The standard AD process is to issue an NPRM followed by a Final Rule. After an unsafe condition is discovered, a proposed solution is published as an NPRM, which solicits public comment on the proposed action. After the comment period closes, the final rule is prepared, taking into account all substantive comments received, with the rule perhaps being changed as warranted by the comments. The preamble to the final rule AD will provide response to the substantive comments or state there were no comments received.
Final Rule; Request for Comments. In certain cases, the critical nature of an unsafe condition may warrant the immediate adoption of a rule without prior notice and solicitation of comments. This is an exception to the standard process. If time by which the terminating action must be accomplished is too short to allow for public comment (that is, less than 60 days), then a finding of impracticability is justified for the terminating action, and it can be issued as an immediately adopted rule. The immediately adopted rule will be published in the Federal Register with a request for comments. The Final Rule AD may be changed later if substantive comments are received.
An Emergency AD is issued when an unsafe condition exists that requires immediate action by an owner/operator. The intent of an Emergency AD is to rapidly correct an urgent safety of flight situation. For more infomation, see the Emergency AD page.
An AD is considered no longer in effect when it is superseded by a new AD. The superseding AD identifies the AD that is no longer in effect. There are no compliance requirements for an AD that has been superseded.