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. Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes AD/DHC-8/147 Main Landing Gear 7/2009 Airworthiness Limitation Items Applicability: DHC-8 Aircraft, Models 400, 401 and 402, serial numbers 4001, 4003, 4004, 4006 and 4008 through 4227. Requirement: Action in accordance with the requirements of Transport Canada AD CF-2009-17. Compliance: As specified in the Requirement document, with a revised effective date of 2 July 2009. This Airworthiness Directive becomes effective on 2 July 2009. Background: Certain main landing gear components have prematurely failed during certification testing. The DHC-8-400 Maintenance Requirements Manual, Airworthiness Limitations Items, has been revised to incorporate the revised safe life limits for the main landing gear lock actuator assembly, retraction actuator assembly rod end and piston, and the upper bearing in the main landing gear shock strut assembly. Failure of these components could adversely affect the structural integrity of the main landing gear. David Villiers Delegate of the Civil Aviation Safety Authority 19 May 2009