COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/99 Differential Protection Current Transformers - Wiring Applicability: As specified in the requirement document. Requirement: Action in accordance with the Boeing Service Bulletin 747-24-2154. Note: FAA AD 91-18-05 also refers. Compliance: Prior to 18 March 1992. 12/91 Background: This AD is issued following a 747 Safety Assessment which demonstrated that the potential exists for a single fault to cause the loss of all normal sources of aircraft power. Compliance with this AD requires re-routing and adding shielded wiring associated with the differential protection current transformers in the P6 panel.