COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bombardier (Canadair) CL-600 (Challenger) Series Aeroplanes AD/CL-600/21 Amdt 2 Tail Cone Fuel Tank 9/93 Applicability: All CL-600-2A12 and CL-600-2B16 aircraft equipped with a tail cone fuel tank. Requirement: Action in accordance with the requirements of Transport Canada Airworthiness Directive CF-91-22R3 dated 27 May 1993. Note: Canadair Alert Service Bulletin A601-0381 Revision No 2 dated 27 January 1992 and Canadair Kit Drawing K601-62011 Issue B refer. Compliance: The Compliance for the previous issue of this Directive was "as directed in the Requirement Document with a revised effective date of 30 June 1992". The compliance for this issue is prior to 31 December 1993. Background: During maintenance in the aft equipment bay the level control valve sensing line, which runs through the aft equipment bay for the tail cone fuel tank, has been broken. Amendment 1 required a modification to the tail cone fuel tank level control valve sensing line which provided terminating action for the repetitive inspection requirement. This amendment requires the installation of a bonding jumper assembly to remove the threat of an explosion following a lightning strike.