COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Piper PA-23 (Apache and Aztec) Series Aeroplanes AD/PA-23/63 Heater Fuel Valve - Inspection 7/74 Applicability: Models PA23-150 and PA23-160 with S/Nos. 23-1 to 23-2046, Models PA23-235 and PA23-250 with S/Nos. 27-1 to 27-3836, 27-3838 to 27-3943. Document: Piper SB No. 401. Compliance: Within 100 hours time in service after 31 July 1974.