TBO - 4000 hrs?!

FlyingMonkey

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Was just perusing the online aircraft logs of some of my flight school's 172s. It lists the TBO as 4000 hrs. Just wondering if this is normal as I thought these mid 70s Lycomings were supposed to be 2000 hrs TBO. A few planes seem to be pushing 3000-3500 hrs with one at 4300 hrs and just now going in for an overhaul. It's possible the online log is not correct and just used for dispatching the plane. :dunno:
 
Correct - the TBO on those Lycomings is 2,000 hours. It's likely a misprint, or they're referring to how many hours they went between overhaul. O-360s can go well past TBO, especially if run regularly (i.e. in a flight school environment).
 
Rotax 912 series engines are a published TBO of 2,000 hours also, but several I know are well beyond 4,000 and still flying.

This is of course normally aspirated Lycoming engine correct?
 
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Just goes to show that the idea of the "abused, beat-up rental" may not be accurate.
 
Just goes to show that the idea of the "abused, beat-up rental" may not be accurate.

Well, there's a lot more to it than simply it being a rental.
 
Rotax 912 series engines are a published TBO of 2,000 hours also, but several I know are well beyond 4,000 and still flying.

This is of course normally aspirated Lycoming engine correct?

Yes Lycoming 0-320 normally aspirated, horizontally opposed, air cooled, direct drive.

So, is 2000 hrs TBO just a recommendation of when the engine should be overhauled or a requirement for safety? Should I be nervous flying an engine that is recommended to be overhauled at 2000 hours but is going on 4000 hours? Or are the 50 and 100hr inspections thorough enough to service the engine to be in good working order???
 
Yes Lycoming 0-320 normally aspirated, horizontally opposed, air cooled, direct drive.

So, is 2000 hrs TBO just a recommendation of when the engine should be overhauled or a requirement for safety? Should I be nervous flying an engine that is recommended to be overhauled at 2000 hours but is going on 4000 hours? Or are the 50 and 100hr inspections thorough enough to service the engine to be in good working order???


There is OEM recommended overhaul limits on everything. The O-320 is 12 years or 2000 hours whichever is first, which does not cover propeller or engine accessories such as magnetos, vacuum pump, etc. Whether or not you think its safe to fly more than double the hours passed is a decision only you can make.
 
Rotax 912 series engines are a published TBO of 2,000 hours also, but several I know are well beyond 4,000 and still flying.

I had not read that anecdote before. That's really impressive, given how many revs those things pull. (I recall 5,200?)
 
I had not read that anecdote before. That's really impressive, given how many revs those things pull. (I recall 5,200?)

Red line is 2 stages.

5800 RPM max for 5 mins max, then 5500 max continuous. You can run 5,200 - 5,500 all day long. The engine just seems to want to run hard, but you can pull it back to 4500 and loaf.
 
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Yes Lycoming 0-320 normally aspirated, horizontally opposed, air cooled, direct drive.

So, is 2000 hrs TBO just a recommendation of when the engine should be overhauled or a requirement for safety? Should I be nervous flying an engine that is recommended to be overhauled at 2000 hours but is going on 4000 hours? Or are the 50 and 100hr inspections thorough enough to service the engine to be in good working order???

Recommendation for Pt. 91, if on a 135 certificate it's mandatory.
 
I spoke to a guy that does overhauls.
He said that is a recommendation. If your engine is not telling you it needs an overhaul, keep flying but pay close attention to what the engine is telling you.
 
Recommendation for Pt. 91, if on a 135 certificate it's mandatory.

Not necessarily. Some 135s get approval for engines "on condition." However, that number is very few. Cape Air is one of them last I heard - and they were also getting 3000 hours out of TSIO-520s.
 
I spoke to a guy that does overhauls.
He said that is a recommendation. If your engine is not telling you it needs an overhaul, keep flying but pay close attention to what the engine is telling you.

That's my method, too. Flew the last set of engines to 400 past TBO. Could've gone longer, but engines were starting to tell me things (left engine, anyway) and the timing was good.

Hoping for 2,500 or 3,000 hours on this set (1700 TBO), but we'll see.
 
A warrior with mid 3000 hours on the engine finally stuck a valve. He could have just fixed the guide and gone on, but opted for a fresh engine at that point. Yes, it had been a flight school plane before he bought it.

4000 smoh could be, easily. It could have been IRAN with jugs being repaired one at a time as needed. The bottom end will cheerfully go 4000+. My engines had 1700 and 2300 on the bottoms respectively when I put brand new Titans on them and I expect the bottoms to keep on trucking till the jugs wear out.
 
Not necessarily. Some 135s get approval for engines "on condition." However, that number is very few. Cape Air is one of them last I heard - and they were also getting 3000 hours out of TSIO-520s.

Roger, but without that special dispensation, then TBO once again applies.
 
Roger, but without that special dispensation, then TBO once again applies.

Correct. For most 135s, engine and prop SBs are mandatory.
 
The flight school I ran would do 100 hr
per month and we would send engines out
For overhaul @ 2500 hrs. Overhauler kept
Asking why we were getting them overhauled.
Don't ever remember pulling a cylinder/ O-320's.
Dave
 
An engine flown regularly and maintained can blast through TBO with no problems. We had a Skyhawk that was up to about 2600 SMOH (and about 5000 total time) and still going strong until the owner finally relented from the badgering of the person operating the club and had it overhauled. Of course, it took us almost a month to get the kinks out of the overhaul (they broke the EGT in the process...not a big thing on a Skyhawk, etc...).
 
4300 hours just seems like a lot if the recommendation is 2000 hours. (Says a guy who skips recommended maintenance on his car all the time...) Just makes me nervous. Another vote for buying my own!
 
4300 hours just seems like a lot if the recommendation is 2000 hours. (Says a guy who skips recommended maintenance on his car all the time...) Just makes me nervous. Another vote for buying my own!

TBO isn't a magic number.

For example, there was a news story recently (sorry, don't remember where) about a company that makes parts for Lycoming engines...basically they make approved replacements for every part of the engine.

They were looking at assembling their own engine. Using the Lycoming design and already approved parts, they were told they couldn't get a TBO of >1,200 hours on it...remember, same design, same parts, just over half the TBO.

EDIT: Found the article:
http://blog.aopa.org/opinionleaders/2014/05/13/tbo-free-engine/

Jimmy is now working on taking ECi’s Titan engine program to the next level by seeking FAA approval for these engines to be used in certificated aircraft. In theory, this ought to be relatively easy (as FAA certification efforts go) because the Titan engines are nearly identical in design to Lycoming 320 and 360 engines, and almost all the ECi-built parts are already PMA approved for use in Lycoming engines. In practice, nothing involving the FAA is as easy as it looks.

“They told me the FAA couldn’t approve an initial TBO for these engines longer than 1,000 hours,” Jimmy said to me with a sigh. He had just returned from a meeting with representatives from the FAA Aircraft Certification Office and the Engine & Propeller Directorate. “I explained that our engines are virtually identical in all critical design respects to Lycoming engines that have a 2,000-hour TBO, and that every critical part in our engines is PMA approved for use in those 2,000-hour engines.”

“But they said they could only approve a 1,000-hour TBO to begin with,” Jimmy continued, “and would consider incrementally increasing the TBO after the engines had proven themselves in the field. Problem is that nobody is going to buy one of our certified engines if it has only a 1,000-hour TBO, so the engines will never get to prove themselves. It makes no sense, Mike. It’s not reasonable. Not logical. Doesn’t seem fair.”
 
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I regularly flew a rental 172 with 3,900 hours on it when I was in Arlington, WA. By that point it was getting close. The engine seemed fine, but oil usage was up and ended up being the thing that drove it into overhaul.

Jim
 
Engines start "sweating" (leaving oil residue on the engine from condesncing vapors and oil vapors coming out of places). The compressions start coming down. Engine doesnt quite make as much power as it used to. Its a gradual process.

You can fly quite a bit past TBO if you dont mind some of the above and your mechanic is ok with it and will sign it off. 3000 is common in new engines. Even more. But after a while, it has to be rebuilt. Reman and rebuilt engines wont last as long as new, on average.
 
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4300 hours just seems like a lot if the recommendation is 2000 hours. (Says a guy who skips recommended maintenance on his car all the time...) Just makes me nervous. Another vote for buying my own!

If Lycoming had motivation to increase TBO, they would. But they don't. If they did, I think 2,500-3,000 would be pretty easy to achieve.
 
TBO isn't a magic number.

For example, there was a news story recently (sorry, don't remember where) about a company that makes parts for Lycoming engines...basically they make approved replacements for every part of the engine.

They were looking at assembling their own engine. Using the Lycoming design and already approved parts, they were told they couldn't get a TBO of >1,200 hours on it...remember, same design, same parts, just over half the TBO.

EDIT: Found the article:
http://blog.aopa.org/opinionleaders/2014/05/13/tbo-free-engine/

Given the ECI cylinder AD I can understand the FAA wanting a few years of operation to prove their quality control process. That said, for 91 it really doesn't matter except from a marketing standpoint.
 
Given the ECI cylinder AD I can understand the FAA wanting a few years of operation to prove their quality control process. That said, for 91 it really doesn't matter except from a marketing standpoint.

Considering the small market, the marketing standpoint is the one that matters. Now if they wanted to develop the market, they could price them as 1000hr engines. (Given Pt.91) If I could get a new ECI engine with a 1000hr TBO for the same price as an overhaul, I may go for that, especially with a reasonable warranty. I'd be looking at making deals with flight schools that run a lot of hours so I could compile the data for TBO extension as quickly as possible. A busy school can rack them to 3000hrs in 2 years. You get a hundred or so out there holding up 5000 hrs and 5 years, you get your TBO extension.

Why should the consumer have to pay all the risk at full boat price?:dunno:
 
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