B2Spirit96

M20K 252 Propeller Won't Cycle

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As they say, things can always get worse. On the heels of working a cowl flap motor issue which is now in overhaul, I may have one even worse.

Back story: In Dec, I had a momentary buzz from the prop while in the pattern. It happened very quickly before I could really notice any other indications. I chalked it up to turbulence and being that it was my last pattern, landed without further incident. A week later, shortly after takeoff and turning to downwind, it buzzed again and the RPM spiked to 2800. I turned base and landed. My A&P removed the prop governor and sent it to Palm Beach to be overhauled. I flew 4 flights since then without incident. However, on pre-flight checks for the 5th flight, it would not cycle. I tried numerous times at 1700 and 1800 RPM. Further, with my A&P on board, we tried several times at even higher RPM and still wouldn't cycle. He removed the prop governor again and sent it back to the repair facility. They suspected a sticky valve, replaced, bench-tested good and sent back. After re-installation, it still will not cycle. Working with the Palm Beach facility, they've run several tests to assure oil is flowing to the governor, but it appears pressure to the governor from the crankshaft is fairly low. The current assessment is that the crankshaft bearing controlling pressure to the governor is worn/failed. Worse, it requires an overhaul as a result. His telephone consult with Don George Aircraft in Orlando confirmed the same.

The engine is a Continental TSIO 360 MB with about 1000 hr SMOH. It has normal compressions, oil pressure and runs smooth. My last oil change/sample was clean. I baby the prop the way my instructor (previous owner) taught me. I don't understand why/how it could have failed.

What could we be missing? Anyone else experience a similar issue? I appreciate any advice before spending $50,000 on an otherwise perfectly running engine.

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A quick review of everything related to oil pressure inside the engine... find the drawings... more recent POHs have the drawings... Consider each point where oil can get out... list the good ones that don’t require an engine OH... and the bad ones that would require opening the case to fix.....

keep in mind that there are two separate paths for oil pressure... the one we are discussing here is the oil pressure generated by the gov that gets delivered to the prop... the gov has its own gear pump, and pressure control valve...

Since it happened, fixed itself, and happened again... that is a challenge too...

If you change the oil and find bearing bits and high metals contents in the analysis, that is a hint... of a big, but different problem...

An example of a similar strange behavior is the shaft seal inside the crank opposite of the prop... when this seal stops working, it dumps the oil pressure and oil back into the case... the prop fails to high rpm... from my own O360 experience...

The owner/pilot is left testing everything... expecting the gov to be the culprit... turns out the 50 cent seal inside the shaft, behind the prop needs to be replaced/ re-set... total cost... a few hours to R&R the prop... and reset the 50 cent seal...

There are procedures that can be followed to externally pressurize the system to see what is working or not working...

I learned about this from my friend who built a Long EZ... the EAA guys know some intricate engine phenomena and are really good at sharing too...

We also know a couple of people from Continental that may be helpful with some guidance on how to find out what is going on...

Might be time to change the oil... keeping both eyes wide open when cutting the filter apart...

Good luck with finding what is going on...

We know a guy... a 252 owner and prop guy.... can you feel the rays of sunshine breaking through the clouds?

see if @Cody Stallings is around to gather ideas related to 252 gov failure to control rpm...

PP thoughts only, not a mechanic...

Best regards,

-a-

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2 hours ago, carusoam said:

An example of a similar strange behavior is the shaft seal inside the crank opposite of the prop... when this seal stops working, it dumps the oil pressure and oil back into the case... the prop fails to high rpm... from my own O360 experience...

The owner/pilot is left testing everything... expecting the gov to be the culprit... turns out the 50 cent seal inside the shaft, behind the prop needs to be replaced/ re-set... total cost... a few hours to R&R the prop... and reset the 50 cent seal...

There are procedures that can be followed to externally pressurize the system to see what is working or not working...

 

All good info. The quoted part more accurately describes what I believe has happened. I'm told replacing the shaft seal for this engine is not as simple as R&R the prop and replacing the 50 cent seal. That would be awesome. I appreciate you sharing with the experts for more advice!

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There is no oil governor transfer collar in the 360 as there is in some other engines.  I find it hard to believe that the front bearing is worn enough that the propeller governor can’t control the prop, yet the engine has good oil pressure.  Do you have a friend with the same engine who would let you borrow his governor?

Clarence

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10 hours ago, carusoam said:

A quick review of everything related to oil pressure inside the engine... find the drawings... more recent POHs have the drawings... Consider each point where oil can get out... list the good ones that don’t require an engine OH... and the bad ones that would require opening the case to fix.....

keep in mind that there are two separate paths for oil pressure... the one we are discussing here is the oil pressure generated by the gov that gets delivered to the prop... the gov has its own gear pump, and pressure control valve...

Since it happened, fixed itself, and happened again... that is a challenge too...

If you change the oil and find bearing bits and high metals contents in the analysis, that is a hint... of a big, but different problem...

An example of a similar strange behavior is the shaft seal inside the crank opposite of the prop... when this seal stops working, it dumps the oil pressure and oil back into the case... the prop fails to high rpm... from my own O360 experience...

The owner/pilot is left testing everything... expecting the gov to be the culprit... turns out the 50 cent seal inside the shaft, behind the prop needs to be replaced/ re-set... total cost... a few hours to R&R the prop... and reset the 50 cent seal...

There are procedures that can be followed to externally pressurize the system to see what is working or not working...

I learned about this from my friend who built a Long EZ... the EAA guys know some intricate engine phenomena and are really good at sharing too...

We also know a couple of people from Continental that may be helpful with some guidance on how to find out what is going on...

Might be time to change the oil... keeping both eyes wide open when cutting the filter apart...

Good luck with finding what is going on...

We know a guy... a 252 owner and prop guy.... can you feel the rays of sunshine breaking through the clouds?

see if @Cody Stallings is around to gather ideas related to 252 gov failure to control rpm...

PP thoughts only, not a mechanic...

Best regards,

-a-

I would have the Propeller Cycled on a table.

Actuate it with air to see if it is doing what it is supposed to do.

If you were to pull your Propeller knob all the way out, can you cycle your blades by hand?

Its not easy, but doable.

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I was going to suggest borrow a prop and a govenor - install and test before doing anything invasive.  

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A while ago, I was helping a mechanic pull a prop off a ‘K’. ( not mine). When the prop was removed, there was a lot of what looked like lead paste inside the flange. I guess from centrifugal action. I’m guessing that it could get into the workings of the prop and gum things up. 

Id pull the prop and take a look before I’d do anything else. 

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If you wanted to handle some To/From Shipping cost, I would have no Problem Bench checking your Propeller Per Bono.

Take longer to get it out of a box than to check the Prop Out.

The buzzing your talking about is a little scary.

Was talking with a MU-2 driver that was talking about a Buzzing type of resonance through the aircraft an certain power settings. He ended up having a blade that had slipped in the clamp allowing a fairly large blade angle differential between the blades. You maybe experienceing something similar. I would definitely get it checked out soon.

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What governor do you have, and when was it overhauled? I had mine done early last year, and then got hit by McCauley ASB273B, so it had to come off again and be re-worked. The symptoms I had weren't the same as yours (I got occasional surging - mainly in a go-around situation), but worth checking I suggest

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@B2Spirit96,

Making any headway with your prop challenge?

The buzzing needs some better explanation...

Sounds like the prop needs some attention.  Not so much the engine... (good news, in terms of costs...)

Props have various ways of calling for attention...

Best regards,

-a-

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4 hours ago, carusoam said:

@B2Spirit96,

Making any headway with your prop challenge?

The buzzing needs some better explanation...

Sounds like the prop needs some attention.  Not so much the engine... (good news, in terms of costs...)

Props have various ways of calling for attention...

Best regards,

-a-

Thanks for the follow-up. Work has kept me busy the past couple of days, so no real progress except to collect possible leads. I'm generating a list now from ideas gathered here and plan to discuss with my A&P tomorrow & also see what he has learned. I'm hopeful it is the prop. I like the idea of finding a working governor/prop to try with my engine but don't know of local leads at this moment. I don't know if its possible to lease them for a couple days but am willing to go that route if necessary.

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17 hours ago, Awful_Charlie said:

What governor do you have, and when was it overhauled? I had mine done early last year, and then got hit by McCauley ASB273B, so it had to come off again and be re-worked. The symptoms I had weren't the same as yours (I got occasional surging - mainly in a go-around situation), but worth checking I suggest

I'll have to get back with part details. It was just overhauled in Dec. I flew 4 uneventful flights with it before having the current issue in Jan. It was removed again, essentially overhauled again, bench-checked, and reinstalled. Still not working. The surging (buzzing) did occur while either adding power on missed approach from instrument pattern or at full power on initial takeoff. I'll follow up on the ASB if applicable.

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I would put a pressure gauge on the governor line.  If it reads right then you know you issue is either the prop (most likely) or the case (less likely).  

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18 hours ago, Cody Stallings said:

If you wanted to handle some To/From Shipping cost, I would have no Problem Bench checking your Propeller Per Bono.

Take longer to get it out of a box than to check the Prop Out.

The buzzing your talking about is a little scary.

Was talking with a MU-2 driver that was talking about a Buzzing type of resonance through the aircraft an certain power settings. He ended up having a blade that had slipped in the clamp allowing a fairly large blade angle differential between the blades. You maybe experienceing something similar. I would definitely get it checked out soon.

Cody, thank you! It's in my A&P hangar, not flying while we sort this out. I'll PM my contact info and perhaps get a second opinion from you on the bench check.

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1 minute ago, M20F said:

I would put a pressure gauge on the governor line.  If it reads right then you know you issue is either the prop (most likely) or the case (less likely).  

I'll share with my A&P tomorrow. I think he's done this, but worth revisiting to be sure. He's a great A&P, but this has been a challenging problem to resolve. Together, we're canvassing the community to be sure we've looked at everything correctly. Thanks for your recommendation.

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A recent example of a strange Mooney/prop issue comes from MSer @jcovington...

his prop thread opens your eyes to things that can go awry with just the prop...

Best regards,

-a-

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8 minutes ago, carusoam said:

A recent example of a strange Mooney/prop issue comes from MSer @jcovington...

his prop thread opens your eyes to things that can go awry with just the prop...

Best regards,

-a-

Great article! I'm going to look a little closer at my prop tomorrow as well!

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On 2/18/2019 at 4:25 PM, jackn said:

A while ago, I was helping a mechanic pull a prop off a ‘K’. ( not mine). When the prop was removed, there was a lot of what looked like lead paste inside the flange. I guess from centrifugal action. I’m guessing that it could get into the workings of the prop and gum things up. 

Id pull the prop and take a look before I’d do anything else. 

Jack, we're going to look at the prop closer. Thanks for your insight.

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On 2/18/2019 at 2:44 AM, bradp said:

I was going to suggest borrow a prop and a govenor - install and test before doing anything invasive.  

Sounds easy. I don't know who to ask but will check around. I'll see who my A&P might know locally.

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On 2/17/2019 at 11:00 AM, B2Spirit96 said:

As they say, things can always get worse. On the heels of working a cowl flap motor issue which is now in overhaul, I may have one even worse.

Back story: In Dec, I had a momentary buzz from the prop while in the pattern. It happened very quickly before I could really notice any other indications. I chalked it up to turbulence and being that it was my last pattern, landed without further incident. A week later, shortly after takeoff and turning to downwind, it buzzed again and the RPM spiked to 2800. I turned base and landed. My A&P removed the prop governor and sent it to Palm Beach to be overhauled. I flew 4 flights since then without incident. However, on pre-flight checks for the 5th flight, it would not cycle. I tried numerous times at 1700 and 1800 RPM. Further, with my A&P on board, we tried several times at even higher RPM and still wouldn't cycle. He removed the prop governor again and sent it back to the repair facility. They suspected a sticky valve, replaced, bench-tested good and sent back. After re-installation, it still will not cycle. Working with the Palm Beach facility, they've run several tests to assure oil is flowing to the governor, but it appears pressure to the governor from the crankshaft is fairly low. The current assessment is that the crankshaft bearing controlling pressure to the governor is worn/failed. Worse, it requires an overhaul as a result. His telephone consult with Don George Aircraft in Orlando confirmed the same.

The engine is a Continental TSIO 360 MB with about 1000 hr SMOH. It has normal compressions, oil pressure and runs smooth. My last oil change/sample was clean. I baby the prop the way my instructor (previous owner) taught me. I don't understand why/how it could have failed.

What could we be missing? Anyone else experience a similar issue? I appreciate any advice before spending $50,000 on an otherwise perfectly running engine.

How is the investigation going?

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