I know there have been a lot of threads on time since overhaul, but this is specific to the C90 as I have limited experience with this.

I'm looking at two planes, both with C90s. One is mid time, around 900 hours. I'll see the logs soon, but I think it may be a good 15 - 20 years since overhaul.

- Is this a concern if the plane was flown regularly during that time, or does age eventually play its part?

- If I do a thorough annual/prebuy, will the mechanic catch most age related issues, or can many things still pop up unexpectedly?

The other engine recently had a top so I'm not so worried about that one.

Thanks!

Got 11 years and 886hr out of an overhaul done in 1980 and parked until 2001 with 108hr on the "field overhauled" O470R! My partner flew it very hard at first then backed off...i got into plane in 2011 and 55hr later mucho pitting in cylinders and time for at least a top overhaul...we decided to PPONK our 182 with a built engine...i think the mechanic put marvel in the cyls and just ran it hard, but i live in dry hot central valley CA...not much rust or condensation to worry about here.

I know a total of 994hr doesnt sound too good but the thing sat for 21 years absolutely untouched other than a guy coming in and turning the prop over 50 times very 2 years.


Mike

Time can be a factor if corrosive processes are in play. Regular use is essential for minimizing or eliminating this sort of damage. Other than that calendar time will only be a factor in components such as rubber hoses, seals and gaskets. On a C90 that would be intake and fuel hoses, pushrod housing and crank seals, magneto, accessory housing, oilpan and carb gaskets.

To my metallurgically untrained mind 900 hours in 15 years is not being flown regularly. That is an average of 5 hours a month which is ok but in reality it likely means 10 hours a month during flying season and 6 months of nothing. Over 20 years it is even worse.

I had a bad experience with an engine that sat not pickled for 5 years. It has .6 hr. on a Lycoming prop strike tear down inspection. It looked good, bore scope, compressions were all good. At 900 hr it started making metal, directly related to sitting not pickled.

Personally I will never buy anything with an engine that has sat a long time, UNLESS, it is priced where if I have to overhaul it I will come out ok price wise.

G'Day

Thanks guys! These engines weren't pickled, but they were run 20-50 hours every year. My question really has to do with age in general.

OEMs I think recommend 1800-2000 operating hours or ~12 years for an overhaul, but no one ever mentions the 12 year portion. Great, you only have 1200 hours on the engine, but it hasn't been overhauled for 20-30 years. Even with regular running, do things just "get old" in the engine, like seals, etc.?

I've got a Continental 60-100 hp operators /parts/ overhaul book online -send me a email direct [email protected] and I'll get you what I have.

As I said, gaskets and seals would be the main concern in regards to calendar time but lengthy periods of non-use need to be considered as well. It depends on the situation and I can cite two examples that I was involved in. One was a Lycoming O-320 on a Citabria that had sat for about 9 years. The first thing I noticed was that the impulse coupler was not working so I pulled the right mag and the drive gear was completely encrusted with a thick coating of rust. In this case the engine had been destroyed internally by idle time. The second case was a 182 with a Continental O-470 that had sat un-used for 12 years, we changed the oil and fired it up. The new owner has put over 600 hours on it with no problems.

Both aircraft were in hangars in central valley California area, they were about 5 miles from each other. The Citabria was on a farm with a private strip, the Cessna was at an airport which is known for it's nearly constant windy conditions. Neither of them had been pickled or preserved in any way.

So it's a crap shoot but I determined from those experiences that the elements gain access to the internal engine parts mainly through the crankcase breather so pulling a mag and looking at the inside of the accessory case can be revealing.