How is an Airworthiness Directive (AD) determined as applicable to an aircraft, and what is the typical immediate action when issued as an urgent AD?

• A. AD applicability is determined by the aircraft type and serial, operators must comply; urgent AD requires immediate or expedited action to ensure safety, often with instructions to operate under specified limitations or grounding until compliance.
• B. AD applies to any aircraft regardless of type and serial.
• C. AD applicability is based on model year only.
• D. Urgent AD allows operation without grounding or limitations.

Answer: (A)

Airworthiness Directives apply to specific products, not to every aircraft. They define applicability by the aircraft’s type certification and may include exact serial numbers or configurations that are affected. The directive then prescribes the required corrective actions to those particular airplanes, such as modifications, inspections, replacements, or other procedures to return the aircraft to airworthy status. When an AD is issued as urgent, it demands immediate or expedited action to address the safety issue, which almost always means grounding the affected aircraft or operating under strict limitations until the required work is done. The other statements would misstate how ADs are scoped or how urgency is handled, since ADs are not universal to all aircraft, are not based solely on model year, and urgent ADs do not permit unrestricted operation.