Airworthiness Directive
ADSection 12: Continued Airworthiness & Maintenance
Definition
A legally enforceable regulation issued by an airworthiness authority that mandates inspection, modification, operational limitation, or replacement actions on an aircraft, engine, propeller, or appliance to correct an unsafe condition. Compliance with an AD is mandatory for continued operation of the affected product. ADs are issued when an unsafe condition exists or is likely to exist in other products of the same type design.
Where This Shows Up
ADs are the primary regulatory mechanism for addressing safety-critical issues discovered after type certification. They are issued when the authority determines that an unsafe condition exists and that corrective action is required across the affected fleet. An AD typically specifies the affected product (by type certificate, part number, and serial number range), the unsafe condition being addressed, the required corrective action (which may reference a manufacturer's service bulletin), the compliance time, and any acceptable alternative methods of compliance. Operators must track AD compliance status for every aircraft and component in their fleet.
Primary Sources
Airworthiness Directives — the FAA regulatory basis for issuing and enforcing ADs.
EASA regulatory basis for issuing ADs applicable to products type-certificated under EASA oversight.
TCCA regulatory basis for issuing Canadian ADs (CF-ADs) and adopting foreign ADs.
Artifacts Produced
The regulatory document itself, specifying the unsafe condition, affected products, required corrective action, compliance time, and effective date.
Across Jurisdictions
14 CFR Part 39
Published in the Federal Register and tracked in the AD database. FAA ADs are legally binding on all US-registered aircraft of the affected type. Emergency ADs can be issued with immediate compliance requirements.
EASA Part 21, Regulation (EU) 2018/1139
Published by EASA and mandatory for aircraft on EASA member state registries. EASA may also adopt FAA ADs or other foreign authority ADs. EASA ADs reference applicable certification specifications and acceptable means of compliance.
CAR 593
TCCA issues CF-ADs for Canadian type-certificated products and may adopt foreign ADs (FAA, EASA) for products imported under bilateral agreements. CF-ADs are published in the TCCA Airworthiness Directive register.
Related Terms
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