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Cracked Cylinder

Hello,

I have a G36 with the TAT Whirlwind III STC. Currently I am doing the annual inspection and, as part of it, the engine was borescoped yesterday, finding some cracks in cylinder 6 (please see attached pictures). The airplane is located in Chile, where borescopes are a new thing, thus this is the first time that I have inside pictures of the cylinders. I would like to ask about which options I have, other than replace the entire cylinder, and how bad the crack is (I don’t have any experience with boroscopes and cracked cylinders)
The engine has around 1370 hours SN and around 400 from top overhaul with millenium cilinders. All the others cylinders looked Good and compressions are ok.

Thanks in advance,

Francisco

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You really have no choice but to replace the cylinder. When they do a compression check is air escaping around the spark plug hole on the exterior of the cylinder?
You might want to call Superior and see if they will provide any amount of warranty on a new cylinder.

Bob Ripley
ABS Technical Advisor

Posted 10/17/2023 - 4 months ago
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I would need to rule out a casting or carbon deposit irregularity before replacing the cylinder. While the scope is positioned as the last few photos, reach in through the spark plug hole with a long artist brush with a bend in it, brush end saturated with a light oil, and pass it over the mark at 90°; if the oil wicks down the line, chances are pretty good it is a crack. If there is no wicking, I'd reassemble and do a ground run to temperature and repeat that test. If you do this, please report back with the results.

Mike
ABS Technical Advisor

Posted 10/17/2023 - 4 months ago
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Unfortunately, in my opinion, cylinder replacement is your only option. I do a lot of borescopes in my work and can tell you this crack will only continue to propagate. I have attached a picture from a borescope of an IO-550-B with a similar problem but much more along in the "process of failure". We replaced this cylinder. Your crack will eventually become like this going all the way to the valve. The compression on this cylinder was zero. Best to “deal with” it now rather than wait for the ultimate failure.

Jim
ABS Technical Advisor
ABS BPPP Instructor
ABS Ambassador
CFII/MEI, A&P/I-A

Photo on 9-19-23 at 3.58 PM #3 copy.jpg - 409.1 KB

Posted 10/17/2023 - 4 months ago
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Cracked Cylinder