Engine talk

[Dan]

I have seen several adds and spoke to someone yesterday whos engine, in this case an M20C, had top end overhaul recently, but had 2300 hours since total overhaul. Two things came out of this conversation.

1) The owner was not an A&P but had done the engine work  Isnt this agasint some FAA rules?

2) I wonder about engines that have not been overhauled but have had the top end done. Does this mean you can push past TBO safely?  Is this just kind of a band aid for an engine that has compression issues and is patched until TBO? or ???

Thanks.

Dan

[Cruiser]

1. The owner can do the work under the supervision of an A&P. Look for the appropriate entries in the engine log book.

2. Top end parts can wear more than the bottom end and will sometimes need replacement when (in all probability) the bottom end is still good. Any decisions on engine life beyond TBO include the engine performance and (in my opinion) several oil analysis that show trends over time. Many engines run hundreds of hours beyond TBO without incident.

[Dan]

Thanks for the info. I got the feeling that an A&P was not involved as I asked if he was an A&P and he said no he used to work on aircraft in the service. So if the logs dont have the proper endorsements, I assume that would then be agasint whatever laws?

Dan

[KSMooniac]

You are correct, Dan.  If the non-A&P owner did the work and there is no supporting log entry with an A&P signature, then he broke the rules.  Even if he did good work, I would still run away from that plane b/c he has demonstrated a bad attitude with regard to maintenance and following the rules, and there is no telling what else has been done without documentation.  He could have done some other work on the airframe that a savvy A&P/IA might find as an un-airworthy item that could cost a lot to undo and/or fix correctly down the road.

This spring I had to do cylinder work on my 1650 SMOH engine.  I did the vast majority of the work, under supervision, to remove & reinstall the cylinders.  A local shop put in new valve guides and seats, honed the cylinders, and gave me new pistons/rings/pins.  I had low compression on 2 cylinders and opted to go this route (not a full TOH) and that *should* get me many hundreds of hours down the road.  My cam and crank looked good, and oil analysis had been good prior to this work, so I plan to keep running past 2000 SMOH as long as everything continues to check out and perform well. 

All that aside, I would not buy an airplane with an engine past 2000 SMOH and expect it to continue running since I wouldn't know how it was treated.  If such a plane is a candidate, price it as a complete runout and be prepared to OH at any time, and if you keep flying it, just consider those hours as a bonus.

[MooneyMitch]

Dan,

Search Google  "TBO Mike Busch AVWEB".  Read his opinions on TBO.  Many others support Mike's theory as well.    You've got to know the engine history and it has to be supported by positive/thorough documentation. 

[philipneeper]

im kinda in the same boat.. the engine now has 2400 since tbo.. i was thinking if the case and crank are good to hook just do a top end to be safe... i will be doing the work myself under the supervision of an A&P. what are your thoughts? mean while i will google the above posting

 

[DaV8or]

If it were me buying this plane (and I have been shopping, trust me) I would consider this plane to have dead motor and negotiate/budget for a new engine on day one. I would also have this plane looked over thouroughly by a MSC like Top Gun in Stockton. Somebody with solid knowledge really needs to check on the questionable maintenance. The engine in the plane now I would personally use just to ferry it to the engine shop, but that's me. Lots of other folks like to take chances with engines just to save a buck.

[danb35]

Quote: DaV8or

Lots of other folks like to take chances with engines just to save a buck.

[scottfromiowa]

Walk away or get price as if engine is run out.  I made wrong decision.  Don't repeat my mistake.  Buy it right or walk.  That said I TOTALLY AGREE with danb35's comments.

[DaV8or]

So as to not create a lot of thread creep, IMO, I would consider the engine in question to be worn out if I were buying this plane. The owner may have all kinds of receipts and log book entries, but I would error on the side of caution here. There is too much money and personal risk at stake. I would not be swayed by brand new cylinders and pistons.

Thankfully, the FAA allows us to be Americans and make choices as we traditionally always have. Individually. Lycoming has decided that 2000 hours is an average time at which an engine is close to failure. Some will blow up sooner and others will go on and on. Where your engine falls on the bell curve, nobody knows for sure until it comes apart. The awsome thing is, we get to choose. This is what makes our country great. If you believe you have a system and are smarter than the average bear, go for it!

For the prospective buyer, I feel you have nowhere near enough certified data to make an educated guess on how much further an engine will go. I would side with Lycoming in this one.

[Barry]

I had a 1949 Piper Clipper that had 2,450 hours on the O-235 C-1 and was still running GREAT! I had to rebuild that engine, despite it ran well with that high time, because I could not find a mechanic who would sign-off on the engine during my annual. I suspect you will have the same problem.

[RJBrown]

I own an  auto repair shop. What I see in engines depends on how a customer treats and maintains the vehicle. Identical cars can be junk at 100,000 miles or still running strong at 300,000. Most "lemons" are a result of customer abuse. With the ability to control  all the parameters of the engine such as mixture, cowl flaps, RPM, etc. we also have the ability to abuse our engines in ways a car operator can't. How long our engines last depends on us more than anything else.

 TBO is just a manufacturers recommendation, for part 91 it has no regulatory significance. We are free to run our engines as long as we feel comfortable doing so. The 4 cylinder Lycomings historically have shown the ability to run safely past TBO. For me to feel safe  an engine near or past TBO should be on an oil analysis program and have solid maintenance records. 

 Any engine past TBO that is in a plane that is for sale I would consider worthless as anything but a core.

[carusoam]

Stuff to consider....

[1] An average M20C flies at 150mph. - pretty quick...

[2] At 2,000 hours, that engine has dragged the plane 300,000 miles.  - pretty far...

How far do we expect it to go......?

What will fail first....?  (crank, cam, seals, block, etc.)

What accessories can we do without?  (fuel pump, carburetor, govenor, magnetos, cylinder assemblies, etc.)

Can we start a meaningful oil analysis program now?

There are many things that can get old and worn....

If you replace all the questionable items, one item at a time, you probably have replaced all of the items required for an overhaul.

I might be with RJB on this one ...

The core is usually a valuable commodity for a rebuild.  (slightly more positive than "worthless")

-a-