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-6/35 Amdt 2 Wing Rear Spar Attachment Fittings 3/92 Applicability: Model DHC-6, all series, with serial numbers 1 through 330 inclusive, not incorporating modification 6/1301 or 6/1630. Requirement: 1. Action in accordance with de Havilland Service Bulletin 6/295 Revision B; subject to the following changes: (a) Inspection Method A.1 (Radiographic) is to have the exposure time of 60 seconds increased to 120 seconds for the inboard X-ray tube location; and (b) The X-ray beam angle of approximately 10 degrees is to be changed to approximately 5 degrees for all of the X-ray locations. 2. Incorporate de Havilland modification 6/1301. Note: Transport Canada AD CF-73-03 R1 refers. Compliance: 1. At intervals specified in the Requirement Document, until modified in accordance with Requirement 2. 2. Prior to 30 September 1993. The compliance with paragraphs of the previous issue of this Directive were: For Paragraph 1 - Within 200 hours time in service after 20 October 1972 and thereafter at intervals not exceeding 200 hours time in service. For Paragraph 2 to 6 - Within the time limits as detailed in the respective paragraphs. This Amendment is effective from 6 March 1992. Background: Inter-rivet cracking of the top flange of the attachment cap member, part number C6WM1032-1 and -2 located at the inboard end of the wing rear spar, has been found on a number of aircraft in service. Reports have also been received that the radiographic inspection set out in the de Havilland Service Bulletin 6/295 is not locating all the cracks. Amendment 2 is issued to align this Directive with a revision of the related Country of Origin AD, which requires terminating action in lieu of ongoing inspections.