COMMONWEALTH OF AUSTRALIA CIVIL AVIATION ORDERS CIVIL AVIATION SAFETY AUTHORITY PART 105 SCHEDULE OF AIRWORTHINESS DIRECTIVES GULFSTREAM (GRUMMAN) G.159 SERIES AEROPLANES AD/G159/9 Lower Centre Section Skin - Inspection 12/67 Applicability: All models. Requirement: Remove the lower centre section fairings P/Ns 159 W10400-121 and 159-W10401- 121 and inspect the wing planks for corrosion. If corrosion is found, repair the wingplanks in accordance with a scheme approved by the Secretary before further flight. Compliance: Before 1 April 1967 and thereafter at intervals not exceeding 6 months.