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-6/30 Anti-Reverse System - Modification 11/70 Applicability: All model PC-6/B1-H2 with S/Nos prior to 726. Requirement: 1. Modify anti-reversing circuit as per para 2.21 of Pilatus SB No. 101. 2. Test anti-reversing valve as per para 2.1 of Pilatus SN No. 101. 3. Function test anti-reversing system as per para 2.22 of Pilatus SB No. 101. Compliance: For Para. 1 - within 100 hours time in service after 31 December 1970. For Paras. 2 and 3 - Within 100 hours time in service after 31 December 1970 and thereafter at intervals not exceeding 100 hours time in service.