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. Dornier 328 Series Aeroplanes AD/DO 328/55 APU Fire Extinguisher Cartridge 4/2006 Applicability: Dornier 328-100 aeroplanes fitted with an Auxiliary Power Unit (APU). Requirement: Replace the existing cartridge with an improved version as detailed in Dornier 328 Service Bulletin No. SB-328-26-342 dated 2 November 2000 or later LBA approved revisions. Note: LBA AD 2001-292 refers. Compliance: Within 30 days after the effective date of this AD unless previously accomplished. This Airworthiness Directive becomes effective on 13 April 2006. Background: The improved APU fire cartridge provides a greater margin of safety and rupture disc opening efficiency. James Coyne Delegate of the Civil Aviation Safety Authority 3 March 2006