COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Gates Learjet 24 & 25 Series Aeroplanes AD/LEARJET/4 Tip Tank Fuel Pressure Relief - Modification 9/73 Applicability: Model 24 with S/no. 24-218 and 24-230 to 24-269, Model 25 with S/no. 25-061, 25- 064 and 25-070 to 25-124. Document: Modification Kit No. AMK 73-2. Compliance: Within 100 hours time in service after 28 September 1973.