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/51 Cabin Differential Pressure Limitations 10/73 Applicability: All model 690A with S/Nos. 11102 to 11107 and 11109 to 11116 not modified in accordance with SL No. 270. Document: Aero Commander SB No. 125. Effective: 16 October 1973.