COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 767 Series Aeroplanes AD/B767/58 Left Hydraulic System 9/91 Applicability: Boeing 767 series Aeroplanes as listed in Boeing Alert Service Bulletin 767- 29A0038, dated 3 August 1989. Requirement: Action in accordance with the Technical Requirements of FAA AD 91-12-16. Note: FAA AD 91-12-16 refers to Boeing Alert Service Bulletin 767-29A0038, Amendment 39-7028. Compliance: Required within 3600 hours time-in-service or 24 months from the issue date of this AD, whichever occurs later. Background: FAA AD action was prompted by review and analysis of the B767 flight control system functional redundancy as it relates to the ability of the aeroplane to continue safe flight and landing after structural failure. This condition, if not corrected, could result in loss of controllability of the aeroplane if, following a single event of structural failure, damage occurs to all three hydraulic systems.