A recent conversation with a technician/IA in Texas centered on work he was performing: An alteration to an engine which involved using a supplemental type certificate (STC).
Several of his questions focused around how the STC should be recorded on Form 337. Is the STC “approved” data, he asked, or is it “acceptable” data? And if it’s “acceptable” data, how should he get the local Flight Standards District Office (FSDO) to “field approve” it.
Two minutes into our conversation I realized that he wasn’t quite sure of the basic definition of the terms we were discussing. “He was not alone,” I told him.
Where does it say I have to use data?
In the bowels of Part 43 sits a pretty important rule that says we have to use “data.” It’s FAR 43.13(a) Performance Rules (general) which says:
“Each person performing maintenance, alteration or preventive maintenance on an aircraft, aircraft engine, propeller or appliance SHALL use the methods, techniques and practices prescribed in the CURRENT manufacturer’s maintenance manual or Instructions for Continued Airworthiness prepared by its manufacturer or other methods, techniques, and practices ACCEPTABLE to the Administrator (FAA).”
This is also the same rule the FAA uses to discourage technicians and repairmen from using unsafe methods to maintain aircraft.
Acceptable data
Acceptable data is found in aircraft maintenance documents such as manufacturer’s maintenance manuals, service bulletins and letters, advisory circular AC 43.13-1A and 2A, and FAR Part 121 and Part 135 air carrier maintenance manuals.
If you read FAR 43.13(a) again, carefully, you can see that the rule allows you to use acceptable data for all maintenance, alterations or preventive maintenance on the entire aircraft.
However, the FAR 43.13 rule, doesn’t say that you can use acceptable data for major repairs and major alterations. You need approved data to handle that!
Approved data
Approved data is data that the FAA has approved and is usually identified as such. Approved data includes: Type certificate data and specification sheets, supplemental type certificates (STC), Airworthiness Directives (AD), manufacturer’s FAA approved data under a DOA, FAA Designated Engineering Representative (DER) data, FAA Designated Alteration Station (DAS) data and appliance manufacturers’ manuals, even though they don’t have “FAA Approved Data” stamped on them.
I suspect the last item, appliance manufacturers’ manuals, is considered approved data because the task of approving countless appliance manuals is near to impossible.
Approved data is required according to the following regulations when making a major repair or major alteration: FAR 65.95(a)(1) Inspection authorization, privileges and limitations; FAR 121.379(b) Authority to perform and approve maintenance, preventive maintenance and alteration; and FAR 145.51(d)(3) Privileges of the certificate.
To summarize, you use acceptable data for all maintenance except major repairs or major alterations. You must use approved data for all major repairs and major alterations.
Solving the problem
With the data definitions out of the way, let’s go back to the IA and the questions he raised. The alteration he was performing happened to be a full flow oil filter installation on a Continental engine. The oil filer installation met the definition of a major alteration as defined in FAR 1.
As a major alteration, it required approved data. Since the kit he was installing contained all the STC paperwork and installation instructions he already had the approved data. This made his life a little easier because he did not need an FAA field approval. All he had to do is fill out Form 337, describe the work performed, and the approved data used (STC). Finally, he must give the owner the Form 337 and send a copy to the local FAA office inside of 48 hours.
This article first appeared in the March/April 1991 issue of Aircraft Technician
