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-6/45 Amdt 1 Fuselage Side Frames Stns 218.125 and 219.525 4/92 Applicability: Model DHC-6 Series with serial numbers 1 through 411 inclusive. Requirement: 1. Action in accordance with de Havilland SB 6/371. 2. Incorporate de Havilland modifications 6/1461 (or 6/1553) and 6/1462. Note: Transport Canada AD CF-78-17 R1 refers. Compliance: 1. At intervals as specified in the requirement document, until modified in accordance with Requirement 2. 2. Prior to 1 January 1996. The compliance of the previous issue of this Directive was as per Requirement Document. This amendment is effective from 2 April 1992. Background: Inter-rivet cracking of the fuselage side frame skin flanges at Stations 218.125 and 219.525 has occurred on a number of aircraft in service. Cracks are initiated by stress induced by riveting; side frames of material with improved stress corrosion resistance have been introduced by the manufacturer. Amendment 1 is issued to align this Directive with a revision of the relevant Country of Origin AD which requires terminating action in lieu of on going repetitive inspections.