Turbo Failure mode! Single turbo Vs. Twin or TN?

[kmyfm20s]

29 minutes ago, peevee said:

Yes and no.

 

In our case the turbo ingested something after overhaul. The problem manifested itself about 8 or 10 hours later when the main bearing failed and it plastered the plane with oil and smoke when I went to get fuel for a trip the next day. There was no noise or indication anything was wrong. Had that happened in flight it would have probably lost the crankcase worth of oil pretty quickly with no indication until you started to see a drop in oil pressure. End result could be the same if the engine seized before you found an airport.

 

I had flown the airplane to 17,5 the day before and there was no problem maintaining power and no oil in or dripping from the exhaust before I went for fuel. I always check for a failed check valve and the security of the vband clamps in preflight 

 

We overhauled our turbos at about 1700 hours and main turbo thought they were pretty long in the tooth. It's not just the bearings you have to worry about, the turbine blades get gunked up and blasted and eroded by exhaust gasses too.

I’m assuming it is a common TIT probe for both turbos? It would be nice if there was something that could have indicated one was offline.

[Guest]

5 hours ago, Marcopolo said:

1981 M20K TSIO360 GB(3) Original Engine with 1650hrs since new.  Original Rajay fixed wastegate Turbo! (yikes)

My maintenance routine (as it applies to the Turbo Charger)

 

  Every Pre-Flight includes opening the Turbo inspection panel and visually inspecting the 3 v-band clamps and turbo general condition.  Grabbing the exhaust pipe and moving it to show any looseness and listen for any noises that shouldn't be there.

 

  During oil changes (30hrs) In addition to the above I will run a boroscope up the exhaust pipe to inspect the turbine blades and turbine housing.  I will also remove the air filter and try the wiggle test on the compressor end of the turbine shaft.  I also spin the compressor and check for binding, scraping noises and how freely the shaft spins (it should have very slight resistance, a smooth solid feel).  I apply mouse milk to all exhaust and bypass joints.

 

  At annual inspection in addition to all the above, the turbo may be removed and a more thorough inspection completed to include inspecting the turbine housing for cracks at the inlet area (usually not visible by boroscope through exhaust), Scavenge check valves removed, checked and cleaned, new turbine mating surface gasket installed, replace any suspect v-band clamps (check time or torque cycle replacement requirements).

 

  This is my maintenance routine, I'm posting it so it can be used or critiqued ( @M20Doc please correct any mistakes or fill in any blanks)

 

 Ron

That seems like a successful process, if you’ve made it this far with no issues.  Keep up the good work.

Clarence

Edited May 3, 2018 by M20Doc

[aviatoreb]

8 hours ago, Marauder said:

Erik - I really appreciate your transparency on your thought process through this emergency. Many, many, many owners have flown for years without nothing more than the occasional rough running engine or the infamous “automatic rough” when flying over inhospitable terrain. 

For those who have never experienced an emergency, I hope you never do. For those of us who have, it is hard to express how the survival instinct takes over. 

Erik’s comment about the smell of adrenaline hits home. ...

Be safe out there!

 

It is my pleasure to share since I figure I appreciate when others do so.

One funny thing - I am a scientist for a living - and I find scientific things interesting....  so there I am half way into this thing and concentrating to stay on task and not let the adrenaline and the situation just get away from me, and then somewhere part of my mind was thinking, "gee this adrenaline stuff is quite a powerful hormone - its doing just like its supposed to...I can feel my heart thumping hard...just like a cave man needs fight or flight to run away from a lion...but gee how funny fight or flight and here I am flying" and then "stop that this isn't the time to be thinking about science stay on task!" So I guess I was sort of laughing a bit inside at that.   I wasn't at all panicked but I was very very full of adrenaline, which is not the same thing.  Most of all I just saw myself landing on the runway anyway and I was mad and I figured dang it lets get this done.  Having practiced these maneuvers many times really helps with visualizing what needs to happen.

Edited May 3, 2018 by aviatoreb

[aviatoreb]

6 hours ago, jlunseth said:

Ron, another simple pre-flight test that Bruce Jaeger taught me is to run your finger around the inside of the exhaust to see if the grit is dry or grimy.  Grimy/oily may be an oil leak in the turbo.  I don't do it every pre-flight just because it means having to wash my hands afterwards to get the grit off, but I do it every few pre-flights.  Obviously, this is not something to do if the pipe is hot.

Huh!  I love this thread - so much collective wisdom!  Community wisdom.  Together we are smarter.  I never thought of this one!  Thanks!

[aviatoreb]

4 hours ago, Bennett said:

Ive been quiet about Erik’s turbo failure as we hsve been talking privately since the date of tge incident. He did a great job, and i csn enphatize with him as i had a similar situation some years ago starting at FL 210 over mountains in winter, and like Erik, i declared an emergny, and made a power off landing at an airport. I, too, used the commercial spiral tk descend rapidly, as i was concerned about a potential fire. I assumed it was was a turbo failure, but ultimately that proved incorrect as i had failures of both the engine driven fuel pump  and the dual electric back-up pump. Amazingly there was no panic here - just fly the airplane, and since I knew I could spiral down over an airport, I spent my time on concentrating on the commercial spiral, rather than trying a restart.  

In another situation near the same area, I had the straight mineral oil (newly bebuilt engine in breakin) freeze and watched the oil pressure drop to the point to where I put the engine to idle and headed down from the flight levels to a nearby airport. This time at about 8000’ the oil pressure started back up, and I increased power to the point where I could make a normal landing.

in another instance I had to dead stick  a Piper Dakota into an airport.

Bennett you have had 3 in flight engine failures?  I misunderstood since in our discussions I was counting 2.  Yikes!  Well you win the crusty sea salty old pilot award.

[aviatoreb]

2 hours ago, peevee said:

Yes and no.

 

In our case the turbo ingested something after overhaul. The problem manifested itself about 8 or 10 hours later when the main bearing failed and it plastered the plane with oil and smoke when I went to get fuel for a trip the next day. There was no noise or indication anything was wrong. Had that happened in flight it would have probably lost the crankcase worth of oil pretty quickly with no indication until you started to see a drop in oil pressure. End result could be the same if the engine seized before you found an airport.

 

I had flown the airplane to 17,5 the day before and there was no problem maintaining power and no oil in or dripping from the exhaust before I went for fuel. I always check for a failed check valve and the security of the vband clamps in preflight 

 

We overhauled our turbos at about 1700 hours and main turbo thought they were pretty long in the tooth. It's not just the bearings you have to worry about, the turbine blades get gunked up and blasted and eroded by exhaust gasses too.

How do you check the check valve before every flight?

I just replaced a check valve (during the fix from Monday's incident) (preemptively) and the other I had checked - but the check seems to involve partial disassembly and applying pressure against the system with injectors out.  What can you do before every flight?

Plus which check valve?  My system has two check valves - one into the turbo and one out.  The in is simply there because the turbo sits on the bottom of the case, to prevent oil from the case from gravity flowing back into the turbo as it sits.

[peevee]

2 hours ago, kmyfm20s said:

I’m assuming it is a common TIT probe for both turbos? It would be nice if there was something that could have indicated one was offline.

There is, but that's reading the exhaust temp and since the turbos wye together into the intake no disparity was noted between left and right the engine ran basically normally, aside from the massive amounts of metal coursing through its veins. It's not like the mixture went way rich dropping the tit.

[Bennett]

39 minutes ago, aviatoreb said:

Bennett you have had 3 in flight engine failures?  I misunderstood since in our discussions I was counting 2.  Yikes!  Well you win the crusty sea salty old pilot award.

Not to mention a throttle coming off in my hand at takeoff - fortunately a long runway allowed me  to land - used every bit of it, and autopilot runaway trim (down) twice, plus a jammed up trim (mechanic left flashlight in tailcone). Over the decades of Flying I have had my share of stuff breaking, but thanks to practice and thinking ahead about “what if’s” saved the day. Very similar to the “what if’s” we practice, think about, and equip our boats for ocean racing. 

[peevee]

48 minutes ago, aviatoreb said:

How do you check the check valve before every flight?

I just replaced a check valve (during the fix from Monday's incident) (preemptively) and the other I had checked - but the check seems to involve partial disassembly and applying pressure against the system with injectors out.  What can you do before every flight?

Plus which check valve?  My system has two check valves - one into the turbo and one out.  The in is simply there because the turbo sits on the bottom of the case, to prevent oil from the case from gravity flowing back into the turbo as it sits.

Sign of a failing check valve is as noted by another poster, oily residue inside the exhaust and a potential small drip or a large drip if it completely lets go. Run your finger around in there. Our rocket ran pretty clean with a light gray soot and it was easy to tell. The exhaust is so short on the rocket I'd expect to see an increase in greasy residue on the belly also.

There are two on most. From the oil galley down into the turbo and from the turbo up to the scavenge pump. I suspect the bottom one would be the more problematic of the two ad it would backflow from the scavenge pump. If the bottom goes oil will fill the turbo and work its way where it shouldn't and out the exhaust eventually. Otherwise you might just see some smoke on start up. 

 

You can remove them, put a rubber hose on the outlet and fill with solvent and let it sit to see if it leaks. Also on the tat setup they have to be orentated correctly with the hinge at the top.

Edited May 4, 2018 by peevee

[DanM20C]

59 minutes ago, aviatoreb said:

Huh!  I love this thread - so much collective wisdom!  Community wisdom.  Together we are smarter.  I never thought of this one!  Thanks!

I was going to ask you if you did this. 

I’m curious if turbos generally fail slowly or if it’s common to fail quickly without warning.

I examine the turbo closely during pre flight, I always run my finger in and look at the exhaust. If I ever find any signs of oil in the exhaust during preflight I’m staying on the ground. 

Cheers,

Dan

[peevee]

4 minutes ago, DanM20C said:

I was going to ask you if you did this. 

I’m curious if turbos generally fail slowly or if it’s common to fail quickly without warning.

I examine the turbo closely during pre flight, I always run my finger in and look at the exhaust. If I ever find any signs of oil in the exhaust during preflight I’m staying on the ground. 

Cheers,

Dan

You could call Gary main at main turbo and he'd be happy to talk your ear off.

 

My limited undetanding is that the main bearing is steel and usually doesn't wear out or leak unless something happens like the turbine housing makes contact with the turbine wheel or crud built up under it or something else unbalances the turbo causing it to wobble and wear against the bearing. That's kind of how Gary explained it or what I remember of it.

 

The turbine side take a lot more wear than I expected compared to a car. Gary seemed to think it was a side effect of the mixture not being perfect like a car being managed by the ecu (my words not his and again my crappy memory)

Edited May 4, 2018 by peevee

[aviatoreb]

22 minutes ago, DanM20C said:

I was going to ask you if you did this. 

I’m curious if turbos generally fail slowly or if it’s common to fail quickly without warning.

I examine the turbo closely during pre flight, I always run my finger in and look at the exhaust. If I ever find any signs of oil in the exhaust during preflight I’m staying on the ground. 

Cheers,

Dan

I did not do that test - I only learned about here, today.  I sure will in the future.

I can say that my belly is clean, as I was crawling down there on Tuesday trying to figure out if the oil was dumped, but all I saw was a clean shiny belly.

[aviatoreb]

41 minutes ago, peevee said:

Sign of a failing check valve is as noted by another poster, oily residue inside the exhaust and a potential small drip or a large drip if it completely lets go. Run your finger around in there.

I see - I didn't realize that he was describing a test for the check valve that way.

They directly checked the check valves by applying hoses and pressure and so forth, yesterday.

[peevee]

32 minutes ago, aviatoreb said:

I did not do that test - I only learned about here, today.  I sure will in the future.

I can say that my belly is clean, as I was crawling down there on Tuesday trying to figure out if the oil was dumped, but all I saw was a clean shiny belly.

That surprises me. The short exhaust on the rocket meant a perpetual sooty belly on ours.

[Hank]

8 hours ago, jlunseth said:

Ron, another simple pre-flight test that Bruce Jaeger taught me is to run your finger around the inside of the exhaust to see if the grit is dry or grimy.  Grimy/oily may be an oil leak in the turbo.  I don't do it every pre-flight just because it means having to wash my hands afterwards to get the grit off, but I do it every few pre-flights.  Obviously, this is not something to do if the pipe is hot.

Even when I land after a long XC and taxi to the fuel pump, by the time i shut down, get out and grab the ground cable, my exhaust is cool to the touch. Are your turbo exhausts really that much different? 

[jlunseth]

Probably not, I don’t know,  I just have never tried that right after landing and didn’t want someone else to think, well he does it, so me too. 

[peevee]

13 minutes ago, Hank said:

Even when I land after a long XC and taxi to the fuel pump, by the time i shut down, get out and grab the ground cable, my exhaust is cool to the touch. Are your turbo exhausts really that much different? 

Mine will still but the shit out of me.

Our tit runs 1500-1650 depending how lean you run it. NA I never paid attention to the actual number just the peak so I honestly don't know how hot it runs. I assume close to that?

[Hank]

3 minutes ago, peevee said:

Mine will still but the shit out of me.

Our tit runs 1500-1650 depending how lean you run it. NA I never paid attention to the actual number just the peak so I honestly don't know how hot it runs. I assume close to that?

I usually run 1450-1500°F, and it's cool to the touch amazingly fast. It's where I clip the ground wire at the fuel pump after landing.

[DanM20C]

2 hours ago, peevee said:

You could call Gary main at main turbo and he'd be happy to talk your ear off.

I’ve talked with Gary several times since buying my 231 back in August.  One of these days I should buy something from him.  When the time comes my turbo WILL be overhauled by Main!

 

2 hours ago, peevee said:

My limited undetanding is that the main bearing is steel and usually doesn't wear out or leak unless something happens like the turbine housing makes contact with the turbine wheel or crud built up under it or something else unbalances the turbo causing it to wobble and wear against the bearing. That's kind of how Gary explained it or what I remember of it

That makes sense.  I wonder how effective the finger in the exhaust trick is to preventing failures like @aviatoreb.  I’m going to continue to watch the inside of the exhaust pipe like a hawk.  Hoping that I can catch this sort of failure early.  My turbo looks great on both sides with 750hrs.  Keeping fingers crossed.  I inspect everything at oil changes also, like @Marcopolo

Cheers,

Dan

[peevee]

Main overhauled our turbos for 5 amu and then again 2 weeks later for 2.7amu and then the wastegates for an unknown amu, I think 2ish. I've spent enough for both of us.

 

I didn't read Erik's issue closely, it sounded like the bearing slop so I doubt it gave much warning just a gradual wobble. Like I said Gary said that oil seal is a steel sleeve and doesn't just leak like people think.

 

Throw some mouse milk on your waste gate too, they can get sticky.

Edited May 4, 2018 by peevee

[peevee]

8 minutes ago, Hank said:

I usually run 1450-1500°F, and it's cool to the touch amazingly fast. It's where I clip the ground wire at the fuel pump after landing.

Yeah me too and I slipped somehow  and burned myself bad enough to blister. And that's after a lengthy low power setting descent.

[aviatoreb]

11 minutes ago, DanM20C said:

I’ve talked with Gary several times since buying my 231 back in August.  One of these days I should buy something from him.  When the time comes my turbo WILL be overhauled by Main!

 

That makes sense.  I wonder how effective the finger in the exhaust trick is to preventing failures like @aviatoreb.  I’m going to continue to watch the inside of the exhaust pipe like a hawk.  Hoping that I can catch this sort of failure easy.  My turbo looks great on both sides with 750hrs.  Keeping fingers crossed.  I inspect everything at oil changes also, like @Marcopolo

Cheers,

Dan

I just bought my overhaul exchange from Main.

Funny - I have been doing my "check exhaust stack" on my check list dutifully for years, but I was checking for stability and cracks apparently completely misunderstanding the point, I am embarrassed to say.  Well - live and learn - thank goodness.

I want to make the list of wonderful suggestions into a numbered list but its scattered about here - where is Anthony?  I want the summary in Anthony-style.

[DanM20C]

1 minute ago, aviatoreb said:

Funny - I have been doing my "check exhaust stack" on my check list dutifully for years, but I was checking for stability and cracks apparently completely misunderstanding the point, I am embarrassed to say.  Well - live and learn - thank goodness

You didn’t misunderstand the point. Checking those v-bands and looking for cracks is very important. You were checking for a different failure mode, one that the airline FO would have seen a trail of smoke!  

Cheers, 

Dan

[aviatoreb]

24 minutes ago, DanM20C said:

You didn’t misunderstand the point. Checking those v-bands and looking for cracks is very important. You were checking for a different failure mode, one that the airline FO would have seen a trail of smoke!  

Cheers, 

Dan

:-). Phew so I am not a COMPLETE dummy - just a partial dummy.

Edited May 4, 2018 by aviatoreb

[DanM20C]

10 minutes ago, aviatoreb said:

:-). Few so I am not a COMPLETE dummy - just a partial dummy.

Dead stick from 16.5K without a scratch? You are in no part a Dummy!