Production and Air Worthiness Approval and Parts Marking

Comment on [Docket No. FAA–2006–25877; Notice No. 06–15] RIN 2120–AI78 1. Definitions should be derived and added for the following terms: Replacement Part and Modification Part These terms are used repeatedly in both the Federal Aviation Regulations and this NPRM, but neither contains a specific definition of either. The intuitively logical interpretation would be that replacement parts replace a part approved under the original type certificate and modification parts do not. However, this does not seem to be an ubiquitous distinction. Consider Supplement #2 to Parts Manufacturing Association PMA PQ0938SW for a main rotor blade on certain Bell helicopters. The approval is for a Modification Part implying that the aircraft can fly with more than its proper share of main rotor blades. Upon questioning I was advised that the blade was considered a Modification Part because there were differences between the original part and the PMA part. There are currently at least 2,032 PMA's for parts listed as Modification Parts that replace a type certificated part with the term "Identical design" used as the parts design authority. (Contact me if you want a list.) Logically "identical design" means something had to have been copied, yet the approvals state they are Modification Parts. I have asked many people in the industry to define these terms and have received nearly as many definitions as persons asked. Obviously, these terms beg for codified definitions so they mean the same thing to all people. At the October MARPA conference John Milewski gave a presentation regarding this NRPM. One of the items contained in his discussion was the necessity of defining a Modification Part. The NPRM, however, is silent in this respect. 2. To specify eligibility or not. Mr. Milewski also implied at the conference that installation eligibility would no longer be necessary in PMA issuance. When questioned specifically whether eligibility would be disappearing from the PMA supplements themselves he was evasive and did not render a specific answer to the question while at the same time strongly suggesting that eligibility specification on supplements would be gone. The NPRM should state with clarity whether installation eligibility will be a required element for PMA supplement issuance. Jack Buster Aviation Data Research and Modification and Replacement Parts Association