Major overhaul time period

simtech

simtech

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Simtech
I thought I read somewhere that a major overhaul should be accomplished after 12 years regardless of the hours. Is that right? I'm looking at a plane that was overhauled in 94 and has 700 SMOH and mid 70's on all cylinders. Not sure if being almost 20 years out means anything or not. recently it has been flown at least once a week for about a year now. This is a Lycoming 0-360.

Also, Mogas STC. Is that an airframe thing or engine thing and how would I go about seeing if it is eligible?

Thanks
 
20 years would not be a problem for me if the plane was flying regularly and in good condition.

mogas is STC by airframe. The 0360 in a Cherokee can have a mogas stc while the 0360 in the Arrow cannot.
 
simtech said:
I thought I read somewhere that a major overhaul should be accomplished after 12 years regardless of the hours. Is that right? I'm looking at a plane that was overhauled in 94 and has 700 SMOH and mid 70's on all cylinders. Not sure if being almost 20 years out means anything or not. recently it has been flown at least once a week for about a year now. This is a Lycoming 0-360.

Also, Mogas STC. Is that an airframe thing or engine thing and how would I go about seeing if it is eligible?

Thanks
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The 12 year number is a Lycoming recommendation, but most overhaul engines on condition, not hours or years.

The mogas STC depends on the airframe/engine combo. What is the aircraft? Today's problem with Mogas is that so much of it has ethanol, and you can't <legally> use that in an airplane anyway, so the STC is largely moot.
 
Overhaul it when this happens....
 

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Thanks for the replies. I'm told no fragments in the oil, no burning of oil, I think he said 1 qt every 10 hours it is using. I might go look at it this weekend. It is a 71 Beech Sundowner. I have no problem around here getting non ethanol gas, just for how long...who knows. I know for the past 1 year or so it had been flown weekly, prior to that I'm not sure.
 
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If you listen to the major engine manufactures, yes, that is there recommendations. Most do not adhere to that policy.
 
I wouldn't worry so long as the engine otherwise checks out. You really won't be able to know how often it was flown over that long a period, other than what the seller says (which might be what you want to hear more than reality). Our last set of engines we ran to 18 years.
 
Ted DuPuis said:
I wouldn't worry so long as the engine otherwise checks out. You really won't be able to know how often it was flown over that long a period, other than what the seller says (which might be what you want to hear more than reality). Our last set of engines we ran to 18 years.
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I know at least one 172P with about 1500 TT and the eninge has never been apart since new, 32 years ago.
 
timwinters said:
As a buyer you should value the plane as if it had a run-out engine, regardless of how well it's running today.
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Anyone that tells me that about my engine will get told to leave the hangar, and it hasn't flown since 1992.
 
We ran our O-470U until 1700 hrs and about 20 years before OH (the previous owner did a TOH at about 900 hours). We had to replace a couple jugs when it was at about 18 years old, at which time we were able to get a good look at most of the bottom end. Based on the extent of the normal wear (minor pitting, mostly), we decided the engine probably had another year or two of good, safe service, and planned for it's "retirement".

The main concern I'd have is with corrosion on the bottom end. Look carefully at how often the oil was changed - based on calendar time, not hours. Even with low running hours, the oil should be changed every 4 months. Maybe 6 months on the outside, a couple times during the 20 years. Less frequent than that without proper "pickling" and I'd be concerned and definitely price it as a run-out. At only 35 hours per year, it is likely it sat too long without an oil change at least once.
 
Okay thanks everybody. I see there is some doubt with an engine that old. I will for sure look over the logs no doubt. I'm trying to get a buddy to go along with me who has some good knowledge in this as this is my first rodeo. I don’t mind it being 20 years old honestly as long as everything checks out. Because what a new engine just overhauled could just as easily crap out.
 
simtech said:
Thanks for the replies. I'm told no fragments in the oil, no burning of oil, I think he said 1 qt every 10 hours it is using. I might go look at it this weekend. It is a 71 Beech Sundowner. I have no problem around here getting non ethanol gas, just for how long...who knows. I know for the past 1 year or so it had been flown weekly, prior to that I'm not sure.
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If the current owner has been sending in oil samples for analysis, ask to see the reports. The data shown there (including dates and engine hours) will give you a good insight into engine health.
 
It all depends on how well you are on your other PM on the thing. Generally airplanes that can't make modest TBO hours in 12 years, tend not to have been flown regularly so they have other problems as well. Note there are frequently things (especially anything made of rubber) that aren't dependent on the number of hours or what kind of compression readings you're getting that you may wish to look at if you decide to forego the overhaul.

My aircraft was someone of a hangar queen when I bought it. 500 hours in the past 13 years or so. Amusingly, around 1997 I pulled off a rubber fuel line and the mechanic told me to clean off the ends of it and see what the date code was. 1948. The hose was two years older than the airplane and never been replaced. It made a scary crackling noise as I straightened it out so I could measure how long it was to get the replacement.
 
simtech said:
Okay thanks everybody. I see there is some doubt with an engine that old. I will for sure look over the logs no doubt. I'm trying to get a buddy to go along with me who has some good knowledge in this as this is my first rodeo. I don’t mind it being 20 years old honestly as long as everything checks out. Because what a new engine just overhauled could just as easily crap out.
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Just get it checked out, I've seen engines need expensive repairs after just a few years of neglect and others, like mine have gone 30 years without a hick up.
 
AggieMike88 said:
If the current owner has been sending in oil samples for analysis, ask to see the reports. The data shown there (including dates and engine hours) will give you a good insight into engine health.
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Oil analysis is great and can be a harbinger of engine ails. But it's not the cure all, end all.

Example:

Two years ago, I flew my plane up to another airport for it's annual. It was winter and I was a week early because the forecast was going downhill and I didn't want to get boxed out. So we drained the oil and let it sit for a week.

When I returned a week later to assist with the annual, I already had the oil analysis back (Blackstone).

"Well, everything looks great in the oil analysis" I said to the A&P.

"Really? Did they tell you about #4 only making 38#?" he replied.

"Ummmmm....." :redface: :mad:
 
This is the stupidest quote I have heard in a while.

Does he use a stethoscope to check the color of paint as well?

timwinters said:
Oil analysis is great and can be a harbinger of engine ails. But it's not the cure all, end all.

Example:

Two years ago, I flew my plane up to another airport for it's annual. It was winter and I was a week early because the forecast was going downhill and I didn't want to get boxed out. So we drained the oil and let it sit for a week.

When I returned a week later to assist with the annual, I already had the oil analysis back (Blackstone).

"Well, everything looks great in the oil analysis" I said to the A&P.

"Really? Did they tell you about #4 only making 38#?" he replied.

"Ummmmm....." :redface: :mad:
Click to expand...
 
timwinters said:
Oil analysis is great and can be a harbinger of engine ails. But it's not the cure all, end all.

Example:

Two years ago, I flew my plane up to another airport for it's annual. It was winter and I was a week early because the forecast was going downhill and I didn't want to get boxed out. So we drained the oil and let it sit for a week.

When I returned a week later to assist with the annual, I already had the oil analysis back (Blackstone).

"Well, everything looks great in the oil analysis" I said to the A&P.

"Really? Did they tell you about #4 only making 38#?" he replied.

"Ummmmm....." :redface: :mad:
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Did he get the compressions on a cold engine?
 
BillTIZ said:
Did he get the compressions on a cold engine?
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Hot, cold, everywhichway,

We took four readings during the course of annual. The highest was 41. We pulled the cylinder and had Seth (PAP) O.H. it. Bad exhaust guide.
 
Kyle this is not true. There is plenty of mogas without ethanol at least 85% of the country has it. The exception is places where you cannot find it.

kyleb said:
The 12 year number is a Lycoming recommendation, but most overhaul engines on condition, not hours or years.

The mogas STC depends on the airframe/engine combo. What is the aircraft? Today's problem with Mogas is that so much of it has ethanol, and you can't <legally> use that in an airplane anyway, so the STC is largely moot.
Click to expand...
 
So I went and looked at the plane this weekend. It was very nice with lots of new avionics. The engine appeared to be strong, the exhaust was not sooty and the oil was clean. I looked over the engine log and it was since new. I saw the overhaul was accomplished in 1994 and has since put on 654hrs. The engine made it past TBO the first time and currently it is getting an oil change every 6 months. Other than that nothing major has ever happened to the engine or the airframe. I did notice some putty looking stuff in the door jamb but I didn’t ask about it. Otherwise, if I go for it, ill likely have it bore scoped. The compressions are in the mid 70's and the last oil analysis came back clean.
 
Tony_Scarpelli said:
Kyle this is not true. There is plenty of mogas without ethanol at least 85% of the country has it. The exception is places where you cannot find it.
Click to expand...

Finding it in the appropriate grades can be a challenge. There are some areas where you won't find the 93 octane without ethanol (oddly enough we have some stations here where only the 93 is ethanol free).
 
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