COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES DHC-6 (Twin Otter) Series Aeroplanes AD/DHC-6/65 Wing Strut Chafing 4/92 Applicability: All models. Requirement: Inspect for the presence of the protective nylon shield incorporated in the wing strut upper fairings by de Havilland Modification 6/1581. If the shield is not installed, visually inspect the struts for damage in accordance with de Havilland Service Bulletin 6/342, and incorporate Modification 6/1581. Note: Transport Canada Airworthiness Directive CF-91-30 dated 8 August 1991 refers. Compliance: 1. Inspect within 25 hours time in service after 2 April 1992. 2. Modify before 25 June 1992. Background: Transport Canada's aging aircraft review identified this as mandatory action.