COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/159 Forward Pressure Bulkhead 8/96 Applicability: All model 747s, line numbers 1 to 886 excepting 80, 85 and 151. Requirement: Inspect the forward pressure bulkhead structure in accordance with Boeing SB 747- 53-2355. Note: This Service Bulletin supersedes Boeing SB 747-53-2210. Compliance: Inspect at the flight thresholds and intervals specified in Boeing SB 747-53-2355, Paragraph D. Aircraft over these times must be inspected within 500 flights after 18 July 1996. Modification or repair of each area in accordance with Boeing SB 747-53-2355 cancels the inspection requirements for that area. Note: For the purposes of this AD, flights on which the cabin pressure differential does not exceed 2.0 psi need not be counted. Background: Numerous cracks caused by cyclic pressure loads have been found in the forward pressure bulkhead on aircraft in service and on both the 747 forward fuselage fatigue test articles. A series of inspections and structural changes are required to limit the fatigue damage to the bulkhead. This Directive replaces outer ring chord inspections previously specified in AD/B747/46 Amdt 4.