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. Boeing 737 Series Aeroplanes AD/B737/296 Auxiliary Fuel System 12/2006 Applicability: Boeing Model 737-200, -300, -400, and -500 series aeroplanes equipped with an auxiliary fuel system installed in accordance with FAA Approved Supplemental Type Certificate (STC) SA83NE, SA1078NE, SA725NE, ST00040NY, or ST01337NY; having serial numbers (S/N) listed in Table 1 of this AD. Table 1 - Applicability For Model - Having S/N(s) - As identified in PATS Aircraft Service Bulletin - 737-200 series airplanes 22431 and 22628 SA83NE-28-SB-002_IR, dated 7 June 7 2006 737-200 series airplanes 22600 SA1078NE-28-SB-005_A, Revision A, dated 21 June 2006 737-200, -300, 23800, 22620, 23124, 23468, 26333, 26307, 27456, 27426, and 27906 SA725NE-28-SB-007_B, Revision B, dated 27 July 2006 -400, and -500 series airplanes 737-500 series airplanes 24970 ST00040NY-28-SB-003_IR, dated 7 June 2006 737-500 series airplanes 28866 ST01337NY-28-SB-002_IR, dated 7 June 2006 Requirement: Action in accordance with FAA AD 2006-18-11 Amendment 39-14750. Compliance: As detailed in FAA AD 2006-18-11 with a revised effective date of 23 November 2006. This Airworthiness Directive becomes effective on 23 November 2006. Background: This AD results from a re-evaluation of the floor structure and cargo barriers conducted by the STC holder. The actions detailed in this AD are intended to prevent structural overload of the auxiliary fuel tank support structure, which could cause the floor beams to fail and resultant damage to the primary flight controls and the auxiliary power unit fuel lines that pass through the floor beams, and consequent loss of control of the aeroplane. These actions are also intended to prevent structural overload of the cargo barriers, which could cause the barriers to fail, allowing the cargo to shift, resulting in possible damage to the auxiliary fuel tanks, residual fuel leakage, and consequent increased risk of a fire. James Coyne Delegate of the Civil Aviation Safety Authority 12 October 2006