1. New §21.9(a)(4) addresses the new classification of commercial parts and their method for being installed on a type certificated article. There is no mention of how these parts can be repaired once installed.
    Would the manufacturer of the commercial part be able to repair these parts or would they have to be repaired under Part 43? If they are to be repaired under Part 43 would the manufacturer have to be considered a uncertificated maintenance provider (provided they were indeed uncertificated)? Would the part require approval for return to service before installation (after repair)?
       The new §21.9(a)(4) provides for a replacement commercial part that does not need further FAA approval regarding the installation of the replacement part. There have been no changes concerning the maintenance of commercial parts installed on an aircraft. Commercial parts may be maintained in accordance with part 43 if instructions for continued airworthiness (ICA) were accepted detailing the maintenance procedures for maintaining the commercial part as part of the approval of the alteration installing the part on the aircraft (§43.13(a)). This maintenance is to be performed by someone authorized per §43.7 and approved for return to services as prescribed in §43.9.
    The requirement of §43.13(a) cannot be met if ICA detailing the maintenance of a commercial part have not been accepted. Therefore, if a commercial part fails or malfunction without having these ICA the only options to repair the aircraft are to remove the commercial part from the aircraft or replace it with a part as prescribed in §21.9(a)(4).
    It should also be noted that a manufacturer is not authorized to perform repairs in accordance with §43.3.

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