Years Since Overhaul

Lowflynjack

Lowflynjack

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Jack Fleetwood
I'm sure I already know the answer to my question, but thought I'd open it up for discussion anyway! When we talk about SMOH, we always talk about hours. We want to know many hours until TBO, or how many hours since major overhaul.

I've heard over the years that an engine sitting and not being flown is worse than one with higher time. I've always flown a lot and never had any real engine issues, so my flying seems to lend credit to this theory.

I like a plane that is for sale right now and could see myself owning it, but it's got 72 SMOH, which was done in 2005. It's essentially a new engine, except that it was overhauled in 2005, so flown about 4.5 hours per year average. It has an O-300D and the TBO is 1800 or 12 years. This one has 16 years on it and was barely flown.

Another plane I like has an O-470-R and has 1400 SMOH that was done in 1993, so around 50 hours per year, which is good, but TBO is 1700 or 12 years.

I hate airplane shopping! I'll probably spend more money than I spent on my first house. I want to avoid as many potential issues as I can.
 
I'd say it's probably fine as long as they didn't do the "ground run it every 3 months" for the past 12 years. I have nothing to support that with, but if it's just been sitting it's hard to get much moist air in it to support corrosion. Remember that all of the rubber components like fuel hoses and such will certainly need to be replaced/inspected due to time limits.
 
From my experience (one airplane fwiw), I’d go for the one with the O-470, IF you can get it for a price that reflects a possible imminent OH.

The other one, regardless of low TSOH, may very well start making metal 1, 5, or 100 hours into your ownership, yet you’re likely to pay a premium because everyone focuses on TSOH, not calendar years.

My personal experience was that I bought a C182 with a mid-time (650-ish hour) engine and dated avionics, believing that the mid-time engine would buy time and $ for avionics. Unfortunately, I started making metal in the high 700’s, so that plan proved ill-fated. To add insult to injury, I passed on a newer 182 with a gorgeous panel, interior, paint, and regular flying and Mx history to buy mine because that one was 100 hrs past TBO. Oops.
 
Omalley1537 said:
To add insult to injury, I passed on a newer 182 with a gorgeous panel, interior, paint, and regular flying and Mx history to buy mine because that one was 100 hrs past TBO. Oops.
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I understand this decision! There's a 182 I like that is $45K more than the one with 1400 SMOH. It's a lot of money, but has a new engine and prop, which would cost me a fortune. That sure is a lot of money though!
 
The difficulty is that when you see a plane for sale with engine at TBO, the owner is forced to mark down the price to account for the fact that the engine will need an overhaul. When the engine is 72 SMOH, but it was done 12 years ago, the owner will dig in their heels and claim that the engine is "like new", and price it accordingly. Good luck getting them to discount the price to the point where an overhaul becomes affordable.
 
I've done the same thing looking at airplanes for sale that I can't afford. A little while back I saw a Cherokee for sale. Engine overhauled in ~2000 and it had less than 10 hours. They were advertising it like it was a brand new engine. The owner had the overhaul done, flew it home, and then let it sit for 20+ years.

Contrast that with the airplanes I rent. They fly 50 - 100 hours a month. They reliably fly dozens of different pilots around nearly every day. But at that rate, the plane will need an engine overhaul almost once every two years. I know which airplane I'd rather be flying.
 
depends....I have one that was done in 2004 and it's pristine inside. It has relatively low usage over that time period.....less than 1,000 hrs usage. So, it sat.
 

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Airplane engines are vented. There’s a free path for moisture to get in while parked. Engines are timed out at 12 years. That low time motor is a core. You may get some time out of it but don’t bet your money on it.

It’s almost always money well spent to buy the airplane with the equipment you want, whether avionics, motor, or mods. If you buy a fixer-upper and spend a bunch of money your return on investment will be around 50 cents on the dollar. Let the seller take that hit and buy the better plane.
 
Without looking at it, it’s really a crapshoot. The advice that I’d offer, is that the engine might be fine, but the accessories and hoses might need to be refreshed. If you’re serious about buying it, my advice would be the usual - borescope what you can, see what you can see and then roll the dice.
 
There's way more to the whole thing than time or calendar time. An engine with 500 hours overhauled 5 years ago could be total crap, and an engine with 1000 hours overhauled in the 70s could be running like a top in perfect condition. Depends on how it was run, where and how it was stored, and, frankly, a little/lot of just pure luck. Any engine should be viewed skeptically until an inspection is performed (borescope it, etc.).
 
I'm preaching to the choir to say that airplanes are costly. I try to spend the money in a way that trends towards reliability. I'd rather have the old engine overhauled as opposed to an owner trying to sell me a "newly overhauled 20 years ago engine" with a handful of ground run hours on it.

Get a steep discount on the sale of the aircraft (if possible) and spend it so that you know the condition of the engine after it comes back from the shop.
 
  1. I picked up a 1968 Cessna with an O-320 1500 hours total time since manufactured in 68, purchased it in 1989 and it had been sitting unflown for 5 years. It still had good compressions when I purchased it Offered a reduced price anticipating a certain overhaul, flew it for another 1000 hours and 10 years checking oil and compressions and at 2500 hours I got nervous flying out over the swamps to KNEW. So when I got home from that trip we pulled it and did a field overhaul, the Engine builder showed me the bearings and cylinders, stated he believed it would have gone another 1000 hours.
 
I own and fly an O-320 Lycoming that was assembled at the factory in 1970 and has never been apart. Its at about 1100 hrs total like the plane it pulls around, has seen long periods of inside storage, but continues to function well. Three of the cylinder bores have a little corrosion when viewed by borescope but it burns a quart every 12 hrs, has good compression and doesn't leak. Every time I think I should overhaul it, I go fly it and it performs as well as a new one... so I wait. I've been doing this for 10 years and maybe 300 hrs.
 
Last October I bought a Cessna 172 with about 1100 hours on an O-300D engine, but it basically sat unused for about 8 years. Prebuy/annual went well with no issues from an independent AP/IA. The previous owner had annuals done each year and ran it about 10 hours over those 8 years. It was in Wyoming where the climate at the home field is basically desert, so pretty dry (not humid) from what I could tell. I was a bit nervous as well, but the price was right. I now have 120 hours on it since I bought it, compressions in 70's, burns 1 Qt every 10 hours and the only thing to go south on it was a magneto. I have since replaced both mags, and spark plugs but the engine runs great...so far at least. I am pleased with it.
 
Yes, I think it depends on particulars, but I’d be suspect with long idle periods. I’d want the price adjusted somewhat for those idle years, possibly hard in this sellers market.

I looked at a plane about 7 years ago, priced at $125k, with a 30 year old factory engine, 1500 hours. The heirs of the deceased pilot said it was worth more because nobody screwed with the engine from the factory. It was actually worth it with the 1500+ hour, 30 year engine.

I liked the plane but passed, plenty of emotion tied in. They sold it almost 2 years later for $82k. I would of bought in the mid 90’s.
 
sourdough44 said:
Yes, I think it depends on particulars, but I’d be suspect with long idle periods. I’d want the price adjusted somewhat for those idle years, possibly hard in this sellers market.

I looked at a plane about 7 years ago, priced at $125k, with a 30 year old factory engine, 1500 hours. The heirs of the deceased pilot said it was worth more because nobody screwed with the engine from the factory. It was actually worth it with the 1500+ hour, 30 year engine.

I liked the plane but passed, plenty of emotion tied in. They sold it almost 2 years later for $82k. I would of bought in the mid 90’s.
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Emotion can definitely cause issues in a sale. Tried to buy a plane where the guy lost his medical and wasnt able to get it back. Chatted on the phone many times and finally came to a handshake agreement and planned to get the prebuy done and he all of a sudden got cold feet and decided he wanted to keep it. Never has sold it since...just sad for all involved.
 
caveat: I'm not an A&P, etc

Doesn't the manufacturer have a calendar life limit on engines? iirc, the lycoming O-320 is 12 years. We also have to consider the condition of the hoses, wiring, and gaskets, yes?
 
Calendar time as well run time are arbitrary limits agreed to by the FAA for the purposes of part 135 operations (they are not a statistical representation of what wears - they are a sample size of one and run aggressively to 150 hrs).....and do not apply to most of our operations....part 91. Many times the 135 ops docs get extended...and extended.

Hoses, wiring and gaskets should be replaced periodically as a result of the annual inspections.
Bob Noel said:
caveat: I'm not an A&P, etc

Doesn't the manufacturer have a calendar life limit on engines? iirc, the lycoming O-320 is 12 years. We also have to consider the condition of the hoses, wiring, and gaskets, yes?
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Bob Noel said:
calendar life limit on engines
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Its not an airworthiness limitation life-limit but rather the calendar side the OEM recommended overhaul schedule. It carries no more clout than the hourly based recommendation.
 
Our '57 Cessna 172 was rebuilt in the mid 80s. We bought it two years ago with just under 1500 hours on the O-300C. It was flown almost every year but there were years when it was only 10-15 hours. Since we bought it we have put a 134 tach hours on it. Still seems to run good I suspect (although who really knows) we will make TBO and beyond. That is the good news.

The bad news is we have put 3 cylinders on it since we owned it and there was a 4th put on about a year prior to our purchasing it. So yay almost a top overhaul. Funny the back two cylinders are still hanging in there. What we can see of the cam when we pull the cylinders looks good. The cylinders have had some pitting so I suspect that is what is causing the rings to wear.

It is a crap shoot and any engine could let go the next time you fly it.
 
Well, unless something changes, I've made a deal on a plane where the engine is being overhauled by JB Aircraft right now. It was the right choice and I'll pay a little more for the plane, but in the long run, it was the right choice for me.

Hopefully I'll be announcing 'Photo Plane 1' here! Thanks for all of the input. I knew the answer before I asked the question, but the reassurance sure helps!
 
Congratulations on making the deal! So the big question is "will you let someone else fly it so that you can take your awesome air-to-air shots of your new plane or do you have a colleague who will take photos of you flying it?"
 
rsleeds said:
Congratulations on making the deal! So the big question is "will you let someone else fly it so that you can take your awesome air-to-air shots of your new plane or do you have a colleague who will take photos of you flying it?"
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He has a drone now, so he'll just take pictures of himself flying it. :)
 
Although you always hear about the rusted out engines on the internet, it's been my personal experience that it's not a given. Especially for Continentals; the cam is not overhead and stays better lubricated. My current engine was overhauled after sitting for 12 years and had not a spot of rust on it. So it really depends.

You can pay a mechanic to take a look, including pulling a jug to look at the cam, if you really want to. At the end of the day, it's always a calculated risk.
 
Lowflynjack said:
Well, unless something changes, I've made a deal on a plane where the engine is being overhauled by JB Aircraft right now. It was the right choice and I'll pay a little more for the plane, but in the long run, it was the right choice for me.

Hopefully I'll be announcing 'Photo Plane 1' here! Thanks for all of the input. I knew the answer before I asked the question, but the reassurance sure helps!
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is that jb in sebring fl? if so, jimmy is a great guy and builds a great engine. I have one of his in my warrior.
 
rsleeds said:
Congratulations on making the deal! So the big question is "will you let someone else fly it so that you can take your awesome air-to-air shots of your new plane or do you have a colleague who will take photos of you flying it?"
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Good question... not sure!
SoonerAviator said:
He has a drone now, so he'll just take pictures of himself flying it. :)
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Good idea though... just set the drone on video and fly by it over and over!
 
samiamPA said:
Although you always hear about the rusted out engines on the internet, it's been my personal experience that it's not a given. Especially for Continentals; the cam is not overhead and stays better lubricated.
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The position of the cam makes little difference to lubrication, since oil is being flung off the crankshaft in all directions. About the only thing it would gain is some dripping off the crank for a few minutes after shutdown, and the cams themselves would get oil dripped on them only if the rod journals stopped directly over them. The Lycoming's cam in the top of the case suffers because it's near the outside wall and it cools quickly, letting water condense on it. Oil pan heaters can drive evaporation of any water in the oil, and it then condenses on the cam as well.
 
I think it's smart you went the route you did. To me, the other way is kind of like playing a reverse lottery on the engine...fine if you can afford it, I suppose, but a risk. I'd be more comfortable going the other way, an airplane with high time, low calendar, and running it longer than recommended hours. Maybe as more pilots learn that sitting idle isn't good for an engine, the search for low hours since overhaul may be switched for 'months since last overhaul'.
 
BTW, many constant-speed props also have both TBO and calendar years between overhaul
 
Albany Tom said:
I think it's smart you went the route you did. To me, the other way is kind of like playing a reverse lottery on the engine...fine if you can afford it, I suppose, but a risk. I'd be more comfortable going the other way, an airplane with high time, low calendar, and running it longer than recommended hours. Maybe as more pilots learn that sitting idle isn't good for an engine, the search for low hours since overhaul may be switched for 'months since last overhaul'.
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Either option is fine as long as they are priced as such.
 
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