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/B747/351 Engine Pylon Internal Structure 10/2006 Applicability: Model 747-200B, -200C, -200F, -300, and 747SR series aircraft; as identified in Boeing Special Attention Service Bulletin 747-54-2223 original issue, or later FAA approved revision. Requirement: Action in accordance with the technical requirements of FAA AD 2006-16-10 Amdt 39-14710. Compliance: As specified in the Requirement document, with a revised effective date of 28 September 2006. This Airworthiness Directive becomes effective on 28 September 2006. Background: The FAA received reports of heat damage and cracking of the skin and internal structure adjacent to and aft of the pre-cooler exhaust vent on several engine struts. Undetected cracking, buckling, wrinkling, or heat damage of the skin and internal structure of the engine struts could result in extensive damage to the engine struts, and consequent possible in-flight separation of an affected engine. David Villiers Delegate of the Civil Aviation Safety Authority 17 August 2006