Effects of little use on engines


Well-Known Member
I was looking at a 1978 Decathlon 8KCAB with only 828 hours on it since new. The engine has never been overhauled obviously (it has an AEIO-320-E2B) and since December of 2001 it has only run for 30 hours. The plane has been stored in Florida since 1989.

My question is what kind of condition would the engine be in after this little use in such a long period of time?

The compressions in the cylinders are all in the low 70's except one was at 69.

I know there are some aircraft owners on the board and was wondering if any of you had issues with engines that ran infrequently like this.
Aside from directly pouring sand into the engine, or taking a sledge hammer to the valve guides or what not - letting an engine sit without running it is about the single most harmful thing you can do to it.

What happens is water from condensation (warming up/cooling down) develops on the internal parts and then rust forms. An engine that has sat for an extended period of time is bad mojo. And in this case you need to worry about corrosion from salt water (FL is notorious for this problem) not only in the engine but the airframe.

However, if it has been "pickled" (oil drained and a special concotion of fluids added) for long term storage you should be good.

But those compression numbers may be starting to get on the low side. What did the mechanic say when he ran the check? If those are the numbers supplied to you by the owner it would really be worth the cash to get an in-depth inspection done on the engine (and airframe) by your own mechanic.

The upside is if you have the cash - and your inspection confirms the engine is more worn than should be - work the guy down on the price, buy the aircraft and dump a new engine into it. That way you know exactly what you're getting.

Another upside is while 30 hours in a little under two years isn't great it's not exactly horrible either. An engine that has sat without being turned over once in three or four years I'd be a little more worried about.

Get and A&P and dig into it.
this airplane most likley has the IO-360 lycoming in it, this engine is a 2000 TBO. If it has an AIO-360 then **I think** the TBO is 1500hrs. either way Lyc reccoments no more that 12 years TBO even if the hours were under 2000.

If you want to buy it then what I would do is take it for a good one hours flight, pull an oil sample and send it ff to Aviation Labs for a test (send the filter too) cost about 50$ for both oil and filter analysys.

I sample ever 25 hours, 50$ for piece of mind you bet.

Then it becomes a gamble Just because the Oil is good, doesn;t mean that something isn't worn, and you may end up pulling the engine either way. I would have in my pocket 5-7000.00 as a safty net assuming I would need to overhaul before we planned on it.

Our aiplane sat for 3 years with about 10 hrs a year, when we purchased it, we pulled the engine after 6 months.

The up side is you can use that ( storage low flight itme) to your advantage. I would offer a price that assumes the engine is nothing more than a paperweight and see where that goes.
The compression numbers are from the last annual (Dec 02). All the cylinders showed a drop in their compression readings since the preceednig annual except for the #1 which showed a 1 point increase.

To the best of my knowledge the engine was never pickled and it has been stored in Florida (and run intermittanly) since 89. The plane just hasn't run a lot since the owner didn't fly it that often.

A study of the logs showed nothing unusual but that engine running about 30 hours in the past 3 years bothered me.

When is a compression too low that opening the engine becomes a necessity?

Thanks for the reply pilot602.
The compressions on an a engine that has not flown are meaningless.

good numbers on an active airplane are above 70, ours all run 77 or above with 500 hrs on the new engine.

ok numbers are in the 60s

under 50 look for a new cyl.

It's the AEIO-320-E2B, and you're right the TBO is 1600hrs. Also thanks for the info on Lycoming recommending an overhaul every 12 years, I wasn't aware of that either.
I sample ever 25 hours, 50$ for piece of mind you bet.

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Wow! How many hours are put on the plane in a year? (Nothing wrong with peace of mind.)