Lycoming Cylinder Ring Chatter

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ddn

Filing Flight Plan
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Jan 13, 2023
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David Dellanave
I've got an O-235-L2C(M) that has recently come back from inactivity. This chatter type wear pattern was present before running it for 25 hours and getting pretty high aluminum, chromium, and iron (and nickel) in the oil analysis. Compression was 73/80. I guess it's probably safe to say it's going to need a new cylinder, but I'm wondering if anyone has seen this before and what the cause could be? I am away from the logs at the moment but I believe it's a Superior cylinder with under 100 hours on it. Will be scoping it and checking compression again, but looking for experienced input in the mean time.

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I’ve seen it on a fish spotting 172.

At the time the thought was extended low power ops may be involved.

Never knew for sure though.
 
When there is more pressure in the crank case and less in the cylinder as the piston is moving up.

I would have expected it on other cylinders too. Perhaps there is a difference in that one cylinder, piston, and ring set.

As always, opinion, not an A&P.
 
Flight school airplane, so maybe improper break-in when that one cylinder was replaced?
 
You may be able to have the cylinder overhauled (bored and new piston and rings). These days, a LOT shorter time then getting a new cylinder.
 
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Pinecone said:
You may be able to have the cylinder overhauled (bored and new piston and rings). These days, a LOT shorter time then getting a new cylinder.
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They don't bore them. They hone them to a small oversize.

That cylinder might have been a poor job of initial boring when it was made, and the honing to final size didn't clear up all the boring machine marks. Unlikely, but one has to wonder. It looks pretty severe. The presence of aluminum in the oil sample suggests that the piston lands are suffering from it, so flutter is more likely.
 
ddn said:
I'm wondering if anyone has seen this before and what the cause could be?
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Seen it in round engines but not a common discrepancy in any properly operated engine. My 1st guess is not broke in properly. Or there was a physical issue with the cylinder specs/parts. Considering you ran it with that existing condition may want to just pull it and send out for OH. Hopefully it is still repairable and the piston still serviceable. And as a side note have only heard the "flutter" term used vs chatter.
 
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