COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES De Havilland DHC-1 (Chipmunk) Series Aeroplanes AD/DHC-1/38 Re-Classification of Existing Modifications to Mandatory Status Applicability: All DHC-1 Chipmunk aircraft. 7/97 Requirement: Action in accordance with British Aerospace Mandatory Technical News Sheet (TNS) CT (C1) No. 200. Note 1: TNS CT (C1) No.200 also informs operators how to determine that the required modifications have been incorporated on their aircraft. Note 2: UK CAA AD 006-03-97 refers. Compliance: Unless already accomplished, before 19 September 1997. This airworthiness directive becomes effective on 19 June 1997. Background: The UK CAA requires that certain modifications be incorporated, in order to ensure the continued airworthiness of Chipmunk aircraft.