Pitting cylinders

[Dr. O]

Nothing makes an airplane deteriorate faster than sitting around.
It has 'likely' been sitting a long time between infrequent flights which means dry starts.
A dozen dry starts can put as much wear (or more) on the critical parts as a couple thousand hours of flying.
If cylinders on a Lycoming hangar queen are pitted, so is the cam.
And I would be suspicious that hoses and accessories are affected also.
Either negotiate the price to account for this or walk away.

 

[N801BH]

Nothing makes an airplane deteriorate faster than sitting around.
It has 'likely' been sitting a long time between infrequent flights which means dry starts.
A dozen dry starts can put as much wear (or more) on the critical parts as a couple thousand hours of flying.
If cylinders on a Lycoming hangar queen are pitted, so is the cam.
And I would be suspicious that hoses and accessories are affected also.
Either negotiate the price to account for this or walk away.

Great advice....

 

[Dan Thomas]

Nothing makes an airplane deteriorate faster than sitting around.
It has 'likely' been sitting a long time between infrequent flights which means dry starts.
A dozen dry starts can put as much wear (or more) on the critical parts as a couple thousand hours of flying.
If cylinders on a Lycoming hangar queen are pitted, so is the cam.
And I would be suspicious that hoses and accessories are affected also.
Either negotiate the price to account for this or walk away.

Cylinder pitting is very often due to ground runs or very short flights. Condensation from blowby does it. I have taken apart engines that have just been run up and found water between the pistons and cylinder walls. Ground runs are especially pointless, yet I often hear of guys doing it 'to circulate the oil," thinking they're doing the engine a favor.

 

[Tom-D]

No, it gets bolted back together. It wasn't airworthy before, it was misrepresented as airworthy.

You are wrong, many engines are airworthy, but when disassembled will not pass the service limits of the overhaul manual.

 

[Henning]

You are wrong, many engines are airworthy, but when disassembled will not pass the service limits of the overhaul manual.

I'm not having the engine disassembled, I'm paying the guy's mechanic to slip back the cylinder so I can peek at the cam, figure the bill is 2-3 hrs labor total, maybe 4 if it's a PITA cowling.

 

[Fearless Tower]

Cylinder pitting is very often due to ground runs or very short flights.

Not always. I have seen cylinder pitting begin to show up on my Baron around 950 SMOH that was not there when we borescoped on the pre-buy over 2 years ago. I have never done 'ground runs' as you describe.

 

[thomasdr72]

Anytime you disassemble to inspect something on an airplane, it's a mixed bag... Yes, on one side you can find that everything you wish to see is perfectly serviceable; on the other hand, you'll be well advised to be prepared for "surprises." IDK how many times I've taken something apart to inspect it, and found that portion airworthy--just to find one or two close-by items that were in need of attention...

Aviation is one of those places where if a guy is smart, they fix basically everything they find. It's a lot easier (and most of the time cheaper) to fix problems before they manifest into something bigger.

When I annual an airplane (even my own) I don't feel right if I don't find an entire sheet of write-ups. And in 6 years of exercising the privileges of my IA, I have yet to inspect an airplane that didn't have a full page (~25) of discrepancies (or more).

I'm spit-balling a figure here, but my personal knowledge of the lycomings I've had a hand in opening over the years, ~25% had an unairworthy cam/lifter when I pulled a cylinder. (small numbers though, YMMV) Most of those had sat around for an extended time for at least part of their service lives...

Lots of guys say it, and my personal experience reinforces it: The weak link on a Lyc is the cam/lifters. On a Connie it's the valves/heads. It's all a trade off...

"Airplanes are made to fly, sitting around makes them break" My 25-years of wrenching reinforces this to me...

Cheers!

-Dana