How can revisions to an Airworthiness Directive be identified?

Revisions to an Airworthiness Directive (AD) can be identified through the AD number, which typically consists of a series of numbers and letters that indicate the order in which the ADs were issued. The AD number also reflects any revisions. For instance, the original AD might carry a basic number format like 2021-01-01, while revisions would include a suffix such as 2021-01-01R1, clearly indicating it is a revised version of the original directive. This systematic numbering provides an easy reference for maintenance personnel to identify the most current requirements.

The other options do not reliably indicate revisions. The number at the bottom of the AD isn’t standardized to convey revision status. The first paragraph of an AD might provide context or summarize the directive, but it does not serve as a formal identifier of revisions. The signature of the FAA administrator is essential for validating the AD but does not provide an indication of its revision status. Thus, the AD number is the most direct and informative way of tracking changes to the directive itself.