COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Pilatus Porter PC-6 Series Aeroplanes AD/PC-6/31 Wing Strut Internal Corrosion - Inspection 7/71 Applicability: All models except Fairchild Hiller production. Document: Pilatus SB No. 105. Compliance: Within 100 hours time in service after 31 August 1971 and thereafter at intervals not exceeding 100 hours time in service.