An airworthiness directive (commonly abbreviated as AD) is a notification to owners and operators of certified aircraft that a known safety deficiency with a particular model of aircraft, engine, avionics or other system exists and must be corrected.
If a certified aircraft has outstanding airworthiness directives that have not been complied with, the aircraft is not considered airworthy.
- that the aircraft may not be in conformity with its basis of certification or of other conditions that affect the aircraft's airworthiness, or
- Those of an emergency nature requiring immediate compliance prior to further flight, and
- Those of a less urgent nature requiring compliance within a specified period of time.
Issuance
ADs are issued by most civil aviation regulatory authorities, including:
- Civil Aviation Safety Authority (Australia)
- European Aviation Safety Agency
- Directorate General of Civil Aviation (India)
- Federal Aviation Administration (United States)
- Civil Aviation Authority of New Zealand
- Transport Canada
- Standard AD process: Notice of Proposed Rulemaking (NPRM), followed by a Final Rule
- Final Rule and Request for Comments
- Emergency airworthiness directives – issued without time for comment. This is only used issued "when an unsafe condition exists that requires immediate action by an owner/operator...to rapidly correct an urgent safety of flight situation."