ABCs & FAQs about STCs & PMAs

March 2014

This month’s ShopTalk presents an overview of the procedures for obtaining a FAA Supplemental Type Certificate and Parts Manufacturer Approval. Long time MAPA Log readers may have noticed, over the last several years, fewer ShopTalk articles. That was due to my commitment for my company, KNR, Inc., to obtain three STCs and a PMA.

KNR's first STC started in late 2005 with the silly idea of offering a common sense instrument panel upgrade for pre-1969 Mooneys. Owners could retrofit their panels providing a logical layout (that complies with current FARs) including center stacked radios and complimented by modern pull type circuit breakers.

Now, three STCs later, I can explain why that STC sun-visor kit (or any other STC kit) with about three dollars worth of plastic and ten dollars of hardware costs 450 bucks. But first some acronyms commonly used when explaining this process.

ACO FAA Aircraft Certification Office

MIDO FAA Manufacturing Inspection District Office

DAR Designated Airworthiness Representative (FAR 183.33)

DER Designated Engineering Representative (FAR 183.29)

PMA Parts Manufacturer Approval (FAR 21.303)

STC Supplemental Type Certificate (FAR 21.463)

PSCP Project Specific Certification Plan

QCM Quality Control Manual

GARA General Aviation Revitalization Act of 1994 (Public Law 103-298)

337 FAA form for completing major alterations or repairs

8300.10 FAA airworthiness Inspectors Handbook (FSDO inspector)

Here is how the STC process works. First, you must have an idea of what you want to offer and the size of the market. The second item specifically doesn't concern the FAA but you must be able to delineate what make(s) and model(s) of aircraft and the applicable serial number range. The FAA holds you to this and there is no fudging these numbers; you are locked in.

MAPA Log, January 2004, discussed the mechanics of KNR's first STC, but the FAA paperwork process is another story. Before the FAA will begin talk to you, an STC application must be submitted to the local ACO office. This office is staffed with aeronautical engineers that may or may not know a Piper Archer from a Mooney TLS Bravo from a Boeing 777.

Once you have discussed your STC project and have submitted a written product description and assisting DAR and DER list to the FAA ACO (the PSCP), a project number is assigned to your STC. With a project number, all part fabrication drawings and supplier lists as well as other inspections, reports, manuals, approvals, etc. must be completed and submitted on an agreed schedule. Here is a typical list of items to be completed (as per the PSCP):

Preliminary Kickoff Meeting

Project Specific Certification Plan (PSCP) submitted

Application Accepted

Kickoff meeting

Special Conditions

Data submittal(s)

Drawings and master data list

Analysis reports

Flight Manual Supplement

Instructions for Continued Airworthiness (ICA)

Company test reports

Test plan submittal(s) (structural, systems, flight, noise, emissions, fire protection, emergency provision, etc.)

Test plan approval

Conformity requests




Installation compliance inspection

Type Inspection Authorization (TIA)


FAA test report(s)

Final data submitted to FAA (final drawing and report revisions conformity completion memo, etc.)

Issuance of approved Flight Manual and AFM supplements

Issuance of Certificate

You will have to make or procure all parts and show the FAA during a conformity inspection that all the parts match their respective drawing in dimension and material composition. There must be a working, conforming prototype.

The DER(s) rated in the areas applicable to the STC must sign off on 8130 forms stating that all the parts meet their respective drawings and conform to applicable FARs. The forms are then submitted to the FAA for their blessing.

Now comes the hard part. Complete assembly drawing(s) showing all the parts and their relationships along with a detailed installation manual must be provided. For a sunvisor kit, that's pretty straightforward. For an instrument panel retrofit kit or oil cooler modification, it can be daunting.

Remember, one cannot assume that anyone at the FAA knows anything about the aircraft you are modifying. Think about writing a manual for how to assemble a peanut butter and jelly sandwich and the person reading the manual doing the work doesn’t know what peanut butter is or what a butter knife is or what a refrigerator is, or jelly... you get the idea (don't forget to include the sandwich's flammability tests)

Once you have submitted all your drawings and manuals for assembly, fabrication and installation along with your request for STC and your DER's structural engineering reports, a small forest has been sacrificed. All these documents must have a revision status and their own drawing number with an index so one can easily locate a specific drawing. The completed kit and all the individual parts must have their own part numbers. Unique parts that are not standard hardware must be labeled. An inventory list of the components of a complete kit is a good thing but not necessary for the FAA.

If you have dotted all the I-s and crossed all the T-s and the conformity tests are passed, the FAA ACO will issue you an STC if they can’t think of anything else for you to document. The first STC KNR undertook required two years to complete.

OK, the product is approved, the STC issued and the kit is ready to sell to customers, so we can begin to recoup revenue expended trying to complete this STC. Not! Parts can't be sold unless the manufacturer has a PMA for that specific STC!

To obtain a PMA you must first have an STC. A PMA manual must be created and, just like the STC process, there are no cookie cutter templates for this. A PMA manual is basically a quality control manual (QCM) that the FAA MIDO and the applicant settle on, based on how complicated the STC is and what the MIDO will accept. At this point, another DAR must be hired to guide in the creation of the manual.

This QCM must include some basic items, such as the processes necessary to produce all parts. All parts must conform within stated tolerances to their STC drawings.

It must also show how the applicant plans to segregate all raw materials for the STC parts, usually with a plan view of the PMA holder's facility. A log is kept of the calibration of all tools used to conform each new part manufactured and an incoming entry and inspection sheet for each part needed including raw materials.

All parts such as standard hardware and raw materials must have a manufacturer's statement of composition and lot number so they are traceable back to the original manufacture. For instance, if a piece of 2024T3 aluminum is utilized, it must meet the proper heat treatment and composition and a certificate must be supplied by the aluminum manufacturer, conforming to the required material listed on that part's associated STC drawing. The PMA holder must keep that certification on file for as long as that particular fabricated part is in service (usually forever)! The PMA process is a cradle to grave paper trail on all parts in the STC kit.

When a part is made by the PMA holder he must complete a manufacturing work order showing sources of raw materials and the approved drawing the part was made from. The completed part is inspected and if it conforms to it's fabrication drawing it is marked and placed in a segregated place from raw materials with other finished/approved parts, as per the PMA manual.

The FAA MIDO requires an approved supplier list to be kept on file along with the location inside your place of business where all these PMA parts are kept. The PMA holder must also keep all the scrap material and it must be labeled so one can tell what lot number it came from. If a part made from raw material were to fail that part and its associated scrap can be tested to verify the material certificate the PMA holder got when the raw material arrived has not been falsified.

As if this was not enough, the FAA MIDO can pay a visit to you or your suppliers to insure that the PMA manual is being followed. I have been through two of these inspections. Typically, the MIDO inspector pulls one finished part and asks to see all the paper work for that individual part. Also, that and other parts are checked against masters and conformity tools are verified for calibration in accordance with the requirements of your PMA manual.

The most recent of the three STCs we have obtained required conformity flight testing. Of course, that added additional complexity for the technical issues. But, also, required navigating the labyrinth between the Los Angeles ACO and the Denver ACO. That story is maybe for another ShopTalk.

Lately I have read several articles about how the FAA is mandated to simplify the certification process. Don’t hold your breath. Thirty-five years of experience in this business allows me to predict the regulations getting tighter, not looser. I hope I'm wrong.

Why not do a field approval? About two years ago, the FAA updated the 8300.10 Inspectors Handbook by adding 149 pages clarifying just which field approvals can and cannot be done by the FSDO inspector. Fortunately the update did state that if the applicant for field approval already held an STC in that area requested, the FSDO inspector could complete a field approval. So if you hold an STC, you can get a field approval; if you don’t, you are out of luck.

It boggles the mind why anyone would do an STC of any kind when one looks at the rate of return in Part 91 piston engine aircraft. By the time the DERs and DARs are paid along with the lost shop time of completing the proper paper work to obtain the approvals and the conformity process, it turns out to be too expensive to complete an STC and be able to market it for profit.

It was not this way 35 years ago. I have seen STC drawings that were so poor they appear to have been submitted to the FAA on a bar room napkin. Thirty-five years of progress have created a bureaucracy (the FAA) that is crippling much growth in our industry. I know many pilots that are waiting for the FAA to allow possession of a valid driver’s license in lieu of a 3rd class medical exam. Don’t hold your breath on this one either. For an insight into the history of the FAA's official attitude toward the aviation industry, see the FAA Reauthorization Act of 1996. Their mandate went from "promote" to "encourage." I think it is more negative than that now.

The medical requirements and the STC/PMA requirements are two shining examples of an over-regulated industry that is dying a slow death. It will take an act of congress to change things in our industry as the FAA no longer has a mandate to promote General Aviation and no one in the FAA is willing to put their neck on the line to deregulate our industry in any way. That’s the sad truth.

Of course, DERs and DARs don’t work for free. They work with the FAA but are independent contractors and must charge for their time. In General Aviation, we fight battles against the Feds adopting user fees, but we have lost the war. By utilizing DARs and DERs, important functions that the FAA has covered in the past are now shifted to the private sector and paid for by the consumer. In this case, engineering verification for FAA certification is paid for by the manufacturer and passed along to the user through higher prices. It doesn't make much difference if the vehicle operates at 12,000' and 200 knots or FL390 and Mach 0.82; KNR or Boeing, the level of FAA paperwork is nearly the same.

As always, if you have a question about this article, you can contact me at my aircraft repair shop, at 307-789-6866 or via e-mail. Until the next ShopTalk enjoy flying your Mooney.