So, What about high time engines?

[DaV8or]

I have located a plane that has what looks to be an excellent low time, all original airframe with some nice avionics in it, but it has a high time engine. Here are the known info on the engine;

It was a factory new Lycombing engine in 2000. After about 1300 hours, it developed low compression on one cylinder. They pulled it and determined the cam looked good, so the owner opted to redo all four cylinders. The bores were redone at Penn Yang and installed by the local A&P with new rings but original in spec pistons. The engine is now at a little over 1700 hours. Compressions are reported to be high and oil consumption low. (one quart per 10 hours) In my inexperienced mind, this engine is still only 300 hours from needing major money.

The problem is, the overall price of the plane is higher due to the very nice airframe and avionics. I can make this plane meet my stated mission goals with in budget in all perameters except one, a mid time or lower engine. Is it wise to run an engine past TBO? Because this engine has a somewhat reconditioned top end and has been inspected only 400 hours ago, is it reasonable to expect to push it past TBO with confidence? I really don't want to spend enough to get the plane I want it AND buy a new engine in about 3-4 years. What I should I do? To see this plane requires a trip well out of the way and I'm going to Texas this weekend where it is and have limited time, so I need to make up my mind.

Thanks for the help.

[mooneygirl]

You ask some really good questions Dave.  When we were looking and found the Ovation it had what most would consider "high time."  About that time we went to see a Mike Busch seminar about TBO just being a number. It was very informative.  Mike said something that has stuck with me.  "take care of the bottom end.  Everything else with a bolt is an accessory.  If you need a new accessory [cylinder] just unbolt it and put another one on."  I realize that this idea is a bit out of the norm.  He reinterated that with good maintenance, and flying the heck out of the plane, you can expect to go well over TBO.

With our purchase we made sure to have a thorough pre-purchase inspection including borescope, valve wobble test and the normal things.  Since the plane passed with flying colors, we made an offer.  Because of the "high time" we got a good price.  We have had it over a year now, and it just came through annual very easily.  Our Ovation has always been flown lean of peak, and had regular oil analysis.  There aren't any guarantees out there.  My E model was a mid-time engine 700 hours.  But a year ago I needed to have an "accessory" re-done.  I thought I had ten more years on that engine, but you never know.

I kind of like the idea that TBO is just a state of mind, as long as your oil analysis, and compressions are good.  Good luck in your hunt. It was very nice to meet you on Saturday.  Look forward to seeing you at L52!

 

http://www.savvyaviator.com/

[DonMuncy]

From what I have been told, most engines at overhaul have virtually nothing wrong with the "bottom" of the engine. Therefore, with good compression, good oil consumption and good oil analysis data, I think it likley you have far more than 300 hours and possibly anther 1300 hours before you should expect to have to do it. Naturally, you don't want to pay for the plane like it had 1000 hours left, but I would pay substantially more than it would for one with a run-out engine.

Don   

[KSMooniac]

Your post describes almost exactly my experience buying an engine at 1400 SMOH (1991, factory OH), followed by low compression on 2 jugs last year at 1650 SMOH.  I pulled all 4 jugs for IRAN work and ended up with 4 new pistons, 1 new exhaust valve, new guides, rings and honing.  I now have excellent compressions, low oil use, good oil analysis, and plan to keep running past TBO as long as everything is good.  (Jolie's post is spot-on, too!)

My plane had lots of other advantages too like NDH, regular use, nice upgrades, etc. so I was fine with the engine time.  I'm still happy with my choice, even though I had to put a few AMUs into the plane last year...but now I have more of a known quantity and higher confidence to run past TBO.  Your candidate plane sounds very, very similar, except someone else put in the AMUs instead of you!  The upside is that for the same purchase price, you get "less" engine and "more" avionics or upgrades, or just a lower price scaled down by hours under TBO.  If you fly past TBO, it is sorta like bonus time, and with the recent work, you likely have a very good chance of it flying past TBO.  If you are completely honest with yourself, you still have to "pay" for the engine sooner or later, either by doing an OH on your watch, or reducing the sales price accordingly when you sell or trade thus it doesn't make a huge difference what the engine hours are when you get a plane IMO.

Having said that, some folks prefer a recently overhauled engine, while some want a runout so they can OH it to their own spec, and some are in between as you are.  If I did it over, I wouldn't change a thing...I got a proven engine without a bad cam, crank or cylinders (see any of the recent ADs) that I could fly for some years before needing an overhaul.  A recent OH would have cost additional money at purchase and still been a crapshoot in quality.  A runout would likely require near-immediate overhaul since I wouldn't have any history or confidence with the engine.

One last comment, when looking for a 30+ year old plane, the likelihood of finding everything on your wish list in a reasonable time frame (months), within your budget, and when you're ready to buy is fairly low, so you must be ready to compromise on some aspect of the wish list.  IMO, engine time is the best place to compromise....so if the rest of the plane meets your criteria and checks out in the pre-buy, then go get it!

[WardHolbrook]

It's a roll of the dice. It's one thing to take a busy, well monitored, flight school airplane past TBO, but trying to get another couple of hundred hours or so out of a run-out personally owned, infrequently flown (less than say 200 hours/year) is something else. It could very easily turn out to be false economy if those extra hours result in additional costs come overhaul time. Score a $12K crankshaft to the point that it's not salvageable and then calculate what those extra hours ended up costing you. I'm not saying that it can't be done prudently, but make sure you understand what the risks are vs the possible benefits. In most cases, you're just deferring the inevitable and even if you don't incure any significant additional expenses come overhaul time, your cost per hour is not changed my much. Is $1 or $2 per hour worth it? Not to me. 

[Kwixdraw]

Has any oil analysis been done? This would be a decision maker for me as long as there was enough of a history to see how it is trending.

[Ned Gravel]

DaV8or:

I agree with Jolie on this one. If you see the trend lines in Mike Busch' articles, engines at or near 2000 have relatively few instances of trouble - all other things being equal of course.

When I bought my E model it had 1630 hours on the engine and after research, especially with the Mike Busch articles and discussion with my AME, I was ready to go beyone 2000 hours, "on condition."  It was running very smooth, and all four jugs had been recently replaced.

It was only after the inspection of an oil leak at the bottom aft through bolt for number 2, did we have a closer look to find that the crank was binding when torque-to-spec was applied at that bolt.   The engine was talking to us and at 1963 hours and it was time.  It was pulled for the major.

Two weeks later the engine shop told us that the case had a 7 inch stress crack developing from the point of the oil leak.

After nearly 100 hours on the new engine, I still have another 100 or so to go before I feel as confident as I did before the engine started talking to me.  Post overhaul blues is another aspect of Mike Busch' writings.  The trend lines for problems are relatively high at this point in the engine's life.

Hope this helps.

[Mooney65E]

Low time airframe would be more important to me. As others have already stated the engine can be replaced easier than the airframe.  At an average of 170 hours per year you know that plane has been flown regularily. She's no "Hanger Queen" . That's a plus. Flying with a high time engine you'll always be wondering when it's going to go. Will it be on this flight??? Plan on spending money on the engine and work that into your negotiations. Best of luck and let us know what you decide.

[carusoam]

Nothing like a mid time engine to give you a good combination of economics and time to learn.  The lull between new engine challenges and old engine challenges.

The nice thing about low time airframes, the interior is not worn out and the log books are short.

The nice thing about high time airframes, the interior can be replaced better than new and the log books give interesting reading.

I have had both...

-a-

[DaV8or]

Well, I've decided to take the extra time to go look at this plane this weekend. I'll see if it lives up to the photos and check on oil analysis. I'll have a close look at the logs too. I'm still not sure how far past TBO I'm comfortable going. You have to figure that the TBO number was arrived at for a reason that presumably is based on experience and annalysis. The FAA clearly believes in the number as they require commercially operated planes to rebuild at TBO rather than just an inspection program. Oh, how I wish that airplane engines could somehow be magically as reliable and simple to own as a car engine.

[carusoam]

Quote: DaV8or

Oh, how I wish that airplane engines could somehow be magically as reliable and simple to own as a car engine.

[Piloto]

Quote: carusoam

 

Sir, your wish is my command....!

An M20C flies at 150mph and has a recommended TBO of 2,000 hrs.

All told it, will travel 300,000 miles before the suggestion / recommendation for a rebuild.

An M20R flies at 180 kts and has the same recommended TBO of 2,000 hrs.

All told, it will travel over 400,000 miles and the same suggestion / recommendation for a rebuild.

The M20R goes 33% further, but spreads the workload over 6 cylinders compared to 4 of the 0-360.

Carburetors, magnetos and generators are very simple to own and maintain.

Please remind me again how far my chevy is expected to go before the suggestion / recommendation is made for a rebuild?

What if it drove it at 150 mph and wide open throttle all the time?

There ya go, aircraft engines are now more simple and more reliable than automobile engines.

My humble thoughts,  (please let me know if I missed something in the math....)

-a-

[MooneyMitch]

I like it Piloto!

[The-sky-captain]

I've ran those numbers before using my J model speeds. It's pretty amazing when you think about it like that!

[KLRDMD]

"You pays yer money and you take yer chances."

I've had to overhaul an engine at 1200 hours (it got regular use). I have friends that have 2600 and 3600 hours on their respective engines and those airplanes don't fly regularly.

We just never know how much time we'll get out of a given engine; there are too many variables and unless we've owned and operated it since new, we don't have all the data.

[jmills]

Quote: KLRDMD

"You pays yer money and you take yer chances."

[140pilot]

My 20C was a high time ERAU plane. I got a lot of grief for buying something with a high time engine and airframe. She had around 7900TT and 1900 SMOH when I got it but she was very well maintained.  I never had a single significant issue with that plane and the engine ran flawlessly. I sold her with just under 2300 smoh on the A1D and would have flown her another couple hundred if I had not sold it. I just felt comfortable with the engine. I had friends with fresh overhauls that had 10 times the issues I had with my high time ride.