Bodhi, A&P questions for ya

[Wolfala]

Hey guys,


Here's the scoop. On about Jan 28 I did an oil change for the 50 hour, and then a renter took the plane 2 days later on a short 1 hour hop. The day after that I downloaded the data from the Engine Monitor before conducting training that evening and looked at the data when I got home.

What I saw sent me through the ****ing roof. This is a

http://www.cirruspilots.org/uploaded_images/3-308858-Graph.pdf
http://www.cirruspilots.org/uploaded_images/3-308983-Flt104.pdf

The guy was no higher then 1500 feet the entire time, CHT's around 450 and 110% of their redline, and the engine at 107% of its maximum rated horsepower. The guy basically kept it at takeoff power for 5 minutes and never powered back for a cruise climb - and when he did it was still at 95% power. Then, towards the end - he shock cooled it at 200* per minute and shock heated it back at 200* per minute.

So yesterday, per Continentals instructions we did an overheat inspection.

Compressions were the first thing and I put the results from December's Compression and yesterdays side by side.

Dec, 2, 2007   Feb-9, 2008
   
#1 68/80   #1 75/80
#2 75/80   #2 70/80
#3 76/80   #3 48/80
#4 77/80   #4 70/80
#5 71/80   #5 77/80
#6 71/80   #6 79/80

Here's the bad news. #3 Jug was 40/80, leaking past the exhaust valve and the rings and the #2 Jug was 70 with leaking past the rings.

While draining the oil which had about 8 hours on it, I took a sample and will send it off to Blackstone Labs for analysis. These were the most recent oil analysis.

http://www.cirruspilots.org/uploaded_images/3-310236-D29446.pdf

I guess my question is, and i'm only showing you data from 1 leg of his flight - there was a return leg with a similar temperature profile - what damage can be internal as a result of this guy? I know for a fact he took some life off the engine - its just a question of how much and in what areas.

Things like Bearings will be masked by lead blowby, obviously the rings will show up in the oil and through the compression check. Its gonna go out to insurance and the guy will get nailed, but the question is - apart from the things we can observe like the compressions and ring damage, what else is there that might warrant a tear down?

Wolf

[FrodeMk3]

I know this was really meant for Bodhi, Wolfala, but I was just wondering-Would the insurance only pay for a rebuild of your existing motor, or will they buy you a complete, new unit from Continental?

And, wouldn't most of the overheating damage be limited to the cylinders, cylinder heads,valves, and possibly the pistons? I would think your Crank, Rods, and the main case would be ok.

[Wolfala]

That remains to be seen. I think the deciding factor would be how the oil analysis turns out. If it shows up at 10 hours looking like it has been run for 50 - then there would be a case for that. But the thing which gets me is just having no way to know about internal damage - i.e. the bottom end of the crankcase.

[culero]

Originally posted by FrodeMk3
I know this was really meant for Bodhi, Wolfala, but I was just wondering-Would the insurance only pay for a rebuild of your existing motor, or will they buy you a complete, new unit from Continental?

And, wouldn't most of the overheating damage be limited to the cylinders, cylinder heads,valves, and possibly the pistons? I would think your Crank, Rods, and the main case would be ok.

Insurance companies pay what they believe is the minimum cost to reimburse you for your actual damages. To justify a replacement, you have to show that the repair cost approaches the replacement cost.

Overheating can also impact lubricated rotating parts since overheated oil doesn't perform as it should.

[Golfer]

Nevermind Wolf already has!

Good luck, Alex.

[Casca]

I'm not going to tell you its no big deal, I would be fit to be tied if it were my ship.

Very impressive engine monitoring system by the way.

What I'm seeing, if I'm reading this correctly, is a three minute excursion above CHT redline starting at 21:08:38 and lasting till 21:11:38 with the worst case briefly about 111% of redline.  The interesting thing here is that the largest excursion seems to be cylinder 5 which is not the one manifesting the problem.  While this is not desirable I wouldn't anticipate any problems in the bottom end.  The thing I would be more concerned about is the shock cooling profile.  Damage you could reasonably expect from this would include cracked heads.  When the engine is cooled rapidly from the outside-in stresses are introduced as the result of the metal trying to contract on the outside when its staying big on the inside.

I don't have any experience with an IO-360-ES although some of the Continental IO-360 series have a reputation for being a little high strung (the TSIO-360-GB on the Mooney 231 for instance).  That being said I have run many IO-520-Ds right at CHT redline for day after day weeks at a time and they seem to be highly reliable.

On the exhaust valve it is frequently possible (and I'm not making anything that could be construed as a mechanical recommendation here) to grind it in situ.  It would be nice to be able to see it to check for seat recession if you know someone with a borescope.  Also can check the bores for any spalling.

On the blow by.  If rings get hot enough long enough they can get soft.  This could be showing up on a static compression test.  I always regard static compression tests with suspicion.  They can tell you a lot but have some limitations.

Most aircraft have some variation of Dykes ring, either wedge or L shaped. The combustion is actually helping the ring to seal.  What I usually do to check for blow by is to modify an oil cap by epoxying a tube or B fitting into it that I can connect to a manometer or airspeed indicator then go fly it.  You probably need to look up the numbers but you don't want more than 2 or 3 inches of water crankcase pressure.  This should be, I think, about 90 or 100 mph indicated on an airpeed indicator.  Lycoming used to have a chart that converted mph airspeed to inches of water.

Run the compression test again after you fly it.  You have probably done this enough so you are aware that by rocking the prop you can sometimes hear the rings pop in which will bring the compression value up.

Best of luck.

[Wolfala]

Apart from the CHT issue was the power output. One the flight you are being shown (there was a return leg), he was sitting at greater then 85% power continuously - which Continental and the POH and the rules we put in place at the club strictly forbid. You can think of 13 GPH as 85%. The only setting 13 GPH would be used at is a cruise climb - which above 6K you couldn't produce more then 83% anyway.

But he was on the deck - no higher then 1500 feet. And at least 85% from 21:07 to 21:30, not including the shock profile and return leg which is in another file. So basically the guy went balls to the wall thinking **** was fine - paid no attention to the temps or continuous power limits for his altitude - and here we are.

The compression tests were run cold first, and then rechecked when the engine was hot before we drained the oil out and replaced it with a new batch. The compressions were identical - same leaks on #3 and #4.

I'm confused on 1 part - you want to measure the internal crankcase pressure with modded oil cap? Would that work by rotating the prop through to TDC and looking for the change on the ASI? Never seen or heard that approach.

As an aside, there was another instructor and owner next to me while all of this was going on. The other owner had an EI instrument but without data recording. I think the results of the day were enough to horrify him into getting a data module added to his existing setup. This whole thing was really a sickening experience.

This was our guidence from TCM
http://www.tcmlink.com/pdf2/SB03-3.pdf

[Bodhi]

Wolfala,
I don't overhaul engines.  We do airframes, systems, and maintenance (change cylinders and accessories) but we never overhaul the engines.  Just way to specialized for us.

That said, if this guy obviously ran the CHT's that high, I would be interested to see what else he did to the aircraft.  (IE. G's and aerobatics) From the info that I see, it is a good guess that cylinder #3 is more than likely toast.  As Casca mentioned, it is possible that the rings just aren't seating, but like he said, rock the prop and they should seat.  Or again as Casca said, go fly it for 45 minutes, and do the cylinder pressure checks again

If it was me, I'd get that latest sample off to Blackstone.  They are going to be able to obviously see a spike in metal deposits in the oil, and more than likely will have some questions regarding the usage.  It may be best to add some notes with the oil informing them of the situation.

Sorry I can not be of more help, but good luck, and nail this guy down.

[Wolfala]

I wrote a 2 page note to Jim Stark at Blackstone and attached the 17 pages or so of data on how the engine was run by that guy. But are there anythings that I should have Jim pay particular attention to?

[RTR]

Well, as a start you are probably looking at having to replace the exhaust valves and possibly guides as well. Seeing compression as low as 48 is a pretty good sign there.

The valves "may be" salvageable, however in my experience (and have just gone through a simlar scenario on a TCM engine) the valve (s) are going to be burnt fairly signifcantly.

what's the TSO of the engine? Has it had a top O/H or cylinder work done recently?

As far as the bottom end goes, it is possible that the bearings were heat damaged, but the only real way to see is by splitting the case, which will lead to significant $$.

At the very least I suspect you have some work ahead of you. I would want to look at each valve and guide for sure.

cheers,
RTR

[Casca]

Originally posted by Wolfala

I'm confused on 1 part - you want to measure the internal crankcase pressure with modded oil cap? Would that work by rotating the prop through to TDC and looking for the change on the ASI? Never seen or heard that approach.
This was our guidence from TCM
http://www.tcmlink.com/pdf2/SB03-3.pdf

This is a test to check for blow by.  Mod a spare oil cap by epoxying a tube in it.  Install it on the airplane and slide or clamp a tube to it.  The clear plastic tubing you can find at Ace Hardware works fine.  Run the tube to the cockpit and plug the other end of the tube into an airspeed indicator.  You can use a manometer if you have one but I have always used an airspeed indicator.  When you go fly the aiplane the crankcase pressure will register as an airspeed on the ASI.  This is a way to look at any blowby issues under operating conditions.  Going from memory here but I think the maximum value you want to see is between two and three inches of water.  This corresponds to between 90 and 100 mph indicated on the ASI.  As I mentioned Lycoming used to have a chart that converted indicated MPH to inches of water.  It was in the form of a Service Bulletin and I can't lay my hands on it.

This test has been around for a million years and you don't hear much about it any more but it is a good way to figure out if you have a blowby issue.

[Bodhi]

Originally posted by Casca
This is a test to check for blow by.  Mod a spare oil cap by epoxying a tube in it.  Install it on the airplane and slide or clamp a tube to it.  The clear plastic tubing you can find at Ace Hardware works fine.  Run the tube to the cockpit and plug the other end of the tube into an airspeed indicator.  You can use a manometer if you have one but I have always used an airspeed indicator.  When you go fly the aiplane the crankcase pressure will register as an airspeed on the ASI.  This is a way to look at any blowby issues under operating conditions.  Going from memory here but I think the maximum value you want to see is between two and three inches of water.  This corresponds to between 90 and 100 mph indicated on the ASI.  As I mentioned Lycoming used to have a chart that converted indicated MPH to inches of water.  It was in the form of a Service Bulletin and I can't lay my hands on it.

This test has been around for a million years and you don't hear much about it any more but it is a good way to figure out if you have a blowby issue.

Casca, I know of this, and was also warned to never do it as a certificate holder, as they can yank it and fine the crapola out of you should anything go wrong.

Better to just use a spare breathing port.

[Casca]

Bodhi:

That could certainly be a consideration depending on who is doing it and where it is being done so I want to get a disclaimer out front: disclaimer/"I'm not telling anybody to do anything." /end disclaimer.

That being said this procedure is a bona fide Lycoming Service Letter (one's mileage with Continental may vary) and my Principal Maintenance Inspector out of the KC FSDO wouldn't have any heartburn with it.

[FrodeMk3]

Originally posted by Bodhi
Wolfala,
I don't overhaul engines.  We do airframes, systems, and maintenance (change cylinders and accessories) but we never overhaul the engines.  Just way to specialized for us.

That said, if this guy obviously ran the CHT's that high, I would be interested to see what else he did to the aircraft.  (IE. G's and aerobatics) From the info that I see, it is a good guess that cylinder #3 is more than likely toast.  As Casca mentioned, it is possible that the rings just aren't seating, but like he said, rock the prop and they should seat.  Or again as Casca said, go fly it for 45 minutes, and do the cylinder pressure checks again

If it was me, I'd get that latest sample off to Blackstone.  They are going to be able to obviously see a spike in metal deposits in the oil, and more than likely will have some questions regarding the usage.  It may be best to add some notes with the oil informing them of the situation.

Sorry I can not be of more help, but good luck, and nail this guy down.

Bodhi, you made me wonder about something...If the renter never got above 1500 ft., Which would have been somewhat unsafe for acrobatics, to say the least, I was wondering what else he could have been doing? On just a 1 hour flight?

Wolfala, could a lot of landing/takeoff's do this? Wouldn't that keep your CHT over 85% if he was doing touch-n-go's?

That said, maybe cast an eye at the airframe, and the landing gear and wheel brakes, too.

[Wolfala]

In short, no.

If you look at the complete report at:

http://www.cirruspilots.org/uploaded_images/3-310466-Datamod.pdf

The graph depicts a steady plateau. Only a reduction in power toward the end with the cliff on the EGT and CHT would say he was landing. But on the pure data portion of the report, Fuel Flow (FF) is steady in the 13 range from 21:07 onward. Landing would be in the 3 to 5 range.

The 85% figure is a function of fuel flow. So 13 GPH is 85% power for that engine. Cylinder Head Temperature is dependent on the power output, deck angle and the cooling in the engine cowling.

The gear was inspected yesterday - and while I found a broken bracket for a wheel pant - I believe that is more metal fatigue then this 1 incident.