Airworthiness Directive

An Airworthiness Directive (AD) is a legally enforceable rule issued by a civil aviation authority (FAA, EASA, ANAC, etc.) that mandates specific inspections, modifications, or operational limitations on an aircraft, engine, propeller, or appliance to correct an unsafe condition.

ADs are issued when an aviation authority determines that an unsafe condition exists in a product and that condition is likely to exist or develop in other products of the same type design. Compliance with ADs is mandatory — an aircraft cannot legally fly if it has outstanding, overdue ADs.

ADs may require one-time inspections, recurring inspections at specified intervals, or permanent modifications. They can be issued as Emergency ADs (requiring compliance within days or flight hours) or Standard ADs (with longer compliance timeframes).