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 39.1 (1) of CAR 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. Boeing 737 Series Aeroplanes AD/B737/203 Pressure Fuelling System 2/2003 Applicability: Model 737-600, -700, -700C, -800 and -900 series aeroplanes, as listed in Boeing Alert Service Bulletin (ASB) 737-28A1142, Revision 2, dated 26 November 2002. Requirement: Replace the existing fuelling float switch and conduit assemblies in the main and centre fuel tanks with new, improved assemblies (includes a new float switch and a new conduit assembly with a liner system inside the conduit), in accordance with Work Packages I and II of the Accomplishment Instructions of Boeing ASB 737- 28A1142, Revision 2. Replacements carried out before the effective date of this Directive in accordance with Boeing ASB 737-28A1142, dated 7 February 2002, are considered acceptable for compliance with this Directive. Note 1: Due to the lack of sleeving on the existing electrical wire installations of the centre fuel tank, it is recommended that Work Package II be completed before Work Package I. Note 2: FAA AD 2002-26-18 Amdt 39-13006 refers. Compliance: For aeroplanes that have accumulated fewer than 5,000 total hours time in service (TIS) as of the effective date of this Directive - Within 2 years after the effective date of this Directive. For aeroplanes that have accumulated 5,000 total hours TIS or more, but fewer than 10,000 total hours TIS as of the effective date of this Directive - Within 1 year after the effective date of this Directive. For aeroplanes that have accumulated 10,000 total hours TIS or more as of the effective date of this Directive - Within 180 days after the effective date of this Directive. This Airworthiness Directive becomes effective on 20 February 2003. Boeing 737 Series Aeroplanes AD/B737/203 (continued) Background: This Directive requires replacement of the existing fuelling float switch and conduit assemblies in the main and centre fuel tanks with new, improved assemblies. These actions are intended to prevent fluid contamination inside the fuelling float switch or chafing of the wiring to the in-tank conduit, which could generate an ignition source and consequent fire and explosion in the fuel tank. Neville James Probert Delegate of the Civil Aviation Safety Authority 9 January 2003 The above AD is notified in the Commonwealth of Australia Gazette on 29 January 2003.