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-6/16 Amdt 5 Wing Front Spar Attachment Fittings 3/87 Applicability: All models with serial numbers 1 to 210 inclusive. Requirement: Action in accordance with de Havilland of Canada Service Bulletin No 6/174 Revision D, Part A or Part B as applicable. Compliance: For Part A of SB 6/174: At intervals not exceeding 500 hours time in service or 3 months, whichever occurs first. For Part B of SB 6/174: Within 100 hours time in service after 31 July 1974, unless already accomplished. Note: The repetitive inspections of Part A may be discontinued upon installation of unused de Havilland fittings P/N C6WM 1133-1 and -2. Background: Stress corrosion cracks have been found in service. The Service Bulletin requires inspection of the fittings and re- torquing of the wing attach bolts. This revision implements Revision D to the SB. Canadian AD's CF-69-4, CF-69-5 and CF-76-08 refer.