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-6/18 Horizontal Stabiliser Tip Plates - Modification N/K Applicability: All models with S/Nos. 514, 523, 530, 531, 534, 547, 551, 552, 557 and 563. Document: Pilatus SB No. 71. Compliance: Before 2 November 1967.