Run beyond TBO (AKA, I really want this plane)

[Joe B]

1969 Beech Musketeer. TT 6071, 2110 SMOH, 820 STOH.

it is not that far along since Top Overhaul, the engine is not making any metal and the engine compressions are good and healthy. Last compression check showed: 1-74/80, 2-78/80, 3-70/80, 4-71/80.

Top overhaul halfway to TBO usually means the engine is being run hot and hard. You have to assume that practice continues. The new cylinders are probably about 80% used up now - anything beyond another 100 or 200 hours is a gift. (Edit: Could be old ones were simply TCM cylinders. If that's the case and current ones are ECI or Superior, you might have some good cylinders there. Hard to tell - assume the worst.)

Annual due 02/08

Irrelevant. You've no idea if it was a good annual or if it was pencil-whipped. You don't want to wait until next Feb. to find out it was pencil-whipped and the aircraft is full of problems which are now all yours. Ideally, you'd like to have your IA do a prebuy and, if that's satisfactory, keep going to complete an annual. You pay for the inspection, seller pays for any airworthiness issues. Do not use the same guy as just completed the annual.

Aircraft is currently flying and flys often.

That's good.

Regards,
Joe

 

[Bill]

IIRC an overhaul is about $15K.

I'd think an o-360 overhaul is going to run you at least $20k.

 

[Bill]

IO360 engine rebuilds: I have mine out for a major right now. Quotes from 4 major shops ranged between $17,400 and $21,500 with overhauled Cermanil jugs. New cylinders ran $21,700 to $23,300 at the same shops.

Oh -- and add in a contigency for the inevitable "guess what we found" phone call from the shop.

Right! Anyone who thinks they're going to overhaul for $15k is smoking some good...uh.....stuff.

 

[waldo]

Right! Anyone who thinks they're going to overhaul for $15k is smoking some good...uh.....stuff.

You can perform a back-yard overhaul, with new cylinders, for that price if the cam and crank are re-usable and you do not replace accessories (not required).

 

[Tom-D]

Right! Anyone who thinks they're going to overhaul for $15k is smoking some good...uh.....stuff.

You need to talk to your local A&P, disassembly,inspection, cleaning, shipping, new parts, and a fixed rate labor for reassembly should cost WAY less than that.

 

[SCCutler]

You need to talk to your local A&P, disassembly,inspection, cleaning, shipping, new parts, and a fixed rate labor for reassembly should cost WAY less than that.

Yabut, Tom-

Don't you know that the only overhaul worth doing has to be done in a large factory with huge stock rooms and machine shops and file servers and stuff? If the place is not big enough to have a loading dock and a forklift, no-way no-how you gonna get a good engine out of it!

 

[Tom-D]

You can perform a back-yard overhaul, with new cylinders, for that price if the cam and crank are re-usable and you do not replace accessories (not required).

I wouldn't call it a back yard overhaul, because if it is completed IAW the manufacturers overhaul manual, using certified parts, and repairstation rebuilt parts, it will be the same as any engine shops, quality is in the hands of the person reassembling the engine.

There is no magic in rebuilding engines, and there is nothing any engine shop can do to improve engine build quality, that any A&P can't do. Engine shops get very proficient at building engines, thus they can do it quicker, but not better.

 

[waldo]

I wouldn't call it a back yard overhaul

I agree 100%, I did use the term loosely I have rebuilt two engines with my mechanic (O-200 & O-360) and I trust them more than I would a factory new engine. Some folks just don't understand how simple an aircraft engine is designed. A Briggs and Stratton lawn mower engine has almost as many moving parts.

 

[Steve]

So simple a caveman can do it...

I
... Some folks just don't understand how simple an aircraft engine is designed. A Briggs and Stratton lawn mower engine has almost as many moving parts.

 

[Bill]

A Briggs and Stratton lawn mower engine has almost as many moving parts.

Yes, but lawn mower jugs don't cost thousands...

(Hey Spike, I said jugs, uhhh,huh,huh,huh,huh)

 

[Bill]

Don't you know that the only overhaul worth doing has to be done in a large factory with huge stock rooms and machine shops and file servers and stuff? If the place is not big enough to have a loading dock and a forklift, no-way no-how you gonna get a good engine out of it!

Interestiingly, the mooney we have under contract is being field overhauled by a local mechanic, no big name shop. New crank, all parts to new limits.

But still, most folks roll their eyes when I tell them it's a field overhaul. At a recent Mooney gather, all of the guys expected one to have a big name shop engine in their plane.

 

[NC Pilot]

But still, most folks roll their eyes when I tell them it's a field overhaul. At a recent Mooney gather, all of the guys expected one to have a big name shop engine in their plane.

An aircraft engine (like we have in our planes) is really a simple thing and any competent mechanic should be able to overhaul it, but there is still a paradigm that only a big name shop can do a competent overhaul. As long as you plan on keeping the plane for a while it is not an issue, but if you try to sell it early in the life of the engine you may get gigged on the price no matter how good the rebuild is.

 

[gismo]

An aircraft engine (like we have in our planes) is really a simple thing and any competent mechanic should be able to overhaul it, but there is still a paradigm that only a big name shop can do a competent overhaul. As long as you plan on keeping the plane for a while it is not an issue, but if you try to sell it early in the life of the engine you may get gigged on the price no matter how good the rebuild is.

The only technical issue I have with a local overhaul is the typical lack of a good test cell. That means making all the initial adjustments and checks after mounting the engine on the airplane where such checks and adjustments are a bit more difficult (but not impossible).

The other issue is the perceived value impact, but if you plan to keep the plane until you use up the "new" engine, that shouldn't matter much if at all.

 

[Tom-D]

The only technical issue I have with a local overhaul is the typical lack of a good test cell. That means making all the initial adjustments and checks after mounting the engine on the airplane where such checks and adjustments are a bit more difficult (but not impossible).

The other issue is the perceived value impact, but if you plan to keep the plane until you use up the "new" engine, that shouldn't matter much if at all.

There are service bulletins out for both Cont. And Lyc. to do the test run on the aircraft, do it right and you should have no problems.

I have flown engines I've overhauled right after assembly. point 3 ground run for leaks, and fly it.

 

[The rogue]

I have flown an airplane in AK that was field overhauled to "factory specs" new cranks, cams, jugs (heheheheheh...) etc. The engine was great, mechanically when it was overhauled.

For some reason, the chief pilot didn't like to preheat engines because it "wasn't cold" at -20F or -30F. "Yes folks, today it's going to be a balmy -20, no need to wear hats, gloves, or boots. Just go right out and crank that 206 until it dies. If the battery won't start it today, then tomorrow give her another crankin' until the battery dies! Someday she'll turn over and run!!") True story, I sat in my kitchen and watched it happen on both days!

Okay, I guess my point is that sometimes TBO doesn't make any difference if the engine has been abused. If the airplane had a known history, I would fly it past TBO. I think that I have done this on occasion with a few rentals. It didn't bother me then, probably because I didn't know any better. I still don't know any better.... I second the motion that a past TBO mill is better than a fresh overhaul right before the sale type of a deal.

--Matt

 

[gismo]

There are service bulletins out for both Cont. And Lyc. to do the test run on the aircraft, do it right and you should have no problems.

Like I said, it's not impossible and I suspect your methods are more than adequate, but not everyone who performs a field overhaul does a proper first run checkout per the SBs from what I've seen.