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An Airworthiness Directive (AD) is a document issued or adopted by the Civil Aviation Authority of the State of Registry of an aircraft (Type Certificate Holders - TCH). For example, TC will adopt all FAA AD’s issued against Boeing products as the USA is the type certificate holder (TCH) for Boeing, and the Canadian aircraft register contains Boeing products.
An AD mandates actions to be performed to restore an acceptable level of safety to an aircraft, when evidence shows that the safety level may otherwise be compromised.
Canadian ADs are issued by the Minister pursuant to the conditions prescribed in Canadian Aviation Regulation, Part V, Subpart 93 (CAR 593). Pursuant to CAR Part VI, Subpart 5, section 84 (CAR 605.84) and the further details of CAR Standards (Airworthiness Manual) 593 and 625, the continuing airworthiness of a Canadian aircraft is contingent upon compliance with all applicable ADs. Failure to comply with the requirements of an AD causes the certificate of airworthiness of the aircraft to be out of force. Applications for an alternative means of compliance with the requirements of an AD must be made in accordance with CAR Standard 625, Appendix H.
An Airworthiness Directive contains, at a minimum, the following information:
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In accordance with ICAO Circular 95-AN/78 Transport Canada ADs are also distributed to the airworthiness authorities of foreign states (in the SIGS module) where Canadian certified products are believed to be operating.
There are other optional entities in the Special Interest Groups module (SIGS) to which ADs are forwarded, depending upon the circumstances