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  #21  
Old 03-03-2019, 12:23 PM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
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Location: Hinckley, Ohio
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I was going to sit on the sidelines, but here goes…

I don’t think any fingers need pointing. Most 912 operators (me included) are enjoying very good service life with very little maintenance. I have 400TT on my 12 with no gearbox problems. Very little metal fillings on the gearbox magnetic plug. If any metal fillings, I would attribute to the surface finish from the hobbing process when gears are manufactured. Virtually no oil consumption in 75-hour oil change. In my opinion the 912 is a perfect match for this airframe.

How many Lycoming’s make it to TBO? A quick look at sales ads for used aircraft show an awful lot of MOH before 1000TT. Cam/lifter spalling among other known problems.
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PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
RV-12 Bought Flying Oct 2015 with 48TT - Hobbs now 475

LSRM-A Certificate 2016
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  #22  
Old 03-03-2019, 01:22 PM
Dave12 Dave12 is offline
 
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Vladimir has almost 5000 hours on his o320 still runs great. Truth of the matter is Lycoming 4 and 6 cylinder engines very routinely exceed tbo.
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  #23  
Old 03-03-2019, 04:44 PM
AirHound AirHound is offline
 
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Location: OFallon IL now, everywhere before
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Quote:
Originally Posted by NinerBikes View Post
And yet galling still occurs in the gearbox, with metal on metal contact, with use of the specified oil, well before 2000 hours, in plenty of observed cases.

Should we point the finger at operator error?

Design failure?

Vendor failure for materials used and specified on the part?

Or oil failure? Rotax spec'd the oil... and gearboxes are failing, early.

Rotax has Qualitiy Control over all specifications except the end user, and operator error. Just like their Carb floats. Which they say is fine with Mogas up to E10, and they still keep failing. They've got a new part number out for the carb floats. Makes me wonder if it will ever happen for motor oil, too.

I'd love to see a failure analysis report as to the cause, because once that oil boundary layer is gone between the gearbox parts, the damage starts getting done. And there are fundamental differences in additive packages for motor oils, and in gear oils.

As to my Qualifications, let's just say I worked for the manufacturer of a bottle brush hone company that puts the final sealing finish on every single kind of sealing bore that you can imagine, both in the new and remanufactured engine industry. I've seen plenty of failures of surfaces that need lubrication, the metal finish our tools provided needs to work in conjunction with the tribologists concoctions. Failure isn't an option on hydraulic seals in bores when your John Deere is broken down and it's harvest time for the crops. We also worked closely with, back then, Parker Hannifin, with sealing surfaces compatible with their O ring products. So, I am aware of what causes seizures, and rebuilding and remanufacturing the surfaces, instead of just throwing all new parts at the failure. I also worked at a Fortune 50 aerospace company that made gyro and ring laser gyro guidance systems for the F-14, E2C and AWACS, before GPS, back when Fuel Injected motors were first coming into vogue for pollution control standards. Back then, for me, it was a profession, not a hobby.

So I apologize if I come across as condescending, this sounds like a project that could use some failure analysis as to the root cause. RV-12's are great planes, it's a shame they can get marred by Rotax part failures, long before 2000 hours on the power plant and drive train for the prop. Or it sounds like a great opportunity for an aftermarket parts manufacturer to offer replacement parts that don't fail so soon. Or an oil that works in it's intended application.

Because, something is under engineered, that the failures keep occurring. It could be something as simple as oil jets need to direct oil directly at the parts in question that keep failing, both for lubrication and boundary layer protection.

The good part is there are so many RV-12's already built and flying, with Rotax 912 engines in them, so there's a very large sample of Rotax engines to gather data from in one location.

Don't get mad, just because I think outside of the box. My lack of pilot experience has nothing to do with my experience in engines, and gearboxes, and lubrication issues. It's about how to prevent the failures... unless you enjoy more pulling gearboxes and sending them off to get them fixed and getting handed a bill, than you do flying your RV-12.
No, no owner/operator would be mad, more likely we are confused by your slightly one off dissertations. Have you considered conferring with the manufacturer?
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