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 747 Series Aeroplanes AD/B747/357 Station 400 Upper Deck Floor Beam 8/2007 Applicability: Model 747-400 series aircraft, as identified in Boeing Alert Service Bulletin 747-53A2660, dated 16 November 2006, or later FAA approved revision. Requirement: Action in accordance with the technical requirements of FAA AD 2007-10-09 Amdt 39-15050. Compliance: As specified in the Requirement document, with a revised effective date of 2 August 2007. This Airworthiness Directive becomes effective on 2 August 2007. Background: The FAA received several reports of fatigue cracking in upper deck floor beams made from 7000 series aluminium alloy. Undetected cracking in the upper deck floor beam at station 400 could extend and sever the floor beam, which could result in loss of controllability and rapid decompression of the aircraft. David Villiers Delegate of the Civil Aviation Safety Authority 19 June 2007