Airworthiness Directives Explained
What an AD is, why compliance is mandatory, the difference between one-time and recurring ADs, and how an owner tracks and records them.
An Airworthiness Directive (AD) is the FAA's legally binding notice that an unsafe condition exists in an aircraft, engine, propeller or appliance, and that action is required to correct it. ADs are issued under 14 CFR Part 39, and no person may operate a product to which an AD applies except in accordance with that AD.
Why they are mandatory
Unlike a manufacturer's service bulletin (which is generally advisory), an AD is a regulation. Ignoring an applicable AD makes the aircraft unairworthy — regardless of how well it seems to fly. Compliance is the owner/operator's responsibility.
One-time vs recurring
- A one-time AD is satisfied by a single action — an inspection, a modification, a part replacement.
- A recurring AD must be complied with repeatedly at a stated interval (e.g. every 100 hours or every 12 months). Recurring ADs are the ones owners most often overlook.
Tracking and records
Every applicable AD, its method of compliance, and the date and time of compliance must be recorded in the maintenance records (14 CFR 91.417). At each annual inspection the IA reviews the AD status. A current AD compliance record is one of the first things to check when buying an airplane — an open recurring AD is a hidden liability.
Finding them
ADs are published in the Federal Register and catalogued in the FAA's online AD database, searchable by make and model.
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*Reference and training only — not for navigation or as legal advice. Always consult the current 14 CFR, the AIM, your aircraft’s POH/AFM and a certificated flight instructor.*