COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Fokker F100 (F28 Mk 100) Series Aeroplanes AD/F100/31 Flight Augmentation Computer Replacement 4/99 Applicability: Model F.28 Mk.0100 aeroplanes serial numbers 11244 through 11348 inclusive. Requirement: 1. Unless previously accomplished replace all Collins Flight Augmentation Computer (FAC) units, part number (P/N) 622-7478-321, with modified units P/N 622-7478- 401 Mod.11 in accordance with Fokker Service Bulletin (SB) F100-22-026 dated 1 July 1991. 2. Replace all Collins FAC units, P/N 622-7478-401, with modified units P/N 622-7478-401 Mod.11 in accordance with Fokker SB F100-22-032 dated 2 September 1991. Note: Netherlands AD 1991-057/4 refers. Compliance: 1. Prior to 22 December 1999. 2. Prior to 22 December 1999. This Airworthiness Directive becomes effective on 22 April 1999. Background: The modified computers provide improved fault isolation to allow cross comparison of more signals than previously possible. Problems with stabiliser trim systems during ground testing and nuisance yaw-damper faults during take off have been solved by the incorporation of an additional modification.