Demonstrating Eligibility

PMAs are unique, in that they are production approvals that also inherently include an eligibility (an installation for which the PMA is eligible).  The PMA application must identify the product onto which the PMA part will be installed (14 C.F.R. § 21.303(a)(1)).  Before 2009, the installation eligibility was required to be printed on the PMA Part.  The 2009 rule change eliminated this marking requirement.  Today, the best place to find standard eligibility information for a PMA part is in the PMA Supplement.  The eligible installation that was revealed as part of the application typically gets carried-over  to the PMA supplement (FAA Order 8110.42D, chg 2, App’x D (sample PMA Supplement)).

The preferred method for expanding eligibility is generating a new supplement (FAA Order 8110.42D, chg 2, para 2-13).

The FAA typically requires a demonstration of eligibility – one that might be separate from the demonstrations of compliance to the applicable Airworthiness Standards.  The FAA has accepted a variety of mechanisms for demonstrating eligibility. One of the most common ways is to show that the article that is being replaced (often called the OEM article) can be found in the instructions related to the product (or the component maintenance manual for the next higher assembly into which the PMA-application article is to be installed).  This can be accomplished by reference to the illustrated parts catalogue (IPC), the instructions for continued airworthiness (ICA), or any other manufacturer’s instructions that are considered acceptable under 14 C.F.R. § 43.13(a) (see FAA Order 8110.42D, chg 2, para 2-4).  Note that FAA guidance advises that IPCs should only be used to confirm eligibility for non-critical parts (over 99% of PMA parts are non-critical so this means that IPCs can be used to support eligibility assertions for most PMA applications) (id.).

Using the relevant page out of the IPC or ICA can be a very effective, but some manufacturers, in an effort to stymie competition, have threatened air carriers with legal action.  We are not aware that this threat has ever resulted in actual legal action against an air carrier, and there is FAA guidance that states that the FAA expects air carriers to share the ICAs with their maintenance contractors (MARPA wrote about this when it was published).  Nonetheless, the threats have spooked some air carriers and thus they have started to provide technical assistance letters in some cases, which verify that (1) the air carrier engineering staff has examined the ICA (or other document), (2) the examination has revealed that the replaced part was listed in the reviewed reference, which is related to the product, and (3) the staff thus concludes that the PMA replacement is therefore eligible for installation in that product to the extent the design makes the PMA a replacement for the replaced article.  Several air carriers and PMA companies have reported to us that this has been acceptable to FAA certification engineers.

This eligibility demonstration is, of course, in addition to the demonstration that the PMA article meets each applicable Airworthiness Standard.

What about adding additional eligible installations?  In an eligibility expansion, the design of the PMA article has already previously been approved by the FAA and therefore does not need to be re-approved.  The only thing that needs to be verified is whether the approved design is eligible for installation on the subsequent product.  In many cases, the PMA part is proposed to be added to another product design that uses the part in the same next higher assembly with the same form, fit, and function.  When this is the case, the lack of physical differences means that the PMA replacement article will perform the same in the new installation, which makes it easy to add the new installation as an additional eligible installation on a revised PMA Supplement.