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-6/22 Wing Fixed Spoilers - Installation 12/67 Applicability: All models prior to S/No. 656. Document: Pilatus SB No. 76. Compliance: Before 1 April 1968.