COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes AD/AC/4 Main Landing Gear Upper NK Retaining Pins - Replacement Applicability: Models 560A, 560E and 680: S/Nos. 231 to 559. Document: 1. Aero Commander SB No. 43; or 2. FAA AD 57-15-1. Compliance: Forthwith.