12 year MOH recommendation

[jmvolpp]

Would the tribe's engine experts care to weigh in on the 12 year engine overhaul recommendation as per the latest TC newsletter? Surely some of us are running low (hour) time engines past that decree.

Mike V.

[flyguy]

Re: 12 year MOH recommendation

Pick a number. What great god of maintenance delivered that number down from his throne in powerplant heaven? Why 12? Do a lot of engines fail after 12 years regardless of runtime or good or poor maintenance?

Sorry don't mean to be a smart a**, but what is the basis for such ideas?

Darryl

[GLB]

Re: 12 year MOH recommendation

Flyguy asked what great god of maintenance delivered that? How about TC liability lawyers with at statement they're thinking their off the hook for liability, after all your not following their maintenance rules.

[3Dreaming]

Re: 12 year MOH recommendation

I think the 12 year mark comes from gaskets, seals, and sealant breakdown. There may not be anything wrong with the metal parts, but these parts have life limits that could lead to an engine failure. Tom

[Larry Lyons]

Re: 12 year MOH recommendation

Well mine has been over 33 years and not a sputter yet. Of course is has not run in that time either!!!
Larry

[Hank Jarrett]

Re: 12 year MOH recommendation

My first thought was that it was connected with the General Aviation Revitalization Act (GARA) of 1994 to limit product liability exposure for manufacturers, but THAT was an 18 year limit.
Different materials last different times (shelf life and operational life) and the life of any seals and gaskets are changed by the type of use. One overheat can mess up a lot of seals where regular use (with no abuse) and they could last for decades. I can't imagine where the 12 year limit comes from.
If there is no basis (life limit) for something like this, it should be a conditional inspection requirement, NOT an arbitrary overhaul requirement based on age.
I really don't read it as a mandatory overhaul, but a recommended, like the TBO. Am I reading it wrong, or do we have some overly conservative IAs and A&Ps. I'm ALL FOR being conservative, but I have sure seen a lot of REALLY OLD engines that ran great for decades.
Hank

[astjp2]

Re: 12 year MOH recommendation

It does not apply to part 91 operators or people operating under the light sport rule, but it does apply to part 121 and 135 operators. Lets not over think this one....Tim

[Hank Jarrett]

Re: 12 year MOH recommendation

I plan to go to my trusted IA. If he says the engine is good, that's good enough for me. If he says tear it down, well, he always takes the first flight after an annual. We will tear it down. It all comes down to trusting your professional. He has never taken me down the wrong path yet, whatever the FAA says. I trust my mechanic with my life, like we all do.
Hank

[Len Petterson]

Re: 12 year MOH recommendation

Im Canada we have a 10 year internal corrosion and general condition inspection rule.
We did remove cylinders and ground valves on my new "used engine" under this rule.
Len

[3Dreaming]

Re: 12 year MOH recommendation

It does not apply to part 91 operators or people operating under the light sport rule, but it does apply to part 121 and 135 operators. Lets not over think this one....Tim

Airplanes operating as a special light sport may have to follow these guidelines. It all depends on how the maintenance manual for the airplane is written. If the mannual says follow manufactures recomendations then it must be done. The operating limitations attached to the airworthiness certificate state that the airplne must be maintained in accordance with the manufactures recomendations. For example the Rotax 912ULS has a 100 hour inspection that has to be done regaurdless if the airplane is operated privately or commercially.

The thing to remember is our old airplanes get maintained the same as they always have the rules did not change for the airplane, only the pilot.

[wlas]

Re: 12 year MOH recommendation

One of the reasons for this with part 135 is for rust from setting long periods of time. The cams rust and after they run again it wears out the cam. I forget how many Lycomings I've found this on. One of the differences with Lycoming is the cam is on the top of the case and water collects on the cam. Although I run across it with the bigger continentals like 0470s and 0520s. I run across big blanks in the log books all the time or only 1 or 2 hours in a year. Condensation is the big problem, when an engine doesn't get used.