The Difference Between PMA and STC

Posted on January 17, 2019 James Williams The Difference Between PMA and STC

One of the hardest things to do in the aviation industry is to deal with parts. An aircraft’s life can be long, but the same can’t be said for all of its parts. Some parts have to be replaced more frequently than others. And sometimes, you may need to replace these parts only to find out that they are no longer being manufactured. Luckily, there are procedures and authorizations in place that allow you to get the parts you need. To start, you can look at the original manufacturer part numbers, alternates, and PMA parts. Alternatively, you can look into alternate part numbers that have one-way or two-way interchangeability.

Parts Manufacturer Approval (PMA) is a direct authorization to a manufacturer from the Federal Aviation Administration (FAA) to produce aircraft parts although they may not be the Original Equipment Manufacturer (OEM). PMA is a combination of a design approval and production approval by the FAA to a manufacturer. In layman's terms, PMA parts are FAA approved parts.
A majority of the time the PMA parts will have alternate part numbers yet still have the same functionality as the OEM part. Approval for the PMA requires the FAA’s thorough analysis, maintaining airworthiness and identical design. It is especially common when the OEM is no longer manufacturing a part or no longer in business. 

Alternatively, Supplemental Type Certificate (STC) is a design approval by the FAA to modify the current design of a part. STCs are typically used when there are no alternative parts or replacements available. STC involves an elaborate certification process in which the materials are tested, engineering is analyzed, and a prototype is manufactured and tested for compliance and conformance. Each design change and variation from the OEM part is listed and documented.  The STC is useful when there are additional modifications needed to be made to a part. But, it’s a design approval only and has no inherent production approval like a PMA does.

Aerospace Purchasing, owned and operated by ASAP Semiconductor, should always be your first and only stop for all your aircraft parts related needs.  Aerospace Purchasing is a premier supplier of OEM and PMA aircraft parts, whether new or obsolete.  We’re available and ready to help 24/7x365.  If you’re interested in a quote, email us at or call us at +1-714-705-4780.

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