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-6/63 Gust Lock Assembly 3/90 DM Applicability: S/Nos 1 to 690, 692, 693, 695 and 696. Requirement: Action in accordance with Boeing Canada SB 6/508. Note: Canadian AD CF-90-01 refers. Compliance: Prior to 31 July 1990. Background: Three instances have been reported where aircraft took off with pre-mod 6/1676 gust locks still engaged.