AIRWORTHINESS DIRECTIVE On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/CL-600/80 and issues the following 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. Bombardier (Canadair) CL-600 (Challenger) Series Aeroplanes AD/CL-600/80 Amdt 1 Air Supply Duct Flanges 10/2009 Applicability: Bombardier Inc. Model CL-600-2B19 aircraft, serial number 7003 through 7477. Requirement: Action in accordance with Transport Canada AD CF-2003-05R2. Compliance: As detailed in Transport Canada AD CF-2003-05R2 with a revised effective date of 24 September 2009. This Amendment becomes effective on 24 September 2009. Background: The manufacturing procedure used to attach the flanges to the air supply ducts has resulted in bonds that may lose shear strength at elevated temperatures. This condition could potentially cause the duct to disconnect and in combination with the failure of a bulkhead check valve, result in the in-flight loss of aircraft pressurization. Part A of Transport Canada, mandated by the original issue of this AD has been superseded by Transport Canada AD 2009-31. This AD retains the remaining parts of Transport Canada AD 2003-05R1. The original issue of this AD became effective on 30 August 2007. James Coyne Delegate of the Civil Aviation Safety Authority 14 August 2009