§ Mr. Mullin
The purpose of airworthiness directives is to specify actions which are necessary to ensure the continuing airworthiness of particular aircraft. An airworthiness directive will normally apply to a specific type of aircraft.
Airworthiness directives will normally be issued by the State which is responsible for the design of an aircraft. The Civil Aviation Authority requires all aircraft on the UK register to comply with airworthiness directives issued by the State of Design. In addition, the CAA may issue airworthiness directives relating to any UK registered aircraft if they believe it necessary for the safe operation of the aircraft.