PMA Parts Marking and Approval: A look at the regulations

PMA Parts Marking and Approval A look at the regulations By Fred Workley In today's cost-conscious environment the use of PMA parts is growing. But there are standards and regulations that have to be met. The following article will take a...


Part marking requirements are also addressed in FAA Order 8110-42A. Parts produced under a PMA must be permanently and legibly marked in a manner that will enable persons to identify: the fact that it is a PMA part, the manufacturer, the part number, and the type certificated product(s) on which it may be installed. In the case of a part based on an supplemental type certification (STC), the identification of installation-eligible type certificated products must include reference to the STC on the shipping document. In the case of parts that have been identified as critical components, the part must be marked with a part number or equivalent, and serial number or equivalent. The identifying marks should be included on the design data and reviewed as part of the FAA engineering approval of the design to establish that the location and process of identification does not degrade airworthiness compliance. The issuance of the PMA letter authorizes (and requires) the PMA holder to mark the parts in accordance with the approved design. If a PMA is granted for an assembly, detail parts of the assembly sold separately must also be accompanied by shipping documents containing the information required by Part 45 § 45.15 and reference the assembly PMA part number.

The PMA part should be numbered such that it is distinguishable from the specific Type Certificate holder's part number. The TC holder's part number with a prefix or suffix is sufficient for this purpose, so long as use of such a prefix or suffix will not cause confusion with the part marking practices of the TC holder. The requirement to mark with name, trademark, or symbol of the applicant may be satisfied by the use of a prefix or suffix, if the prefix or suffix is consistent across the applicant's product line. The FAA-PMA letter shows the type-approved part number with which the applicant's part is interchangeable. Each part must also be marked with the letters "FAA-PMA" in proximity to the part number. Part marking information is necessary to ensure that compliance will not interfere with airworthiness considerations.

A holder of a PMA, Approved Production Inspection System (APIS), or TSOA (Technical Standard Order Authorization) controls the design and quality of a product or part. The Production Approval Holder (PAH) is the holder of a Production Certificate (PC). For a supplier to a PAH, in which the supplier's part number is used by the PAH, the PMA holder may use the same part number as the design approval holder to permanently mark the part (in the same area as the part number) with the letters "FAA-PMA" and the name, trademark, or symbol of the PMA holder.

Some parts are impractical to mark, are too small, or have other characteristics of special concern. Information not marked on the part must be put on a tag that is attached to the part or marked on the container for the part. If the number of type certificated products on which the part is eligible for installation is too long to be practical to include with the part, or if the list is likely to change over time, the tag or container may refer to a readily available manual or catalog made publicly available for part eligibility information by the PMA holder.

When the PMA is issued by showing evidence of a licensing agreement, the PMA part number may be identical to that on the type certificated part to permanently mark the part with the letters "FAA-PMA" and the name, trademark, or symbol of the PMA holder.

Under a licensing agreement, when the applicant has been given the right to use the TC holder's design, which includes the part number, and a replacement part is produced under that agreement, the part number may be identical to that of the TC holder, provided that the PMA holder includes the letters, "FAA-PMA," and the PMA holder's identification symbol is on the part. In all other cases, the PMA holder's part number must be different from that of the TC holder.

Parts replacement and modification

FAA Order 8110-42A also establishes procedures for the evaluation and approval of Parts Manufacturer Approval (PMA) for replacement and modification parts. The procedures contained in this order apply to all engineering and manufacturing personnel. We will review the guidance for designating a PMA part.

This order describes the procedures for FAA personnel to follow when issuing a PMA. Comprehensive guidance is provided on making compliance findings by identicality and test/computations. It is intended that for most nonidenticality approvals, that these procedures will be used and that STC procedures should only be used where the PMA application constitutes a major change to the product unless the applicant is applying on the basis of an STC or identicality by licensing agreement.

14 CFR Part 21 § 21.303 requires that any person producing replacement or modification parts for sale for installation on a type certificated product obtain a PMA or produce such parts under one of the exceptions of Part 21 § 21.303(b). PMA may be obtained for replacement parts for TSOA articles that are approved as part of a product type design, provided that installation eligibility of that product can be shown. However, approval of a part that would constitute a major design change to the TSOA article can not be done under PMA and would require a new TSOA. An applicant's design that could meet the identicality provisions of Part 21 § 21.303 would normally not be considered a major design change.

The design must meet the applicable airworthiness standards. There are two basic ways that an applicant may show compliance: through a type certificate or through tests and computations. The applicant must assure that no interference with mating or adjacent hardware occurs and that the part performs its intended function.
Regardless of the basis upon which PMA is sought, the data must include information that meets the requirements of Part 21 § 21.303 (c) and the airworthiness requirements of the FARs applicable to the product on which the part is to be installed. The information required may extend to the manufacturing controls, fabrication processes, assembly techniques, and the performance, endurance, and test requirements if they are necessary to establish the airworthiness of the part in accordance with applicable regulations.

Installation eligibility requires detailed identification of and information on the part sufficient to demonstrate understanding of where the part goes, on which products it may be installed (make, model, series, and if appropriate serial number), how it relates to the next higher assembly of which it is a part, and the consequences for the next higher assembly and the product if the part should fail. If by STC, a copy of the STC will be sufficient to show eligibility.

Maintenance instructions for continued airworthiness
Part 21 § 21.50 (b) states that a holder of a design approval, including a TC or STC, for a product for which application was made after Jan. 28, 1981, must furnish a complete set of Instructions for Continued Airworthiness (IFCA) prepared in accordance with the airworthiness requirements applicable to the product. If the part for which PMA is sought would be eligible for installation on a product for which application was made after that date, the PMA applicant must furnish data sufficient for the FAA to determine that the IFCA will continue to be valid for the product with the PMA part installed. If the IFCA are not valid with the PMA part installed the applicant will need to furnish supplementary IFCA. For parts which would be eligible for installation only on a product for which the application for TC was made on or before Jan. 28, 1981, the PMA applicant must furnish supplementary maintenance and related instructions, if the design approval holder's instructions are not adequate.

To show compliance with the applicable airworthiness standards under test and computation, the applicant must provide analysis, supported by an appropriate test design and results. The analysis must be supported by the engineering assessment of the consequences to the next higher assembly and the product, if the part fails to perform its intended function.

"Identicality" can be based upon "reverse engineering." The process of reverse engineering is one way to develop the design of a part. However, reverse engineering a part will not normally produce a design that is identical to a type certificated part. While an applicant could establish the use of identical materials and dimensions, it is unlikely that a showing could be made that the tolerances, processes, and manufacturing specifications were identical. If the design can not be approved by identicality then the test and computation method should be used. The applicant must show that its design complies with the applicable regulations. The extent of substantiating data required by the FAA should take into account the degree to which the design is identical.

The PMA may be granted if the applicant has shown on the basis of tests and computations that the part meets all applicable airworthiness requirements.

Furthermore, the applicant for a PMA must establish and maintain a fabrication inspection system (FIS) to meet the requirements of Part 21 § 21.303(h). It is suggested that the FIS be in the form of a manual describing the methods, procedures, inspections, and tests which the PMA holder and his suppliers intend to use to meet the requirements of Part 21 § 21.303(h)(1)-(9), provisions for reporting under Part 21 § 21.3 and provisions for identifying the product in accordance with Part 45 § 45.15.
While the use of PMA parts reveals a focus on the bottom line, don't forget that the FAA's focus is safety and accountability.


Fred Workley is the president of Workley Aircraft and Maintenance Inc. in Alexandria, VA, Benton City, WA, and Indianapolis, IN. He holds an A&P certificate with an IA, general radio telephone license, a technician plus license, ATP, FE, CFI-I, and advance and instrument ground instructor licenses.

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