We have touched on Parts Manufacturing Approvals multiple times; "What is a PMA" and "Two ways to obtain a PMA". Those posts covered the vast majority of PMAs that will be encountered, but there are special cases that I have been contacted about recently and they are life limited Parts Manufactured Approvals and PMAs with Airworthiness Directives (AD). Let’s talk about these for a moment.
In short, can you get a PMA for a life limited part? Yes. There is a “but” that should be there, because any small differences to the part, might require the applicant to obtain an STC. AC 21.303-4 Paragraph 12 briefly addresses this topic and gives information on what may be needed. With a “common” Test and Computations PMA, some applicants will propose slight material changes, expanding part tolerances outside OEM ranges (for ease of manufacturing), and alternate material processes. With a critical part, you can propose those things but there will be significant testing to ensure you understand all aspects of the part, how the change affects the next higher assembly (NHA), and how the total system is affected. There will have to be approval of PSCP and test plans, do not expect a turnaround time of 1-2 months, it needs to be understood that this is a significant undertaking.
Now on to PMAs with ADs, searching applicable FAA databases for Service Bullets, Service Difficulty Reports, and Ads are required activities (Reference AC 21.303-4 Paragraph 16(c) ) for all PMA Certification Packages, but what happens when your proposed part has an AD? An article with an AD does not mean it is automatically not eligible for PMA, but it does mean there will be additional showings of compliance. The certification package must provide evidence that your article does not reproduce the unsafe condition that the AD was levied against. Why would the FAA let you re-produce a part with known issues? There are two approvals that are required; your geographical ACO finding your design compliant and the ACO that issued the AD; these might not be the same ACO. The ACO that issued the AD must issue an Alternate Means of Compliance (AMOC) letter and the responsible ACO may include this in your notification letter of PMA supplement.
I know that was brief discussion of these two important topics and they were covered at the 30,000 feet level. Each part application can get very detailed and are nuanced as the best way to handle the unique challenges that Life Limited and AD PMAs can present. If you are needed assistance with your certification package or just need general guidance, please do not hesitate to contact us. We will love to hear from you.
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