How long should an engine last?

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Johnbo

Pre-takeoff checklist
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Johnbo
Ok, very subjective but I am trying to get some averages on what to expect and when. As I shop for a family plane, I find tons of examples with low or mid time motors but when it comes to calendar time most have 20-25 years SMOH. Compressions are always great but it is the cams, lifters, etc that I figure will rust and start making metal first.

Should I be fully depreciating the value of these 20-year motors while I work on offers? How long will a motor typically go if it is flown (not ground run) once every week or two for an hour or so (50 hours / year)?

thx
 
I recommend getting it as cheap as possible regardless of condition and if the engine is out of warranty have a plan to cover replacement/overhaul of the engine the day after you buy... just in case.
 
Treat the engine nice and hopefully it will go to TBO and beyond. How many hours do you expect to fly each year?
 
First a plane that has not flown is better to just sit and not start up... Starting and running on the ground creates moisture....
My Skybolt has a 540 off a Aztec. It runs perfect and does not leak a drop of oil. That engine has never been overhauled and now has 2000 hours on it. It has never had a top overhaul or cylinder replaced..... All the factory cylinders have 2000 hours on them. I would not think about overhauling it anytime soon.
Its a crap shoot. That engine has made it to TBO and is still excellent.
I had another 540 come apart with 400 hours on it.
Flip a coin. You never know.
 
Waaaay too many factors. Perfectly good engines can get early termination by a mechanical failures on other parts of the airframe and then there are those engines that go 3K hours while an identical engine might not make TBO. I've had an engine go south about 150 hours before TBO that IMO was treated very well - flown weekly on cross-countries and carefully managed but a crankcase crack showed up (the engine didn't fail, we found the crack after an unveventful flight home but saw the oil leak and grounded it). Another generally reliable engine suddenly started consuming oil at a high rate and it seemed a better choice to go with a full overhaul rather than fixing 2-3 pistons / rings. I've seen very student-abused Skyhawks and Tomahawks with really high engine hours, too.
 
I agree that it’s a crap shoot. General rules though- in my experience, you want to see as close to at least 100 hours a year on a engine as you can get. Sitting is terrible for engines. Of course humidity is too. The simpler the better. Turbocharger is nice, but they tend to not make it to TBO. 3/4 of the way there seems typical, even running it cool as reasonably possible, and when they blow they take the engine with it. My motto is- figure out what you can reasonably afford to own, and then step it down 1(or better yet 2) level/s if you can make it fit your mission. I do this with cars too. This gives you wiggle room for the surprises, like a top overhaul after 300 hours.
 
My Skybolt engine I talked about above has flown 300 hours since 1991...
1700 hour engine was put on a brand new airframe in 91 and it now has 300 hours airframe and 2000 engine.
So again, saying the must fly 100 hours a year is crap...
 
pigpenracing said:
My Skybolt engine I talked about above has flown 300 hours since 1991...
1700 hour engine was put on a brand new airframe in 91 and it now has 300 hours airframe and 2000 engine.
So again, saying the must fly 100 hours a year is crap...
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Not going to argue. To each, their own.
 
pigpenracing said:
My Skybolt engine I talked about above has flown 300 hours since 1991...
1700 hour engine was put on a brand new airframe in 91 and it now has 300 hours airframe and 2000 engine.
So again, saying the must fly 100 hours a year is crap...
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10 hours a year? You need to fly the thing more!
 
RussR said:
10 hours a year? You need to fly the thing more!
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I just got it 3 months ago... The builder I got it from is 89 years old now.
I’ll fly it more than he did but I have 6 in the hangar to keep flying... I rotate which ones I fly.
 
Compression test are fine for determining wear but almost useless for determining condition. You are checking compression at one point in the piston stroke. There could be rust pitting at other points in the stroke. It really is a crap shoot though. The engine in my venture sat for 17 years and has not had a problem for the past 400 hours. The engine on my Cessna sat for 15 years and is on the way out. You would have better luck with a high time recent overhaul than one that has sat for extended periods depending on location. The only exception is an airplane that has been used for training or in a flight school.
 
How long is a rope?

The variables are too numerous to make the prediction useful. Once you have spent time with a particular engine you can come up with a better guess, but an unfamiliar engine could be anything. Compressions only indicate to you the condition of the top end. The rest of the engine could be worn out and not be indicated by a compression test.
 
Who did the overhaul, a large well known shop, factory overhaul or Joe at the local airport that everyone says does great work. Factory and large shops stand behind their engines if it's a local will he make good on a engine 2 or 3 thousand miles away. Just what kind or warranty goes with the engine. Those that never have any problems with their engines from cradle to grave are happy campers others pay and some pay a high price.
 
brien23 said:
Who did the overhaul, a large well known shop, factory overhaul or Joe at the local airport that everyone says does great work. Factory and large shops stand behind their engines if it's a local will he make good on a engine 2 or 3 thousand miles away. Just what kind or warranty goes with the engine. Those that never have any problems with their engines from cradle to grave are happy campers others pay and some pay a high price.
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There isn't a shop around that will stand behind a 20 year old engine. Most are only warrantied for 2-3 years max. Nothing complicated about building up an engine, I would be more concerned that all the parts were sent off to reputable shops for inspection and refurbishment. But again, after 20 years none of that really matters.
 
There is no way to know how many additional hours you can expect a mid-time engine to safely run. Any airplane owner should be prepared to overhaul or replace the engine at any time, and purchase accordingly.
 
The two factors that get the most focus seem to be time running, %TBO and wear impact and time sitting, potential corrosion. It would also be interesting to look at the impact of dynamic balancing. No impact on engines that sit, but potentially an impact on high time engines. I doubt there is any real data to show how vibration affects engine life, but there's a lot of focus on it in preventative maintenance of industrial equipment.
 
Johnbo said:
Ok, very subjective but I am trying to get some averages on what to expect and when. As I shop for a family plane, I find tons of examples with low or mid time motors but when it comes to calendar time most have 20-25 years SMOH. Compressions are always great but it is the cams, lifters, etc that I figure will rust and start making metal first.

Should I be fully depreciating the value of these 20-year motors while I work on offers? How long will a motor typically go if it is flown (not ground run) once every week or two for an hour or so (50 hours / year)?

thx
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from the asset value standpoint? Engine manufacturers establish limits for hours in service AND calendar years. While those limits aren't enforced for private operators they should be considered in the valuation of an airplane.
 
MBDiagMan said:
How long is a rope?

The variables are too numerous ...
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And just like rope, usually just long enough to trip over or hang by.

Short of purchasing brand new... The only way CYA 100% is to have double what you intend to spend on an airplane.

If the plane you are considering is $100K, you probably ought to have $200K to start.

Nobody does that.

But, if you want to be CERTAIN that you will always have a plane at your disposal, and something not covered by insurance occurred to yours, you'd need money to replace it on a moment's notice.

Unrealistic? Yep.

Even new, covered by warranty, it gets repaired, not replaced. You may, or may not, get a loaner.

Sorry, few guarantees in life. You spends your money and you takes your chances.
 
CharlieD3 said:
And just like rope, usually just long enough to trip over or hang by.

Short of purchasing brand new... The only way CYA 100% is to have double what you intend to spend on an airplane.

If the plane you are considering is $100K, you probably ought to have $200K to start.

Nobody does that.

But, if you want to be CERTAIN that you will always have a plane at your disposal, and something not covered by insurance occurred to yours, you'd need money to replace it on a moment's notice.

Unrealistic? Yep.

Even new, covered by warranty, it gets repaired, not replaced. You may, or may not, get a loaner.

Sorry, few guarantees in life. You spends your money and you takes your chances.
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Yep! This is also why there are so many derelict airplanes sitting around rotting away. If someone overpays with the expanse of knowledge available to anyone with a phone it’s hard to feel sorry for them. Im a firm believer in the seller paying for their neglect or use and not the buyer.
 
Grum.Man said:
Compression test are fine for determining wear but almost useless for determining condition. You are checking compression at one point in the piston stroke. There could be rust pitting at other points in the stroke. It really is a crap shoot though. The engine in my venture sat for 17 years and has not had a problem for the past 400 hours. The engine on my Cessna sat for 15 years and is on the way out
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My O-320 has compression above 76/80 on all cylinders (obviously at TDC) with some corrosion visible at mid-stroke on three of four. It was assembled in 1971, has never been disassembled, uses a quart every 12 hrs, leaks only tiny bit of oil at the base gaskets, and has 1100 hrs or so tach time. I have no idea what to do except fly it and watch it...
 
pigpenracing said:
My Skybolt engine I talked about above has flown 300 hours since 1991...
1700 hour engine was put on a brand new airframe in 91 and it now has 300 hours airframe and 2000 engine.
So again, saying the must fly 100 hours a year is crap...
Click to expand...

Since you only got the plane 3 months ago (according to your other post), I’d say it’s way to early to be celebrating...it could take hundreds of hours before you will notice anything.
And oil analysis may not give you any indication of a problem.

Tom
 
Tusayan said:
My O-320 has compression above 76/80 on all cylinders (obviously at TDC) with some corrosion visible at mid-stroke on three of four. It was assembled in 1971, has never been disassembled, uses a quart every 12 hrs, leaks only tiny bit of oil at the base gaskets, and has 1100 hrs or so tach time. I have no idea what to do except fly it and watch it...
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Other than routine oil filter cutting and oil analysis there is nothing to do really. I think Lycoming stated somewhere in an article I read that an engine with Corrosion pitting could still hold up 2-400 hours after the corrosion started. I have surpassed that in the venture but the Cessna is making a good bit of metal at 250 hours in service since it's extended rest.
 
Thanks for that, haven’t done an oil analysis recently but there’s is zero metal in the filter so I’m planning to just fly it for a while at least. If it were to have 400 more hours in it, that’s quite a long calendar period and would get me to 1500 hrs since new in 1971.
 
I know of at least one O-320 that was assembled in 1967 getting close to 2000 hours since new, three of four cylinders are original. It runs fine but has had carb, mags, harness, spark plugs, fuel pump, hoses, and other stuff replaced. I'm planning on tearing this one down myself at some point so it should be interesting, then again it may be boring lol.

There was another one on the airport from 1981 that was original till last year, they wanted power so did a 180 upgrade.
 
I get flamed anytime this is mentioned, but calendar time does matter. Most of us replace or overhaul engines on condition. Corrosion happens in all climates, and much more so in others. Buying a plane, one should consider an engine with more than 20 years since new or O/H a point of negotiation. The service bulletins for the years get satisfied during overhaul, and likely at least one bulletin over 2-3 decades.

Inspection of lifters and cam lobes is more prudent on low time per year engine operation.
 
pigpenracing said:
My 400 hour 540 in the Christen Eagle let loose on climbout. I had just enough altitude to turn and make a safe landing on the runway.View attachment 82149 View attachment 82150
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WOW! Very glad you got back OK and was able to tell the story.

Was the engine a Lycoming? Wonder if the break is related to the other big block Lycoming crank AD Cessna went through?
 
TBO is only a manufacturers recommendation. It is not regulatory. That is for both engine hours and calendar time.
Their recommendations are for worst case scenarios. Such as not flown often and kept outside in a corrosive environment.
If compression is good and there are no signs of a need for tear down then there is no need to disassemble a perfectly good working engine.

An older motor would usually be priced accordingly. Also, ground run is terrible as the engine does not get up to its full operating temperature. Engines will produce internal moisture on the ground. Better to not start it at all unless going to fly.
 
Electrons are cheap so tell us where you will be based. I live in the Arizona high country and my IO-520 often sits months without flying but no corrosion. I know this because I do my own overhauls and the camshaft and lifters are fine. The weak point has always been exhaust valves so you may need to pull a cylinder or two before TBO to get new seats, guides and often a good used valve.

I find it laughably illogical to say to fly your plane once a week just to prolong its life unless you are looking for an excuse to fly. Sure your engine will last more hours but you wasting more hours and fuel going nowhere. And these are the most dangerous hours: takeoff, landing and midair collision risk.
 
Snowmass said:
Electrons are cheap so tell us where you will be based. I live in the Arizona high country and my IO-520 often sits months without flying but no corrosion. I know this because I do my own overhauls and the camshaft and lifters are fine. The weak point has always been exhaust valves so you may need to pull a cylinder or two before TBO to get new seats, guides and often a good used valve.

I find it laughably illogical to say to fly your plane once a week just to prolong its life unless you are looking for an excuse to fly. Sure your engine will last more hours but you wasting more hours and fuel going nowhere. And these are the most dangerous hours: takeoff, landing and midair collision risk.
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Once a week maybe excessive but it's also laughably illogical to own a plane and not fly it at least a few times a month. If not to preserve the machine, to preserve your safe piloting.
 
Flight schools seem to be king when it comes to getting high times out of their engines. Flown perhaps an average of 3-4 hrs a day and oil changed every 50 hrs, it's no mystery how they get the most time out of their engines. Rather incredible, really, since students account for much of the time put on those planes.
 
Johnbo said:
Should I be fully depreciating the value of these 20-year motors while I work on offers?
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There are no set "depreciation" schedules for non-tracked components or aircraft. What I have recommended to owners when performing pre-buys is look at the whole aircraft when developing an offer as each aircraft is unique. Lumping high time engines (calendar or hours) or panel configurations into in category may not fit the airframe you are considering or want. The best advice is discuss any aircraft with the APIA that will maintain/annual your aircraft before you pre-buy or purchase. His input will carry more weight than any others as he will be the one who presents you with that 1st discrepancy and bill to fix your "new" aircraft.
 
MooneyDriver78 said:
Since you only got the plane 3 months ago (according to your other post), I’d say it’s way to early to be celebrating...it could take hundreds of hours before you will notice anything.
And oil analysis may not give you any indication of a problem.

Tom
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Well it is at TBO and I am flying it so I am happy.. Not using or leaking any oil.
If it quits tomorrow i will put a engine in it. If it goes another 1000 hours I am extra happy.
It is a aerobatic plane so most my flights are about 20 minutes with a occasional lunch run..
 
christen 1.jpg eagle advanced.jpg View attachment 82176 View attachment 82175 View attachment 82175
NordicDave said:
WOW! Very glad you got back OK and was able to tell the story.

Was the engine a Lycoming? Wonder if the break is related to the other big block Lycoming crank AD Cessna went through?
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No crank AD...
The engine was hopped up with 11:1 pistons and more RPM. It was flown pretty hard from the guy I got it from.
He made the USA Advanced aerobatic team flying it. It was not babied.... It just happened to take a crap a week after I bought it.
 
Grum.Man said:
Once a week maybe excessive but it's also laughably illogical to own a plane and not fly it at least a few times a month. If not to preserve the machine, to preserve your safe piloting.
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So you find using a plane primarily for travel to be illogical but burning finite, expensive resources go in circles logical. Hmmm, very bizarre logic.
 
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