COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 185 Series Aeroplanes AD/CESSNA 185/21 Engine Air Inlet Duct 5/74 Applicability: All model A185 with S/Nos. 18502008 to 18502650. Requirement: Action in accordance with Cessna SL No. SE75-5. Note: FAA AD 75-09-06 refers. Compliance: Within 500 hours time in service after 12 May 1975.