New cylinders

flyer170 · Post by **flyer170** » Mon Sep 30, 2002 3:46 pm

Regarding my cylinders here is the latest. In 183 hours I have had to replace 3 cylinders 1, 3, 5.
1 and 3 failed in flight when the rocker arm bosses broke, number 5 was replaced when a crack was found during annual.
I have replace all three with new steel TCM cylinders.
Checking back through the engine logs to 1950 these are the first new cylinders. That means to me that 2,4, and 6 are very suspect. Some cylinders were replaced with "servicable or reconditioned" cylinders.
This is the original engine (C-145) from the factory. 4,000 hrs on the aircraft.
I think I had better replace the other 3 cylinders before I take any more long trips.
What do you think

Bob

Post by **GAHorn** » Mon Sep 30, 2002 5:23 pm

Accurate record-keeping is an absolute must for maintenance records. If you are confident that the cylinders that are presently installed are "reconditioned"/"used"/"serviceable" replacements of unknown or undocumented origin, ...then I would agree that they are suspect.
When used/reconditioned/serviceable cylinders are purchased, even if purchased from reputable suppliers, it is rare that the actual number of hours/cycles they've been through is documented. You can only bend a paperclip so many times before it breaks.
Therefore, I believe that when cylinders are replaced on an engine that only cylinders of new manufacture should be used on fresh overhauls, unless the cylinders to be re-installed are 1) your own 2) you know how many times they've been reconditioned/chromed/etc.
Using a new cylinder all the way to TBO, then reconditioning it (including boring out to oversize) and running it again, then reconditioning it again with an approved chrome-plating for one more TBO run, is about all I am comfortable with. I personally believe the cylinder should then be destroyed.
I would only install a cylinder selected from overhaulers (without complete previous service documentation) on a mid-life or higher time engine, and only then for the purpose of completing that engine run. It should then be destroyed. My 2 cents.

flyer170 · Post by **flyer170** » Tue Oct 01, 2002 1:22 pm

George..... I have noticed that the new cylinders have a design change and the area of the rocker arm bosses has been increased. Stronger I suppose.
There is an AD about this problem but just checking for cracks may not be the answer as they just might fail without cracking that can be seen in time. I did follow the AD and inspected for cracks, 183 hrs later another boss broke.
Even if an older cylinder has been chromed and reconditioned etc. the rocker arm boss design on the older cylinders should still be suspect. I'm agreeing with you.
The owners of engine overhaul businesses see many more of these types of failures than we realize.
Bob