COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 767 Series Aeroplanes AD/B767/6 Flying Controls Self Locking Nuts 12/85 TX Applicability: All Model 767 with line position 2 to 121, and 124 to 126. Requirement: Action in accordance with: 1. Boeing Alert Service Bulletin 767-27A0064. 2. (FAA ADT85-21-51 Paras. A and B refer). Compliance: As detailed in Requirement Document No. 2. Background: The manufacturer has advised that two incidents of defective self-locking nuts found in the primary flight control system (horizontal stabilizer) have been reported. The same type of nut is also used in the secondary flight control system - trailing edge flap and spoiler. These reports indicate that the self-locking nuts have backed off which could cause the disconnection of actuators from control surfaces and result in complete or partial loss of control of the aircraft.