...very...very....very....surprised if contaminates made it to the prop hub. I’m betting that your previous mechanic had a better understanding of how a CS Propeller works and that is why he elected to simply flush the hub.

Edited by Shadrach
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If the prop is coming off anyhow, may as well send it for OH. I know, 2 years down the tubes. But, if it gives you peace of mind, the get it done. Preventative maintenance. 

Just took mine off tonight for its 10 year OH

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14 minutes ago, carusoam said:

Let’s see if MS’s prop guy is around for some insight... @Cody Stallings  ^^^^

Best regards,

-a-

I have found very little metal in a regular Constant Speed Prop.

There is just so little oil movement with 0(Zero) circulation.

You see some metal in Feathering props, an reversible props cause there is much more oil Movement.

 

I would probably want to atleast have the cylinder flushed just to get the ol sludge out. That’s a $400 of piece of mind in my shop.

Certaily wouldn’t O/H it.

Its only going to O/H so many times, but you can flush the Hydraulic unit anytime you want.

My 2 Pennies 

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5 minutes ago, Cody Stallings said:

I have found very little metal in a regular Constant Speed Prop.

There is just so little oil movement with 0(Zero) circulation.

You see some metal in Feathering props, an reversible props cause there is much more oil Movement.

 

I would probably want to atleast have the cylinder flushed just to get the ol sludge out. That’s a $400 of piece of mind in my shop.

Certaily wouldn’t O/H it.

Its only going to O/H so many times, but you can flush the Hydraulic unit anytime you want.

My 2 Pennies 

Thank you for being so honest Cody. The willingness of people to throw money at things for which they have no understanding means that you could make a fortune acting in a less virtuous manner.  You’re a credit to your profession and a great asset to this community.

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Guest Spike Kavalench
55 minutes ago, GLJA said:

If the prop is coming off anyhow, may as well send it for OH. I know, 2 years down the tubes. But, if it gives you peace of mind, the get it done. Preventative maintenance. 

Just took mine off tonight for its 10 year OH

Thanks for all the input guys. I guess we’ll pull it and have a prop shop flush the hub. Cheers! 

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44 minutes ago, Spike Kavalench said:

Thanks for all the input guys. I guess we’ll pull it and have a prop shop flush the hub. Cheers! 

Wait, didn’t your previous mechanic already do that? For the purpose of this discussion, your CS prop is a hydraulically actuated piston. The piston is actuated by varying the pressure in the line (external line running from the governor to the front of the case). There is no means for oil (nor particulate) to circulate through the hub. The oil in there now is the same oil that filled the hub the first time you ran the engine. That oil will remain in the hub until the prop is removed. I’m wondering what you think a second flush will accomplish?

Edited by Shadrach
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Guest Spike Kavalench

Seems logicsl... the previous mechanic didn’t disassemble anything, he just flushed it from the outside, I presume...thanks for your input.

 

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Wait, didn’t your previous mechanic already do that? For the purpose of this discussion, your CS prop is a hydraulically actuated piston. The piston is actuated by varying the pressure in the line (external line running from the governor to the front of the case). There is no means for oil (nor particulate) to circulate through the hub. The oil in there now is the same oil that filled the hub the first time you ran the engine. That oil will remain in the hub until the prop is removed. I’m wondering what you think a second flush will accomplish?

Since we run fresh engines on straight mineral oil, you’re saying it stays in there for years? I’d be surprised if the oil didn’t drain out on engine shutdown?


Tom
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First thing, what did your engine overhauled say about oil system cleaning?  Many will have a clause about warranty denial if the oil system wasn’t decontaminated.  Hate to lose a warranty claim over not doing the prop.

Secondly, If there is no oil flow through the prop from the governor and the oil in the hub is the same oil from the original start, in this case clean mineral oil, can someone please explain to me how all the sludge appears in the crankshaft bore when I pull a propeller?

Clarence

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1 hour ago, ArtVandelay said:


Since we run fresh engines on straight mineral oil, you’re saying it stays in there for years? I’d be surprised if the oil didn’t drain out on engine shutdown?


Tom

Be surprised...or better yet, go look at how your governor is plumbed. The oil in the hub would need to defy gravity.

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I would think that Cycling the prop from fine to course and back to fine would move some oil into and then back out of the piston chamber in the hub, the oil coming back out would mix with the engine oil and then a new unit of oil would be sent into the hub the next cycle.  I agree that some oil is always in the hub but I think there is a portion being replaced on each cycle however small a portion that may be.  My prop governor (TSIO360) is mounted up front on the case snout so there isn't a very large quantity of oil in the entire "Propeller Oil System".

 

Ron

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23 hours ago, Marcopolo said:

I would think that Cycling the prop from fine to course and back to fine would move some oil into and then back out of the piston chamber in the hub, the oil coming back out would mix with the engine oil and then a new unit of oil would be sent into the hub the next cycle.  I agree that some oil is always in the hub but I think there is a portion being replaced on each cycle however small a portion that may be.  My prop governor (TSIO360) is mounted up front on the case snout so there isn't a very large quantity of oil in the entire "Propeller Oil System".

 

Ron

Negative. The volume of oil in the hub is pretty small and the travel of the piston short. For a Hartzell aluminum hub, think baby food jar quantities to actuate  from fine to course. The volume of oil in the line feeding the prop exceeds the volume actuating the piston. 

Post edited for due to poor wording...

Edited by Shadrach
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11 minutes ago, Shadrach said:

Negative. The volume of oil in the hub is pretty small and the travel of the piston short. For a Hartzell aluminum hub, think baby food jar quantities. The volume of oil in the line feeding the prop exceeds the volume in the hub.

Understood on the size of the chamber in the hub, I add to that the size of the chamber in the crankshaft.  I have no oil line between my governor and the hub so even a small displacement "may" exchange some oil.  I'm with Clarence ( @M20Doc ) on this one.  Some oil must be moving through this system as there is always a sludge build up within the crankshaft chamber from centrifugal force when I remove a prop, even on IO-360s I see this build up.  A baby jar's worth of oil should not leave a noticeable amount of residue behind if never circulated, unless the sludge is created from something else.  I'm learning here so please don't take this as anything more.

 

Ron

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On 3/6/2019 at 11:38 AM, Marcopolo said:

Understood on the size of the chamber in the hub, I add to that the size of the chamber in the crankshaft.  I have no oil line between my governor and the hub so even a small displacement "may" exchange some oil.  I'm with Clarence ( @M20Doc ) on this one.  Some oil must be moving through this system as there is always a sludge build up within the crankshaft chamber from centrifugal force when I remove a prop, even on IO-360s I see this build up.  A baby jar's worth of oil should not leave a noticeable amount of residue behind if never circulated, unless the sludge is created from something else.  I'm learning here so please don't take this as anything more.

 

Ron

Our resident prop shop owner has clearly stated what I’ve said above as fact. It ruffled some feathers when I said it the first time which is why I asked him to clarify...  

It’s not like uh, my opinion man.

The total volume of the prop control system and hub when compared to the amount of fluid (oil) required to move the piston from the fine pitch stops to course pitch is small. Again, think baby food jar. 

Aviation is full of half truths and OWTs that have grown out of misunderstandings passed down from our tribal leaders. I started flying before we had internet. In those days, everyone just assumed anything uttered by the “Ace of the Base” was correct. We are so fortunate now to have access to a community that is a concentrated source of type specific information. Nevertheless, I speak from experience when I say it’s hard to let go of a hard won misunderstanding!

So...

Go pull that prop through by hand before start up to “distribute the oil”.

Cycle the prop at least 3 times before take off to get “fresh warm oil to the hub”.

Keep her “under square” in the climb.

Be sure to overshoot your cruise alt by 50’ or so to help you get “on the step”

Do keep the power up in descent to avoid “shock cooling”

Don’t do forward slips in a Mooney and definitely don’t do any “slips with flaps”.

Don’t do touch and gos, every time you do a cute little puppy dies.

And for god’s sake be ready to almost lose control of the plane if you abort a landing with full flaps.   When you go full power it will stand straight up like an Extra 300 in an airshow.

I’m sure I’ve missed a few so feel free to pick up where I left off...;):P

 

 

Edited by Shadrach
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12 minutes ago, Shadrach said:

Aviation is full of half truths and OWTs that have grown out of misunderstandings passed down from our tribal leaders.

Ross,  

 

  You quoted me in your response so I can't help but assume the insult that I'm following some sort of OWT was directed at me!  I stated what I understand of the system and what I don't understand of the system, nothing more.   I understand that very little oil resides in the entire prop pitch control system, I don't understand how that small amount of oil puts out a generous quantity of residue from centrifugal filtering.  I expressed my only logical explanation for how more oil may pass through this centrifugal filtering to contribute to the deposits.  I am not questioning Cody ( @Cody Stallings) or anyone else, as stated, I'm learning and am simply looking for the answer to a question that was asked previously to when I regurgitated it.

 

  I'll let it go for now, books don't fight back...often!  I'll go read up learn what I can.  Please keep the information coming as I learn from and can count on it for the most part.

 

Ron

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10 minutes ago, Marcopolo said:

 

Ross,  

 

  You quoted me in your response so I can't help but assume the insult that I'm following some sort of OWT was directed at me!  I stated what I understand of the system and what I don't understand of the system, nothing more.   I understand that very little oil resides in the entire prop pitch control system, I don't understand how that small amount of oil puts out a generous quantity of residue from centrifugal filtering.  I expressed my only logical explanation for how more oil may pass through this centrifugal filtering to contribute to the deposits.  I am not questioning Cody ( @Cody Stallings) or anyone else, as stated, I'm learning and am simply looking for the answer to a question that was asked previously to when I regurgitated it.

 

  I'll let it go for now, books don't fight back...often!  I'll go read up learn what I can.  Please keep the information coming as I learn from and can count on it for the most part.

 

Ron

 Ron,

I wasn’t trying to insult anyone. Context gets lost on the internet.  My post was actually meant to be funny. it was sort of directed at our sacred cows. My apologies! :)

An interesting study on the centrifugal filtering would be to have oil analysis performed on a sample of oil from the prop when it’s removed and compare it to oil removed from the crankcase at the same time.

Edited by Shadrach
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31 minutes ago, Shadrach said:

Ron,

I wasn’t trying to insult anyone. Context gets lost on the internet.  My post was actually meant to be funny. it was sort of directed at our sacred cows. My apologies! :)

  My apologies for missing the jest of the post.  I'll admit that I've changed my SOPs based on several posts from this forum, some directly contributed to you and I agree that some people don't care to learn why they do things a certain way or that there could be a better or maybe just a different way.  I'm relatively new to this flying thing but not to engines and aerodynamics.  But the engines I'm used to, some air and some liquid cooled, none had the paddle thing attached to them.  

 Good suggestion on getting an analysis of the sludge as compared with the crankcase oil!

 

Ron

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5 hours ago, Marcopolo said:

I would think that Cycling the prop from fine to course and back to fine would move some oil into and then back out of the piston chamber in the hub, the oil coming back out would mix with the engine oil and then a new unit of oil would be sent into the hub the next cycle.  I agree that some oil is always in the hub but I think there is a portion being replaced on each cycle however small a portion that may be.  My prop governor (TSIO360) is mounted up front on the case snout so there isn't a very large quantity of oil in the entire "Propeller Oil System".

 

Ron

The gist of it is that if the volume of oil in the prop control system is greater than the volume of oil in the hub, the oil in the hub will never change or mix with engine oil.  Part of the oil in the lines WILL be changed/mixed with the main engine oil, but engine oil will only enter up to the volume in the control system that is the same volume as the hub.

Not knowing any specifics, but that means engine oil DOES make it into the prop control system, but only up to a specific point.  I imagine how far it makes it depends on the specific engine/prop combo.

I forget my physiology, but you can see the same thing in the human lung.  If you breathe with short, shallow breaths, there's a point where the volume of each breath is too small and not able to reach the alveoli, so you end up mixing oxygen only in the airways and not where it counts.

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5 minutes ago, jaylw314 said:

The gist of it is that if the volume of oil in the prop control system is greater than the volume of oil in the hub, the oil in the hub will never change or mix with engine oil.  Part of the oil in the lines WILL be changed/mixed with the main engine oil, but engine oil will only enter up to the volume in the control system that is the same volume as the hub.

Not knowing any specifics, but that means engine oil DOES make it into the prop control system, but only up to a specific point.  I imagine how far it makes it depends on the specific engine/prop combo.

I forget my physiology, but you can see the same thing in the human lung.  If you breathe with short, shallow breaths, there's a point where the volume of each breath is too small and not able to reach the alveoli, so you end up mixing oxygen only in the airways and not where it counts.

Really?   Sticking with your human lung analogy, can you tell me what left the sludge in your throat?  That's the question in the end of this, I was only trying to explain out loud how I thought the sludge/deposit was created in the "throat" of the crankshaft.   Ross has given a suggestion to first determine where it came from and that will lend to the next event of determining how that vehicle left it.

 

  I apologize to the OP as I've caused a serious derailment of this thread.  If your previous mechanic took the propeller off and cleaned all visible areas then I believe all the flushing that can be done to the propeller has been done!

 

Ron

  

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20 minutes ago, jaylw314 said:

The gist of it is that if the volume of oil in the prop control system is greater than the volume of oil in the hub, the oil in the hub will never change or mix with engine oil.  Part of the oil in the lines WILL be changed/mixed with the main engine oil, but engine oil will only enter up to the volume in the control system that is the same volume as the hub.

Not knowing any specifics, but that means engine oil DOES make it into the prop control system, but only up to a specific point.  I imagine how far it makes it depends on the specific engine/prop combo.

I forget my physiology, but you can see the same thing in the human lung.  If you breathe with short, shallow breaths, there's a point where the volume of each breath is too small and not able to reach the alveoli, so you end up mixing oxygen only in the airways and not where it counts.

My take exactly.  I've been thinking of how to articulate it but your post is superior to anything I've come up with.

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23 minutes ago, Marcopolo said:

Really?   Sticking with your human lung analogy, can you tell me what left the sludge in your throat?  That's the question in the end of this, I was only trying to explain out loud how I thought the sludge/deposit was created in the "throat" of the crankshaft.   Ross has given a suggestion to first determine where it came from and that will lend to the next event of determining how that vehicle left it.

 

  I apologize to the OP as I've caused a serious derailment of this thread.  If your previous mechanic took the propeller off and cleaned all visible areas then I believe all the flushing that can be done to the propeller has been done!

 

Ron

  

I've been told the sludge is lead.  I've also been told it is part particulate pulled out of solution.  The next person to pull a prop and send it to Blackstone. 

Edit: My buddy just pulled the prop on his Comanche 250 and has yet to clean the flange.  I will clean it for him and send the sludge out for analysis.

Edited by Shadrach
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So, looking at this diagram:
34398912befbeef8cc67ecffbddbfed1.jpg
The oil in the governor is returned to the sump.
The governor boost the oil pressure 3-6 times engine pressure.
When you shut down the engine, the oil in the prop (under high pressure) will return to the governor (not all of it, but certainly some of it), which returns to the engine sump.



Tom

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Just now, Shadrach said:

I've been told the sludge is lead.  I've also been told it is part particulate pulled out of solution.  The next person to pull a prop should send a big glob off to blackstone.

  I've been told the same, and there's the rub.  Stay with me here, I'm only theorizing.  if the only oil that makes it past the crankshaft oil port into the "baby jar" is the first bit of oil it sees then where would all that lead come from.  In order for oil to carry lead there in the quantity I see on a regular basis I would think (opinion) it would have to be replacing a small portion of oil in that baby jar somewhat regularly.  Now I am saying this with absolutely no knowledge of how much oil would have to go through that area to leave how much residue, but to have any lead in the oil (careful here because engine oil could contain a zinc additive) you would think it had been through the engine and picked up lead via blow by from combustion or from the cylinder walls and then run through the governor to that area of the prop/crank and refreshed in small quantities to leave the amounts I see from annual to annual on many different airplanes.  

 

  Again, I'm only trying to figure this out for my own education as I clean this sludge out of more than a few cranks and hubs on a regular basis.  I cycle my prop once during the first run-up of the day just to make sure it works and doesn't spray oil on the windscreen (BTDT).  I do not think cycling the prop three or four times replaces the prop control system with an entire fresh batch of warm oil.  

 

And again my apologies to the OP!

 

Ron

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