TBO O-320 150 HP

[eskflyer]

My engine is at 2100 now , compression is no lower than 76 high is 78 , not making any metal all normal oil analysis. No oil consumption to speak of she leaks more than she burns. In your guys opinions would you keep flying it or do a major. the ole girl is flown weekly for a average of 8 hours. I have some people telling me that the O-320 will start to destruct at tbo and others say run her until she shows problems. Oil analysis is done every 50 hours .

Thanks
John

[JohnW]

Run it, if you are so inclined. For "Part 91 airplanes", overhauling the engine at recommended TBO is not required "by Law". In other words...the engine is "on condition". Now, whether or not it is PRUDENT to "run it 'till it drops" is a whole 'nother matter. Generally speaking, splitting the cases and going through these very expensive parts is in the best interest of whomever owns it when it fianlly "craps out". Yet it's cheaper to overhaul than it is to "purchase a replacement core and THEN overhaul it... Not that there isn't "a middle ground"!

Some people consider that they can "never own an airplane, only be the caregiver for it". Running it until it drops is the MOST EXPENSIVE way to operate an engine, if it "drops" when you own it (not that I recommend that you fly it until it gets lame and then sell it to somebody...I think that's criminal). But it's a "personal choice". Why...some people even feel it's "okay" to be a "selfish lover". But there sure ain't no long-term future in THAT, either.

The engine manufacturer has a pretty good handle on how long one of their "reasonably maintained" engines will maintain "serviceability" under average use. Your choice (after considering how this particular engine's "use" could be said to "stack up" against the word "average"), but consider whether you know ALL the history of this engine since the last time it was overhauled (or new). "Short hops", contrary to what you might THINK, are not "the best way to treat your engine" simply based on the relatively short number of HOURS accumulated. "Cycles" speaks more about longevity than "hours", and as far as "wear and tear from normal use" is concerned, why...starting your engine, running it until it is at "normal operating temp" and shutting it down" is for all purposes the same whether you "cruise it" for five hours steady, or circle the airport twice and landing. Engines that do EXACTLY THAT (go 'round and land, go 'round and land...) -TRAINERS- invariably virtually NEVER make TBO. Whassat tell ya?

[mjlossner]

John I'd really like to meet you some day, I Like your attitude!!!
My two cents worth on the subject on TBO, I worked for a FBO that operated 3 172's and a Warrior all with O-320's. The Owner felt that if 2000 hrs was good 3000 was better. Welllllll... two of the 172's went to 2800 and some change and started making metal found at the oil change. The Warrior quit on roll out and caught fire trying to restart it around 2200 hrs and they decided to exchange the last 172 at 2500 hr. Lycoming has that recommended 12 yr. thing on there engines too. My Opinion (and thats all it is) is that after 2000 hr your living on borrowed time, pay me now for that Overhaul/Exchange or pay me later for that engine without a Core due to a Bad crankshaft or worse. I haul my Grandkids in ours and the last thing I wan't to tell there parents is that Grandpa and the Kids are in a Field somewere and need a ride home.
Love all the input, keep it coming, Mike..............

[Steve Pierce]

Sounds like to me you fly it regularly and monitor the trends. If something starts going south you will know it. Most of the problems I have seen with Lycoming engines has been from inactivity. You fly it regularly and treat it right which is a big plus over a flight school airplane. Cam and lifters will give you way advanced notice with steel in the filter/screen. Oil analysis, compression, consumption and filter/screen inspections will tell you their condition. I have been using a borescope and have been able to tell why that cylinder is a little low and wish I had bought one years ago. I ran my O-235-C1 in my Clipper to 2600hrs/2400 TBO. It had been top overhauled and always had good compression. I swapped it out for a mid-timed engine when the oil consumption went from a quart every 3 hours, which it did from the day i bought it and is acceptable according to Lycoming, to a quart every 2 1/2 hours. I tore it down and the only thing wrong was that the rings were worn out. Used to do some maintenance on some pipe line patrol airplanes. They ran 100 hrs a month, every month, 100 hours between oil changes and had some with over 3000 hours. However I don't think they kept as close of an eye on things as it sounds like you are doing.

[d.grimm]

The flight school I worked for had Warriors and C-172's that flew a hundred hours a month. Every overhaul was everything rebuilt firewall forward with new cylinders. Our engine shop (Lycon, Pontiac, MI) asked why we were overhauling so soon.
We eventually went to 2400 hrs, and I can't ever remember removing a cylinder before overhaul. Not all flight schools are created equal.
Dave

[Lownslow]

The O-320 is a very dependable engine and will usually make TBO+ under the proper care and operating conditions, also depending on the quality of the last overhaul. I will offer that any engine with "high time" be looked at closely and frequently to detect any signs of iminent failure. Oil filter/screens inspections is good, but checking for any other usual leaks or noises is extremely important and should demand immediate attention, ie frequent compression checks, any noticeable mag drop or rough engine, oil leaks and exhaust leaks, a knock or a "tick". The most common high time engine mode of failure (from my experience) will be some type of cylinder failure, whether found during inspection or noticed under operation. Losing a cylinder on a 4-banger in flight is no minor event and cause severe upholstery wedgies. I have witnessed cylinders after injesting a intake or exhaust valve, leaving the engine with <75% power, and shaking like a prostitute in church. I have known experienced pilots to panic and lose control of the airplane under such an event, even in a most-favorable scenario situation, and not walk away from it. Oil leaks should not be accepted as norm. I've seen oil leaks from cracked cylinder heads and pulled threads on thru-bolts (not on O-320's). Operating past TBO should a jugement decison on an individual basis (with consultation and guidance from a reputable mechanic), taking the proper precautions, and preparing oneself for the potential modes of failure. That's my $.02.

Lou S.

[Bultaco Jim]

Sounds like you're on top of it, so keep running it. Like Steve said, inactivity is bad for it, but constant use is just as good for it. The flight school at my field always got over 3000 hrs. Checking your oil will give you plenty of warning.

[Lownslow]

Of course what some choose to do, when either indications of a cylinder problems start to appear or to provide "insurance" to a judgement to delay complete overhaul (and save $) is to do a "top" overhaul. A "top overhaul" will bring the cylinder and outer valve train components to a relatively new serviceable condition when a judgement is made that the internal components are likely to be serviceable for an extended period of time, based on known operating conditions and operating practices. This is another way commonly used to extend operation past TBO for part 91 operation. This practice was and is likely still common for many of the Continental engines that would have cylinder problems after a few hundred hours and well ahead of TBO. But they are getting better with some of the new materials and processes ( Just adding another $.01).

Lou S.