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Lycoming SB632 - bad conrod bearing assemblies

Lycoming did it again — ship bad parts from the factory and now make money on customers having to replace them with good parts. This one looks quite nasty.

http://www.lycoming.com/sites/default/files/SB632%20Connecting%20Rod%20Identification%20and%20Removal_0.pdf

As the failure mode is unpleasant, it could become an AD in my view.

It looks like all engines that had overhauls or conrod replacements done using parts deliverey by Lycoming between November 2015 and February 2017 are affected. The SB contains a table of engine serial numbers (probably those overhauled/shipped by Lycoming) and part numbers of the broken assemblies.

If you engine had work done between Nov 2015 and now, you should check this.

This could be a huge issue for all recently rebuilt Lyco engines and I agree it is likely to become an AD.

There is a warranty mentioned in the PDF but in most cases where someone had an engine done within say the past year the whole job will be at the engine shop’s expense, because a warranty to the end user is on the whole engine. Or the whole plane if you bought a new plane as an end user (not as a company).

Administrator
Shoreham EGKA, United Kingdom

I removed a few posts discussing a typo which was corrected

Administrator
Shoreham EGKA, United Kingdom

I hope your newly overhauled engine is not affected?

My US shop used Superior parts, so not affected.

This is going to be REALLY BIG. It’s going to be an AD and with the 10hr compliance deadline it is going to have a big effect.

One has to wonder how it was discovered.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

used Superior parts

@Peter, what do you call superior parts ?
Which one are they ?
Are there different brands ?
Did the shop supplied its own, or a “kit” of “superior parts” ?
Is it specific to your US Shop, or do some European shop are able to use such superior parts ?

This indeed will be big and an AD here soon. We have 12 C172s in our training fleet and 3 were affected. They are grounded until we can get the tool and start the inspection.
We did have a in flight event happen not too long ago because of these bad rods. The rod failed and punched out just over a 1/3 of the case on the left side. 100 hours after major overhaul too.
What we are worried about is how far does this go. How many engines will need new bushings & hardware and do they really have enough inventory to facilitate and timely response.

I would be suspicious of that test with that spring-loaded tool…

I incidentally phoned my engine shop yesterday and asked how this procedure can be done “most economically”. Apparently it is possible to do it with the engine in situ. You remove all the baffling. Each cylinder can be pulled off just enough to not reveal the piston rings (so the piston remains in the cylinder; this can be done even if the piston has to be disconnected from the conrod and crucially avoids the need for new rings + a re-hone + the whole running-in procedure, burning a load of avgas for half a year) and you can access the conrod small end bearing that way, changing the bushings completely if necessary. Any engine builder with a brain will know this but it’s worth writing down anyway…

I would not use that tool. Chuck out the Lyco bushings and put in the Superior ones. Still the cost will be thousands, with Lyco footing the bill within the terms of its warranty to the engine shop. The recovery of the labour costs at your end, extra hangarage, etc, is a separate matter. And a private owner has no claim for downtime because, hey, ho, there is no economic loss

The irony in all this is that those who say you should use original mfg parts only (and probably insist on them as the purest interpretation of EASA requirements, especially for AOC ops) are getting screwed, but those who use Superior PMA parts are OK. The SL parts are Superior

Administrator
Shoreham EGKA, United Kingdom

Peter, the procedure you describe is mentioned in detail in the SB with photos…

I’ve done some digging, it seems that the vast majority of field overhaul shops use Superior bushings. I don’t think there is any “use original manufacturer parts only” bias among overhaulers or this matter even reaches the customers. They use what is the cheapest to source and known to be good. Lycoming is neither of the two…

Last Edited by achimha at 19 Jul 06:38
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