The Complexity of PMA and STC Approvals

Recently I was touring a new MRO facility and the host managers were discussing authorized repair capability, PMAs, and expediting STCs, and I recognized that it was time for refresher training on the definition and applicability of those acronyms. A...


Recently I was touring a new MRO facility and the host managers were discussing authorized repair capability, PMAs, and expediting STCs, and I recognized that it was time for refresher training on the definition and applicability of those acronyms.

A document search located some standard definitions: PMA — Parts Manufacturer Approval “is an approval granted by the FAA to a manufacturer of aircraft parts. PMA-holding manufacturers are permitted to make replacement parts for aircraft, even though they may not have been the original manufacturer of the aircraft.” STC — Supplemental Type Certificate “is issued when an applicant has received FAA approval to modify an aircraft from its original design.”

When reading regulatory documentation, I usually start to drift after about 10 minutes so my preferred learning method is listening to an expert explain how these processes play out in the actual work environment. One segment of our industry that consistently deals with these approval processes are companies that overhaul, modify, and repair airframes and install custom aircraft interiors on corporate jets.

Aviation Fabricators (AvFab) is one of those companies and Jeff Lowe is experienced in obtaining STC and PMA approvals for their production items. Jeff and his father G.R. began operations at their Clinton, MO, facility in 1988 and now have 24 employees.

PMA and STC approval processes

Necessity and profitability appear to be the two reasons why companies pursue STC and PMA authorization. I asked Jeff if he could start at the beginning and provide some insight and detail about the authorization process, which AMTs don’t normally get when we pull a kit or part for a job assignment.

According to Jeff, “Pursuing and getting authorization to make a change or reproduce an aircraft part is an arduous task so we don’t begin the process unless a real need has been defined. All process steps have to be completed before applying for regulatory approval to produce aircraft parts. It is time-consuming, costly, and requires considerable data collection, pre-production work by specialist(s), then careful analysis, and decision making.”

Speaking to necessity, Jeff explains, “We are constantly challenged to help keep our MRO and Completion Center’s customers’ planes flying as economically and safely as possible. In reality, for any OEM to support everything that ever appeared in their Illustrated Parts Catalog (IPC) is impossible and they would probably go broke if they kept every part in stock for every model of aircraft they ever built. In the case of PMAs, we are not looking to reinvent the wheel, we’re simply trying to duplicate a part to the same quality or above as the original part and at a profit.”

As for profitability, the applicants take all the risk because most of the cost of getting an STC or a PMA is front-loaded. “There is material testing, drafting, engineering analysis, prototype building, compliance and conformity procedures, and production setup costs (not to mention marketing and overhead). We must determine how real and significant the need in the field is, so we can determine an amortization amount for our investment when obtaining the PMA. Time and resources have to be justified. On average it takes nine months to a year to obtain an STC approval and add that to the PMA listing. In the past few years we have received around 10 PMA approvals for replacement parts and probably 15 STC approvals which were also added to our PMA list.”

When asked to discuss the difference between a PMA and an STC authorization, Jeff explains that there are “some similarities and some significant differences. The development process for getting an STC authorization is similar to a PMA development but the scope and scale of the effort is much greater. Accordingly, the need for an STC typically comes when there is no product that meets a need. It’s usually not a replacement part; it’s a new concept. With the STC, a whole new realm of considerations must be included. How can we best design this product for safety, comfort, weight, installation, removal, and value?

This content continues onto the next page...

We Recommend