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-600/20 ADG Output Harness Chafing 8/91 DM Applicability: All CL-600 aircraft as specified in the Requirement Documents. Requirement: 1. Action in accordance with Part A of Canadair Service Bulletin A600-0612 or A601-0370 as applicable. 2. Action in accordance with Part B of Canadair Service Bulletin A600-0612 or A601-0370 as applicable. Compliance: For Requirement 1. Within 25 hours time in service after 13 June1991. For Requirement 2. Within 600 hours time in service after 13 June 1991. Background: Three instances of the ADG electrical output harness being chafed through whilst in the stowed position have been reported. When deployed, the chafed wires short circuited to structure, and resulted in the ADG being unable to provide electrical power to the essential bus when required. Damage to the output harness and its supporting structure also resulted.