Nasty Lycoming AD

[mAgNeToDrOp]

Could be expensive... Sounds like it should rather be done in an engine shop rather than your run of the mill maintenance workshop?

 

Lycoming AD

 

 

[IanR]

We had one of ours done last week. Luckily it passed so didn't have to have the rods removed.

 

 

[zodiacpilot]

Soooooooo, where is CASA requirement for a passenger signed form until the engine is pulled down ala Jabiru?

 

 

[Downunder]

A very interesting read, that article in the first post.

 

I'm wonder how a wrong physical dimension can pass QA these days in an aircraft engine? Perhaps poor metallurgy or heat treating, but the OD of the bush being undersized.....

 

 

[facthunter]

Anyone fitting them and not noticing shouldn't be allowed near an aircraft engine. "Boss, these bushes are too loose. They press in too easy".. Nev

 

 

[Yenn]

The first I heard about this was a Savvy Aviator post by Mike Busch. He was explaining that the FAA was mandating that all possibly affected engines should be checked. His fear was that more failures would be caused by the checking, than by an actual failure of the component. I am not sure where it stands at the moment and I have not read the fine print from CASA as My engine was built before the components were made and it is not on the list.

 

It does seem stupid to do major surgery to fix a possible fault in less than ideal conditions. we all know that the immediate post maintenance period is a time of possible problems.

 

 

[jetjr]

Reading somwhere the failure rate in effected bushes is quite high, like 1 in 5 fail test

 

Serious end results so a significant and urgent SB

 

For interest what would this inspection cost?

 

 

[facthunter]

Depends on how many rods need replacing and you would have to balance match them. . Like I said earlier. Why wouldn't the person pressing them in, notice they didn't have the right interference fit. Id be asking MY mechanic why they didn't notice when the motor was built. Once they notice there's a problem they would be pretty liable if they didn't recommend a fix. You'd probably put rings in and a light hone to the bores to make them bed in. Wouldn't end up being cheap. Coupla grand if you're lucky. Nev

 

 

[jetjr]

I know little of these engines however it was also discussed IF there was found to be out of spec rod/ bush, it was recommended factory exchange units used as there was some skill needed to insert.

 

They are present even in new factory built engines

 

If true, its even more of a worry as to why it wasnt picked up

 

 

[facthunter]

You are right.. There is some skill to press things in straight , and it is perhaps best to do it at the factory or they should run them direct in the rod and chuck it when it gets out of tolerance. As this instance shows, a bush is something else to go wrong. Nev

 

 

[IanR]

Reading somwhere the failure rate in effected bushes is quite high, like 1 in 5 fail testSerious end results so a significant and urgent SB

For interest what would this inspection cost?

Lycoming quotes about 13 hours for the inspection if nothing is wrong plus you have to buy the test tool.

 

 

[ozbear]

Anyone fitting them and not noticing shouldn't be allowed near an aircraft engine. "Boss, these bushes are too loose. They press in too easy".. Nev

Being an aircraft engine as in all interference fits od of bush and ID of rod should have been checked and known

 

 

[aro]

Anyone fitting them and not noticing shouldn't be allowed near an aircraft engine.

Are they inserted by the engine assembler? I assumed they were inserted during conrod manufacture and supplied as a finished conrod assembly to the engine builders.

 

 

[facthunter]

However they are done originally, repair would not always be "in house." Supplied or originally fitted the dimensional error is the problem. Period involved is known so a limit to applicability of AD.. The "interference' fit required, is not maintained. So they are coming loose in service, and causing failures. They might decide to have exchange conrods or whatever (just replace with new). They couldn't prevent others doing the work if the outcome is OK . things like this and cast rocker failures in some later Continentals should not be happening. Quality control arrangements must be inadequate... Is the only conclusion. These are good brand name products. Piston engine reliability is not easy to maintain but it can be done. No engine is guaranteed to just keep running, especially pistons. Nev

 

 

[Yenn]

Why would you need to put in new rings or re hone the bores? This inspection and renewal could be done without removing the piston from the cylinder.

 

 

[IanR]

Why would you need to put in new rings or re hone the bores? This inspection and renewal could be done without removing the piston from the cylinder.

Correct - that is how its documented - slide piston down just enough to remove gudgeon and leave piston in the bore

 

 

[facthunter]

I'll put it to you another way. If the barrels are already off, why not? if the motor has done some hours, it's worth freshening it up. Less blowby means a cleaner running motor. and why wouldn't you decoke it at the same time?. It depends on the condition it's in. Ring gaps, tension etc. Unless the motor was low hours from a top or rebuild and all compressions right up it would be a bit silly to not use the opportunity to check.. Cowls and everything are off. Cylinders on a bench. Nev

 

 

[IanR]

I'll put it to you another way. If the barrels are already off, why not? if the motor has done some hours, it's worth freshening it up. Less blowby means a cleaner running motor. and why wouldn't you decoke it at the same time?. It depends on the condition it's in. Ring gaps, tension etc. Unless the motor was low hours from a top or rebuild and all compressions right up it would be a bit silly to not use the opportunity to check.. Cowls and everything are off. Cylinders on a bench. Nev

Nev, unfortunately most of the effected engines have very low hours - ours only 130 since overhaul !!

BTW are you going to Nuriootpa in September ? Would be good to catch up

 

 

[facthunter]

I covered that , I hope in the possibilities. No I'm not going Ian. There's a large number entered so you won't be lonely. Give my regards to our friends in common and have a good time. Beware of the "corkage " charge. Nev

 

 

[dave_mccurdy]

Anyone fitting them and not noticing shouldn't be allowed near an aircraft engine. "Boss, these bushes are too loose. They press in too easy".. NeIf the installer has evidence of measuring the bushings adn finding them to be in tolerance then would you still be reguired to pull them and check them?

[facthunter]

Dave, If any kind of commonsense prevails one would hope so. They specify their own testing gadget that only applies a load (I presume). If the measuring was done and found within tolerance on sizes, then the required interference fit's are there. How can anything better be achieved? Nev

 

 

[derekliston]

Question which may at first seem unrelated. In the last year I have received three recall notices for my Mitsubishi Pajero, in each case costs are covered by Mitsubishi. Now, if the Lycoming problem is of the engine manufacturers making, shouldn't they and not the aeroplane/engine owner be liable for the cost of inspection/repair?

 

 

[Downunder]

Question which may at first seem unrelated. In the last year I have received three recall notices for my Mitsubishi Pajero, in each case costs are covered by Mitsubishi. Now, if the Lycoming problem is of the engine manufacturers making, shouldn't they and not the aeroplane/engine owner be liable for the cost of inspection/repair?

It does seem to be an odd thing about aviation where owners are expected to pay for manufacturers defects.

 

I have had to purchase products for engine and aircraft safety/service bulletins.