The Federal Aviation Regulations are Debatable

Debating the regulations among professionals is a good thing.


Parts manufacturer approval (PMA) is basically a quality assurance procedure. Order 8110.42B describes the procedures for evaluating and issuing a PMA for replacement and modification parts on type-certificated products. Although approved as replacement parts, aftermarket PMA parts are not necessarily identical to OEM parts. In some instances, the aftermarket PMA part has proven to be an improvement.

Technical Standard Orders

Technical Standard Orders (TSO) is a minimum performance standard. An example would be TSO-C22g, Safety Belts. This TSO prescribes the minimum performance standard that safety belts must meet in order to have the applicable TSO marking. However, to qualify for placing the TSO marking on a part, you must be the holder of the TSO for that part, just as the aircraft manufacturer is the holder of the TC for the aircraft. The most important details to remember about TSO parts is they must have the applicable TSO marking, and they must be specifically approved for installation on the make and model type-certificated product.

Sometimes a TSO may have hundreds of variations such as TSO-C62d, Tires. What approval do you need for the tires on an aircraft? Tire requirements are aircraft performance related. The aircraft maintenance manual should tell you. The Cessna 172 maintenance manual may only specify size and ply rating, while the Cessna Citation maintenance manual may be more specific.

What TSO markings should a tire have? Each tire must be legibly and permanently marked with at least the following:Applicable TSO number, brand name, and the name or registered trademark of the manufacturer responsible for compliance, the speed rating, load rating, size, skid depth, serial number, date, manufacturer’s part number and plant code, and if appropriate, nonretreadable.

Can you fabricate a TSO part? Special Airworthiness Information Bulletin Number ACE-96-01 says, “Hose assemblies may be fabricated by a mechanic utilizing TSO-C53a Type C or D material.” However, if you do that you will end up with a Suspected Unapproved Part (SUP). If you do not hold the TSO, you will have to fill out a Form 337, and with your materials documentation, take your fabricated hose assembly, complete with your new fire-resistant TSO markings identifying you as the manufacturer, to a MIDO or FSDO for FAA approval prior to installation on the make and model type-certificated product.

It’s About Traceability

Traceability is required for ADs. If a part proves to be defective, we need to know where to find and replace or modify parts of the same design from the same manufacturer.

Some time ago, the FAA seemed to relax its documentation requirements for installing other than OEM parts. Part of the reason may have been the ever-increasing workload of processing all those Form 337s for a growing aftermarket business. However, our need to know who made the parts installed in a type-certificated product remains.

Here’s a suggestion. Rather than eliminating traceability, just eliminate the workload. The FAA owns a simple computer program referred to as Program Tracking and Reporting Subsystem (PTRS) that filters and feeds data into a Paradox database. One simple page of that subsystem could easily be developed and made accessible via the Internet and the local FSDO and MIDO for documenting the installation of aftermarket PMA parts. This would eliminate the workload associated with processing all those Form 337s, and traceability efficiency would be tremendous. Retrieving information from a Paradox database is easy and fast. The savings to the public would also be tremendous.

What if the FAA knew which aircraft had which parts installed? I believe the applicability portion of an AD, as well as the mailing list, would be different. Read the applicability portion of any AD from the 1950s, 1960s, or 1970s, and then read the applicability portion of AD 2005-26-10. See what a difference eliminating traceability has made?

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