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/64 Fatigue Life Limitation - Pressurised Fuselage 6/77 Applicability: Models 680T, 680V, 680W, 680FL(P), 681, 685, 690, 690A and 690B. Requirement: Retire the pressure hull and related structure from service. Compliance: For models 680T, 680V, 680W, 680FL(P), 681 and 690: On or before achieving 7500 pressurised flight cycles. For models 685, 690a and 690B: On or before 10,000 pressurised flight cycles.