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-6/4 Aileron Balance Weight Arm - Inspection 3/66 Applicability: All models with S/Nos. 338, 341, 344, 345, 349, 350, 516 to 518, 521, 522, 524, 525, 526, 528, 531, 532, 535 to 538, 543 to 551 and 554. Document: Pilatus SB No. 25. Compliance: At intervals not exceeding 100 hours time in service after 15 April 1966.