Factors that affect Engine Life

[dcabrown]

Hi All, I did a search throughout the maintenance forums and couldnt find this topic..

I'm a hopefully soon-to-be first time owner in the market for a Cherokee 140 or 151 and keep seeing a lot of aircraft with 1400-2000 HR engines with 70's compressions.

I understand there are no requirements in Canada to overhaul at TBO and there is no time limit as well...

My question is, what are the general factors that will allow an engine to make or exceed TBO. For instance, will wet/damp environments (B.C.) cause more corrosion? Why do some cylinder have to be pulled after a few hundred hours, whereas some can go 2000? Quality of overhaul shop? What kind of additional tests (beyond compressions) should you look at when buying a higher time engine (i think ive heard a bore scope test (?) of something like that is a good idea to detect engine wear?).

All in all, is there a general way prospective buyers can assess whether an engine will have another 100 hrs life on it or an extra 1000hrs?? I'm really worried that if I buy an airframe with a 1400 hr engine, it will require overhaul in a few years. Then again, I've heard of some ppl who have pulled their engines at 2500hrs, and the mechanic says it could have gone another 500hrs no problem... how do you find those?

2 other questions...What is the big issue with engines that may not have a lot of time on them, have good compressions, but have not been overhauled for 25-30years?
Also, which overhaul shops in Canada have a solid reputation?

I know ive just listed off tonnes of questions, so i thank you in advance for any help you may be able to offer in even answering just one of those questions.

Darryl

[Cat Driver]

Jesuses dcabrown that is as difficult a question as telling us you are getting married and asking us what you should look for performance and reliability wise in your prospective wife.

So here are a few tests.

Suction..

Compression.

Wet sump, dry sump.

Listen close to how it sounds.

Those are a few things I can suggest.

[tiggermoth]

Well, here is a few quick tips I have:

-Check the oil and oil filters for metal contamination every oil change. A few tiny specks is normall, lots is bad.
-You mentioned compression checks, do these regularily!!!
-Yes, wetter climates (Vancouver) will corrode stuff faster. This goes for the whole aircraft, not just the engine.
-Running the engine regularily is better than letting it sit. ***NOTE: By running it regularily, I do not mean for 5-10 minutes on the ground to "circulate" the oil. I mean go out and fly for an hour. This is the only way to get it hot enough for long enough to "burn off" any moisture in the engine. Just running it on the ground for a few minutes will warm up the engine just enough for even more condensation to form after shutdown, thus compounding the problem.

The best way to get a good evaluation of a prospective engine is to get an AME with experience on the type of aircraft/engine to give it a good look over. A low time engine but has been sitting for a lot of years may still be in good shape IF it was pickled (preservation oil) properly. Again, this is something for the AME to check out.

As far as overhaul shops, a couple that come to mind out west here are, Alberta Aero engine in Edmonton, Progressive Air in Kamloops, and Okanagan Aero Engine in Kelowna.

Other than this, like Cat said, it is very difficult to tell just what you can expect out of an engine. I have seen a couple with low to mid times, good compressions, and no metal in the filters and oil suddenly just go kerboom, and quit. Others, like my continental o-300 in my C172, has over 1600hrs, compressions in the low 70's, only has the original oil screen, and it purrs like a kitten and probably will for some time yet. The best you can do is regular oil changes, compression checks, and fly the airplane.

Tigger

[cgzro]

Assuming the engine has been put together properly, which is more than likely the case I suspect that the main problem most GA owners have is simple lack of use. A very light dusting of rust forms very quickly (week or so) and causes serious problems.

Lycomings are well known for their camshaft and lifter problems that occur if the cam/lifters are not subject to lubing up every few days by running the engine. I believe Lycoming says that even 2 weeks without use requires long term storage. .. how many folks actually bother to preserve their engines with 2F during the winter?

As a result, if I were purchasing and older, lightly used but otherwise good appearing Lycoming, I'd probably insist on pulling the #1 cylinder so that I could look at the sate of the lifters and camshaft faces. .. wish I'd done that when I bought mine, would have saved $30K... live and learn. If the owner does not consent to it .. well move on .. its too risky.

Anyway when the camshaft/lifters start to go you will get little flat slivers of iron (metalic) in the screens, not much at first .. then a bit more and eventually the iron will go from a mostly 2 dimension shape to having a bit of a thickness .. thats when its comming from the sides of the lifters and now you are in dangerous territory. Anyway all those little flakes will fall down on the cylinder skirts and ride back and forth on the cylinder walls scratching them .. so you will then start to get oil fouling and a look through the plug holes will show scratches of course.

Expensive stuff that can be avoided by flying the heck out of the plane and preserving the engine if its offline for more than a few weeks.

[pilotincommand]

also keep in mind. a engine with high time will have a heavier insurance bill then one with lower time. Thats just something i have noticed over the years with my bill. Also the more hours you personally put on the airplane the cheaper the insurance will be. so really one evens out the other. so like said above.... fly the sh*t out of it, and have fun


PIC

[MUSKEG]

Go for a ride with the owner and observe how he handles the engine. Especially approaching and in the pattern. That should send you in one of two directions. 1) To a good A/C engineer or, 2) to run as fast and as far as possible.

[Hedley]

TBO is meaningless to a private operator, both practically and legally.

I have flown an engine with 5500 SMOH. They just kept changing jugs and accessories. It was never cold started, and never sat unused to corrode.

As Peter points out, the weak link of a Lycoming is that frigging camshaft. You park a Lycoming without pickling for a year or so, you have to split it to change the cam, which is a major overhaul.

Best thing you can do for a Lycoming is fly it every week. The journey log will tell you if you have a problem looming or not.

Don't buy a Lycoming without looking at the pressure screen, and cutting open the oil filter.

If it's making metal, you've got a major overhaul to pay for, regardless of hours since the last major overhaul.

[niss]

viewtopic.php?t=28813

Give this a look over.


I have nothing to say other than what has been covered. My only other recommendation is to sacrifice a dove and sprinkle it's blood on the cowling to appease the aviation gods.

Sometimes it comes down to whether you are in their good graces or not.

[Brantford Beech Boy]

Jesuses dcabrown that is as difficult a question as telling us you are getting married and asking us what you should look for performance and reliability wise in your prospective wife.

So here are a few tests.

Suction..

Compression.

Wet sump, dry sump.

Listen close to how it sounds.

Those are a few things I can suggest.

Hey Cat,
are those things to look for in an engine or a wife?

BBB

[Cat Driver]

Both.

[canwhitewolf]

maybe worthwhile investigating this, approved by the FAA

Lenckite or avblend

http://www.avblend.com/faa/kas_thomas_lenckite.html


sean tucker and his incident

http://www.zmax.com/documents/avblend_f ... _story.pdf

http://www.zmax.com/why_use_zmax_/testimonials/