COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 310 Series Aeroplanes AD/CESSNA 310/30 Alternate Air System - Modification 7/73 Applicability: Model 310 with S/Nos. 310N0001 to 310Q0520 but excluding model T310. Document: Cessna SL No. ME72-21. Compliance: Within 100 hours time in service after 31 July 1973.