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-6/43 Amdt 1 Elevator Housing Assembly Lower Mounting Structure 9/91 Applicability: Model DHC-6 with serial numbers 2 through 494, 497 through 503, 505 and 507. Requirement: Action in accordance with the Technical Requirements of Transport Canada AD CF- 77-05 R1. Note: De Havilland SB 6/348 refers. Compliance: As specified in the Requirement Document. Background: This amendment is raised to reflect transport Canada's ageing aircraft program, which requires terminating action rather than repetitive inspections for known critical service problems.