COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes AD/DHC-8/52 Brake Valve Shuttle Valve Inspection 6/98 Applicability: DHC-8 Aircraft Serial Numbers 003 through 498. Requirement: Perform inspection and replacement as applicable of brake shuttle valve part number 5084-1 in accordance with manufacturer's Service Bulletin No. A8-32-139, dated 8 October 1997 or Rev A dated 19 December 1997. Note: Transport Canada AD CF-98-05 dated 02 March 1998 refers. Compliance: Within 90 days of the effective date of this directive. This airworthiness directive becomes effective on 21 May 1998. Background: Defective filters inside shuttle valve part number 5084-1 have failed in service causing blockage of a brake valve port and subsequent failure of the brake to release after selection. The defect has been traced to a specific batch of filter fittings which have been installed in a specific range of shuttle valves. The affected shuttle valves are used in the hydraulic systems of the DHC 7 and DHC 8 aircraft models. This directive inspects for, and removes from service, affected shuttle valves in the DHC 8 aircraft.