FAQ n.19493

When an unsafe condition affects a certain Part Number, the AD applies to all aircraft for which installation of the part is eligible. The reason for this is that the unsafe part could be installed on any of those aircraft at a later stage after issuance of the AD. The AD would contain a prohibition to install, or specify the conditions under which installation would be allowed, which are requirements that must also apply to aircraft that do not, on the effective date of the AD, have the part installed.