Cylinder Failure - M20K-231

[N303FW]

Great forum, glad to have found it.

I've had my 1981 M20K-231 since 2002 and its been a terrific airplane.  I have a factory reman TSIO360LB1 with a turboplus intercooler, gamijectors and a JPI EDM-700.  I generally operate my aircraft ROP along the guidlines outline by Bob Kromer in his Flight Ops article and I'm glad to have found an expert like him to give me guidance.

I had a clyliner go bad last week shortly after takeoff (thankfully, I made a safe return to the airport) and although my mechanic and I've kicked a bunch of ideas around we haven't found anything definitive.  My mechanic said that he's never seen damage like mine - the top of the piston totally melted.  He's sure it was a case of detonation but there is no obvious cause - the injector appears clean, etc.  Our only thought is a stuck valve.  Anyone had a similar experience and/or want to share your thoughts?

I've attached my JPI data for fun.  If you can't open it or see it clearly let me know and I'll e-mail it to you.

Pete

[KLRDMD]

Quote: N303FW

I generally operate my aircraft ROP along the guidlines outline by Bob Kromer in his Flight Ops article and I'm glad to have found an expert like him to give me guidance.

[N303FW]

KLRMDM, thank you for your comment but I'm not quite sure I understand to what you are referring.  LOP operation and its advantages?  Something else?

 

[KLRDMD]

Quote: N303FW

Thank you for your comment but I'm not quite sure I understand to what you are referring.  LOP operation and its advantages?  Something else?

[Jeff_S]

Ken, you've said this about 50° ROP in other places,  but never really explained why you have this opinion. From all my study (and believe me, I've studied) I think you say this because it is the realm where CHTs are hottest and most likely to cause heat-related problems. It also is burning more gas than LOP but without the cooling effect of running 100° ROP.

So to summarize, you're burning more gas (= more $$) but not getting the benefit of more cooling, and yet you're not at full power so you're also not getting the benefit of greater speed. You're kind of getting the worst of both worlds. Is my interpretation of your belief correct?

[N303FW]

I've researched LOP and other engine management techniques, but I've never had a chance to talk to anyone who's really had an oportunity to run their turbo Mooney using these concepts - that's one of the big reasons I'm happy to have found this forum.

I've found ROP cruise keeps my CHT temps below 380degF while keeping decent speed and burning less than 13gal/hr.  I climb 110-120 indicated full rich (up to 10-15k or so), and only really experience higher engine temps in extended climbs over 15k or so.  What technique do you use and kinds of temps do you see?  I'm especially interested in keeping my engine running cool in climbs over 15k.  Anyone found a technique that works?  I'd love to hear more!

 

[KLRDMD]

Quote: Jeff_S

Ken, you've said this about 50° ROP in other places,  but never really explained why you have this opinion. From all my study (and believe me, I've studied) I think you say this because it is the realm where CHTs are hottest and most likely to cause heat-related problems. It also is burning more gas than LOP but without the cooling effect of running 100° ROP.

So to summarize, you're burning more gas (= more $$) but not getting the benefit of more cooling, and yet you're not at full power so you're also not getting the benefit of greater speed. You're kind of getting the worst of both worlds. Is my interpretation of your belief correct?

[KLRDMD]

Quote: N303FW

I've researched LOP and other engine management techniques, but I've never had a chance to talk to anyone who's really had an oportunity to run their turbo Mooney using these concepts - that's one of the big reasons I'm happy to have found this forum. I've found ROP cruise keeps my CHT temps below 380degF while keeping decent speed and burning less than 13gal/hr.  I climb 110-120 indicated full rich (up to 10-15k or so), and only really experience higher engine temps in extended climbs over 15k or so.  What technique do you use and kinds of temps do you see?  I'm especially interested in keeping my engine running cool in climbs over 15k.  Anyone found a technique that works?  I'd love to hear more!

[Kwixdraw]

I'm curious about this piston "melting". That doesn't sound like detonation to me. Not being too familiar with the particular Continental in question, could it be possible that an air leak developed in the  intake plumbing for that cylinder and caused it to go very lean? I couldn't get the graph to enlarge big enough to read it and see if there was an indication there. What do you professional wrench turners think?  

[Cruiser]

It is difficult to see anything on the graph. The EGT and CHT traces are all overlaid. You MAY have been lucky in that it was only one cylinder. What does the fuel flow trace look like?

TomK

[KSMooniac]

Quote: Jeff_S

Ken, you've said this about 50° ROP in other places,  but never really explained why you have this opinion. From all my study (and believe me, I've studied) I think you say this because it is the realm where CHTs are hottest and most likely to cause heat-related problems. It also is burning more gas than LOP but without the cooling effect of running 100° ROP.

So to summarize, you're burning more gas (= more $$) but not getting the benefit of more cooling, and yet you're not at full power so you're also not getting the benefit of greater speed. You're kind of getting the worst of both worlds. Is my interpretation of your belief correct?

[N303FW]

Unfortunately I don't have fuel flow as part of my EDM-700, might try to add it though now.  I've attached a clearer copy of the CHT, EGT, TIT and oil temps graph.  I'm also posting a picture of the piston head after we removed the cylinder - note the melted aluminum and the rounded edges.  Yes, I feel lucky that I didn't lose the whole engine, which incidentally only has ~600 hrs on a factory reman.

Its interesting to note how quickly this happened - it only took about 2 minutes on takeoff to go from ~350degF to over 550degF.

 

 

[KLRDMD]

Quote: N303FW

Unfortunately I don't have fuel flow as part of my EDM-700, might try to add it though now. 

[N303FW]

I've been flying my Mooney coast to coast since 2002 and have had very little difficulty with it using standard ROP techniques.  Course, here I am rethinking my stratagy after a single, albiet major, issue.  Things can happen LOP as well, for instance a buddy of mine burned up a cylinder in his turbo A36 while operating LOP (yes, he was properly trained to operate LOP).  After that everyone in our neck of the woods was questioning LOP operation. 

Its tough to know what the real cause is most of the time, but its fun to try to find out.  I know that everyone holds their opinions dear and it's really interesting hearing about other peoples actual experiences and not simply about theory they read in a magazine - that experience is the key advantage of a forum like this.

I like Scotts idea of the Advanced Pilot Seminar and need to find out more about the class.  Is that through MAPA?

[jlunseth]

No, its through GAMI.  http://www.advancedpilot.com/

They have a course coming up in Ohio in June, I believe.

[KSMooniac]

Pete, check out www.advancedpilot.com The principals of that course are extremely knowledgeable.  One of them (George Braly) is the chief engineer at GAMI/Tornado Alley Turbos.  Usually the course is held in Ada, OK (GAMI facility), but the next live one will be in Dayton...much closer to you.  In Ada you get to witness the concepts "live" on their extremely sophisticated engine test stand, so you literally see why running LOP results in lower peak ICP, lower CHTs, etc.  It is NOT opinion when it can be demonstrated right in front of your eyes.  These guys have done a tremendous amount of research to understand what is going on with our engines, and this course should be required for owners and mechanics IMO.  It is really *that good*!

Regarding "burning up a cylinder," that cannot be attributed to LOP operations.  Running LOP results in cooler cylinders and cooler valves than running ROP, period.  What is more likely is that the valve->seat interface was not done well at the factory, and that led to a premature valve failure if I had to guess without knowing anything about that particular instance.  There was a cost-savings step implemented by TCM years ago that reduced the quality of the valve fits, and as a result, cylinders need work after 600-800 hours, no matter if they're run ROP or LOP.  That is believed to have been corrected in recent history, but only time will tell as the newest jugs accumulate hours.  Lots of folks without the education will attribute failures to LOP just because they don't understand, and that doesn't make it true.  Mechanics are especially bad at this, IMO.

Your case looks to be a detonation event, but I haven't looked at enough of them to say for sure.  I'll bet you a dollar that you could send your monitor data and picture to George Braly or Walter Atkinson and they'll tell you what it was and why it happened, especially if you express an interest in going to their class.

[N303FW]

Terrific info, thanks.

[Parker_Woodruff]

It's hard to read but what are you generally seeing for CHTs at the power settings you've been using?

[The-sky-captain]

Quote: KSMooniac

 I say it every chance I get...every pilot should attend the Advanced Pilot Seminar live class and learn all about this stuff. 

[KLRDMD]

[N303FW]

Quote: Parker_Woodruff

It's hard to read but what are you generally seeing for CHTs at the power settings you've been using?

[N303FW]

Quote: KSMooniac

What is more likely is that the valve->seat interface was not done well at the factory, and that led to a premature valve failure if I had to guess without knowing anything about that particular instance.  There was a cost-savings step implemented by TCM years ago that reduced the quality of the valve fits, and as a result, cylinders need work after 600-800 hours, no matter if they're run ROP or LOP.

[KSMooniac]

Pete, I don't know of any specific documentation that is "out there" in terms of an AD or SB.  It was mentioned in the APS class that I took in 2007, and I've read supporting anecdotal accounts over the years on the AOPA forum.  You'll never get TCM to admit to it, though.  I suspect your cylinders are very likely in the batch that have the issue, though.  You won't be able to inspect anything unfortunately unless you remove the cylinders and check the fit and concentricity of the valve/seat interface.  This was something that was discovered by realizing a sizeable number of TCM cylinders didn't last, no matter how well they were managed, and then performing autopsies when able.  Some unofficial confirmation about changes in the production line/quality control was also learned, and 2+2=4 at the end of the day.  Apparently some shops recognized this as well, and would disassemble brand-new TCM engines, fix the valves, and then install the engine before giving it to the customer just to make sure they got a good one.  Pretty sad... similar to Lycoming farming out fabrication and skipping steps in the heat-treats and inspections.

I would recommend you email Walter Atkinson (find his address on the APS site) and describe your current failure and tell him about your 1999 reman.  You could also express an interest in the Dayton class in June, and ask him if there will be live demos like they do in Ada, or if it will only be classroom work.  He is very gracious with those that are seeking to learn, so I have a hunch he will give you a very good and detailed answer regarding your failure and the likelihood of trouble with your current engine.

Pending an answer from Walter, you might mentally prepare for pulling the remaining jugs and getting a shop to check the valves and grind/fit as necessary...just a hunch on my part.

[FlyingAggie]

While at my pre-buy/annual last week at LASAR, I asked about operating the TSIO360-MB in my new (to me) plane LOP and they said they don't recommend it and that it is particularly hard on valves.  The valve need fuel for cooling.  My plane does have GAMI's and an engine monitor, so in theory I should be ableto run LOP.

So I am undecided at this point, but plan on taking the APS to find more about "the dark side."

 

[KSMooniac]

With all due respect to LASAR, they have no idea what they're talking about with regards to LOP.  Running LOP (correctly) is easier on the engine.  The cylinders are cooler, and the valves are cooler.  Unlike global warming, that is able to be shown on an instrumented engine!  Valves do not need fuel for cooling...that is a misunderstanding of the science.  More fuel when ROP slows down the combustion event, which makes things cooler.  More air when LOP does the same thing!  50 ROP yields the same exhaust temps as 50 LOP, but dramatically cooler cylinders and valves.    Again, running richer when ROP does indeed make the cylinders cooler, but it is not because the fuel is cooling anything!