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-6/17 Landing Gear Strut - Modification N/K Applicability: All models prior to S/No. 570. Document: Pilatus SB No. 35. Compliance: Before 2 November 1967.