AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section. Fokker F100 (F28 Mk 100) Series Aeroplanes AD/F100/78 NLG Door Uplock Bracket Assembly 5/2006 Applicability: Model F.28 Mk. 0070 and Mk. 0100 aircraft, all serial numbers. Requirement: Modify the Nose Landing Gear Door Uplock Bracket Assembly in accordance with the Accomplishment Instructions of Fokker Service Bulletin SBF100-32-143, dated 15 February 2006, or later EASA approved revision. Note: CAA-NL AD NL-2006-004 refers. Compliance: Within 4,000 flight hours after 11 May 2006. This Airworthiness Directive becomes effective on 11 May 2006. Background: Two events have been reported of Fokker 100 aircraft, where the nose landing gear failed to extend in normal mode and problems in opening the nose landing gear doors were experienced, almost preventing extension in emergency (alternate) mode. Investigation revealed that the friction of the bearing in the roller of the nose landing gear door uplock bracket assembly was high, causing increased resistance in the mechanical system that unlocks the doors. David Villiers Delegate of the Civil Aviation Safety Authority 31 March 2006