COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/56 Fuselage - Tail Section Structure 2/87 Applicability: All models with line numbers 001 to 554. Requirement: Action in accordance with Boeing SB 747-53-2220 R2. Note: FAA AD 86-16-05 refers. Compliance: As per Requirement Document. Background: The manufacturer reports instances of in-flight cabin pressure loss due to aft pressure bulkhead corrosion or deterioration of the composite Auxiliary Power Unit (APU) duct pressure pan.