COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Gulfstream (Grumman) G1159 and G-IV Series Aeroplanes AD/G1159/14 Hydraulic Power Shut-Off - Modification 1/75 Applicability: All models with S/Nos. 1 to 153 and 775. Document: Grumman Aircraft Service Change No. 186. Compliance: Within 150 hours time in service after 31 January 1975.