Airworthiness Directive
An Airworthiness Directive (commonly abbreviated to AD) is a notification to aircraft owner/operators of a known safety issue with a particular model of aircraft, engine, avionics or other system.
ADs in the USA are issued by the FAA and may be categorised as voluntary, mandatory or emergency.
- Voluntary AD - Operators may choose whether or not to comply.
- Mandatory AD - Operators must comply within the timeframe included in the directive
- Emergency AD - Operators must comply immediately.