COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Pilatus PC-12 Series Aeroplanes AD/PC-12/18 Flap Drive Shafts 8/99 Applicability: All Model PC-12 and PC-12/45 aircraft. Requirement: Action in accordance with the Accomplishment Instructions of Pilatus Service Bulletin 27-003, dated March 8, 1999. Note: Swiss FOCA AD HB 99-241 refers. Compliance: Before 12 December 1999, unless already accomplished. This Airworthiness Directive becomes effective on 12 August 1999. Background: Reports were received of corroded inner drive cables of the flap flexible shafts (flap drive shafts). Investigations revealed that moisture from the pressurised cabin can enter the flap drive shafts through the unsealed areas of the flap drive shaft attachments and the shaft casings. This Directive requires replacement of the flap inboard and outboard flap drive shafts with modified shafts, the installation of additional gaskets on both sides of the Power Drive Unit, and modification of support brackets.