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-6/24 Amdt 3 Elevator and Tailplane 9/94 Applicability: All model DHC-6 aircraft. Requirement: 1. Accomplish the inspections defined in the Accomplishment Instructions in de Havilland Service Bulletin 6/421 Revision B. 2. Install Modification 6/1799 in accordance with de Havilland Service Bulletin 6/421 Revision B. Note 1: Incorporation of Modification 6/1799 provides terminating action for the inspection requirements of this Directive. Note 2: Transport Canada AD CF-83-11R1 refers. Compliance: 1. Within 50 hours time in service after 31 August 1983, and thereafter at intervals not to exceed 1200 hours time in service. 2. Unless already accomplished, prior to 31 March 1995. The compliance of the previous issue of this Directive remains unchanged as Requirement 1, while Requirement 2 is introduced in this issue. This amendment is effective from 18 August 1994. Background: There have been reported instances of cracking, galling, and enlargement of bolt holes in the elevator outboard hinge assemblies, a lug failure on the tailplane fitting, and elongated holes in the elevator attachment fitting at the attachment to the hinge arm assembly. Amendment 2 relaxed the repeat inspection interval. Amendment 3 is issued to align this Directive with a revision of the related Transport Canada AD which requires modification action pursuant to Transport Canada's Ageing Aircraft Program.