The Terms, Parts Manufacturing Approval, And Supplemental Type Certificate Commonly Get Confused

If you’re a recreational pilot operating a small light airplane, the terms “Parts Manufacturing Approval” (PMA) and Supplemental Type Certificate (STC) are easy to get mixed up. It even gets more confusing when your friends, who fly homebuilt airplanes, never seem to care about this stuff but your mechanic gets all huffy when you ask, “Why can't I be just like those guys?”

Here it is in a nutshell. If you’re flying an airplane that is type-certificated, that means it holds a ‘standard airworthiness certificate,’ everything on that airplane is, in one way or another, FAA approved. If you’re going to replace a part, or change something in the airplane, the PMA and STC come into play.

PMA
When your type-certificated airplane is approved by the FAA for certification, it has to meet various levels of FAA criteria; that means every part on the airplane. A type-certificated airplane comes complete with something called a ‘Type Certificate Data Sheet,’ which determines many of these requirements.

Any airplane-specific part that is replaced must either be provided by the manufacturer, or be approved by the FAA as being the same as, or better than, the manufacturer provided part. That part would be referred to as being a PMA part. PMA part is for the replacement of existing parts, and does not apply to the changing or modification of aircraft equipment; that requires an STC.

STC
An STC is issued when an applicant has received FAA approval to modify an aircraft from its original design, meaning that it does not comply with the original type certificate data sheet.  The STC, which incorporates by reference the related type certificate, approves not only the modification but also how that modification affects the original design.

An STC might be required for something as simple as installing an upgraded seat belt system, or as complicated as changing the wing design.

An example of a newly created STC was recently announced when the EAA worked with the FAA and Dynon to establish an STC for the Dynon EFIS-D10A to be installed on an FAA type-certificated airplane as the primary attitude reference indicator.

This STC has to be applied to specific aircraft models, and someone wanting to use this STC for such an installation will go through EAA to acquire it. This was a significant step in that it now allows the Dynon unit, which was previously only used for experimental airplanes, to be used in type-certificated aircraft.

Remember, all of this only applies to type-certificated airplanes, amateur built experimental aircraft hold a special airworthiness certificate (different from a standard certificate) and do not get involved with the requirements for STC’s or PMA parts.

(Image from file)

FMI: www.faa.gov