Airworthiness Directive (AD)
Last reviewed · By Chad Griffith
An Airworthiness Directive is an FAA-issued legally binding document under 14 CFR Part 39 requiring inspection, modification, or repair of an aircraft, engine, propeller, or appliance to address an unsafe condition. ADs are the FAA's primary mechanism for mandating safety actions across the fleet of affected aircraft. Compliance is mandatory for all aircraft operated under any operating Part. Two primary categories: inspection ADs (require inspection with corrective action only if defect found) and action ADs (require specific action without inspection alternative). Some are recurring; some are one-time. Compliance is verified at every annual inspection.
Frequently Asked Questions
What's the difference between a Service Bulletin and an AD?
A Service Bulletin (SB) is issued by the manufacturer recommending action — generally voluntary unless contractually required. An AD is an FAA legally-binding directive requiring action — mandatory for all affected aircraft. Many ADs originate from manufacturer SBs that the FAA elevates to mandatory status when safety concerns are identified.
How are AD compliance dates structured?
ADs specify compliance times by calendar date, flight hours, cycles, or 'next inspection' (whichever comes first). Operators must track compliance against these criteria in real time. Recurring ADs (e.g., every 100 hours, every 500 hours, annually) require careful tracking to avoid lapses. Missing a deadline grounds the aircraft until compliance is achieved — operating beyond the deadline is a regulatory violation.
Can AD compliance be delayed?
Generally no. Extensions or alternative methods of compliance (AMOC) require formal FAA approval. AMOCs allow alternative actions equivalent to the AD requirement and require demonstration of equivalent safety. Late or non-compliance is a regulatory violation regardless of cost or operational impact.
How are AD records documented?
Per 14 CFR 91.417, AD compliance must be documented in maintenance records: AD number, AD revision (if revised), date or aircraft time of compliance, method of compliance (inspection result or action taken), authorized signature, and certificate number. AD records become part of the permanent maintenance history.
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