COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Ayres Thrush (Snow) Commander Series Aeroplanes AD/AC-SNOW/11 Carburettor Air Selector Valve Assembly - Inspection Applicability: Model S-2R with S/Nos. 5000 and up. Document: Rockwell International SB No. SB-AG-8. 3/78 Compliance: Within 50 hours' time in service after 30 April 1978 and thereafter at intervals not exceeding 50 hours' time in service.