Definition
A legally binding notice issued by the FAA when an unsafe condition is found to exist in an aircraft, engine, propeller, or appliance. The directive specifies the corrective action that must be taken, the aircraft or components affected, and the time frame within which compliance is required. Operating an aircraft that is not in compliance with applicable ADs is prohibited.
Plain English
An official FAA order that says: a problem has been found on this kind of aircraft or part, and here is what you must do about it, and by when. You cannot legally fly the aircraft until the required work is done.
Context Anchor
Seen in aircraft maintenance records, logbooks, inspection paperwork, and discussions about whether an aircraft is legal and safe to fly.
Derivation
Airworthy combines 'air' with 'worthy,' meaning fit or suitable for flight. A directive is an official instruction that must be followed, from the Latin 'directus' meaning 'made straight' or 'guided.' Together: an official, mandatory instruction to keep the aircraft fit for flight.
Why Pilots Care
Compliance is mandatory by regulation. Failure to address an AD can ground the aircraft and create serious safety or legal consequences.
Analogy
Similar to a mandatory recall notice on a car that must be completed before the vehicle can be driven legally.
Intuition Check
Do not read “directive” as a suggestion or general recommendation. In this context, an Airworthiness Directive is a mandatory FAA requirement when it applies.
Example Sentence 1
Before the flight, the pilot reviewed the maintenance logbook to confirm all applicable airworthiness directives had been complied with.
Example Sentence 2
An AD note required inspection of the wing spar attach bolts after reports of fatigue cracking in the fleet.