Monday, November 28, 2011

Suspect Un-Airworthiness

Letter received from a friend:

The pic is of a freshly topped XYZ engine. We sent it back to XYZ cause we had metal in the filter and because they had fitted the wrong rockers. This engine is on it's third camshaft since last overhaul. Pilot  is not happy with the vibration and missing.  Pull filter and there are 2 strings of red silastic and metal.  As you can see in the pic, they have put silastic between the case and the cylinder base. Suprisingly they have had a rash of through bolt and stud failures. Can't imagine why. They just don't see a problem. You'll love this; they rang and said that at oil change time should be pretty normal to find a match head of metal in the filter, comes from the cam and wear on the cylinder walls. I'm now the baddy in this. If I let it fly and the engine packs up over rough country, I'm in the gun. If I dig my toes in, will they strip it and admit it has something wrong.

So what do you do when you discover serious problems with an engine and the manufacturer's service rep tells you "it's normal" don't worry? "Put it in writing" is my immediate response but beyond that how do you approach the problem? Here is my suggestion.

You can go round-and-round on what is "normal" and what is "airworthy" with manufacturer's and repair agencies but this misses the point. They all work to an approved process that is kept in check by their quality control system. Deviations to the approved process that escape the quality system are evidence of a process deviation and a quality system break-down. Product released during the time of deviation is an escape and is not approved nor airworthy because it does not, or is suspect, as being not in conformance. Part of the definition of "Airworthy" is that the the part conforms to its type design." Airworthiness is not the determination by the companie's service rep that unapproved material in the oil system is normal.

The exact nature of the non-conformance i.e. silastic or bits of metal, is not the issue. The issue is that the engine escaped their quality system, has suspect deviation from their quality process and is therefore "not airworthy" The product can only be re-inspected and made airworthy after the process and QC system is brought back into compliance as evidenced by corrective action and audit to confirm that the "corrective actions" are successful. 

It appears that there is a break-down in their quality control system. I would not accept repairs as "approved" or "airworthy" during the time of non-conformance. Can they provide the date of the last quality audit and what corrective actions have been made? I would be concerned that your response was an individual opinion and does not reflect the requirements of their quality system. 

Put your concerns in writing. Send it to XYZ with a copy to the owner and whatever you call your "FAA". Any decision is outside of your area of expertise -- you can only express a "concern" Let engineering "XYZ" and standards "FAA" make the decision.

I have seen a Lycoming failure caused by a "match head' size of Silastic that entered the oil system and stuck at the rod bearing oil port where it starved the rod bearing of oil. My recommendation based on experience is to fully inspect all oil passageways for unapproved material.

Normal wear does not occur as metal chunks. 

Parting sealant "Silastic" loose in the engine indicates that gasket material has extruded from between the parting surfaces causing cylinder-to-crankcase embedment relaxation. I doubt joint loosening caused by gasket extrusion meets design intent.

----------Another potential action you might take if circumstances apply------------

Since you must determine if the item is airworthy (Airworthy. To determine that the installation of a part complies with the applicable  regulations, the installer of the part is ultimately responsible for establishing that the part conforms to its type design and is in a condition for safe operation.). AND you suspect that it might not be then (at least in the US) you can file a SUP  if the company is a PAH Production Approval Holder. A Suspected Unapproved Part (SUP) is "new parts that have passed through a PAH’s quality system which do not conform to the approved design/data." AC No: 21-29C Change 1, Definitions p. Unapproved Part(2)

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