{"id":"F2006B03061","name":"AD/B747/159 - Forward Pressure Bulkhead","slug":"ad-b747-159-forward-pressure-bulkhead","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42420,"registerId":"commonwealth-F2006B03061-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/159 - Forward Pressure Bulkhead","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBoeing 747 Series Aeroplanes\n\nAD/B747/159 Forward Pressure Bulkhead 8/96\n\nApplicability: All model 747s, line numbers 1 to 886 excepting 80, 85 and 151.\n\nRequirement: Inspect the forward pressure bulkhead structure in accordance with Boeing SB 747- 53-2355.\n\nNote: This Service Bulletin supersedes Boeing SB 747-53-2210.\n\nCompliance: 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.\n\nModification or repair of each area in accordance with Boeing SB 747-53-2355 cancels the inspection requirements for that area.\n\nNote: For the purposes of this AD, flights on which the cabin pressure differential does not exceed 2.0 psi need not be counted.\n\nBackground: 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.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This Directive replaces the outer ring chord inspections previously required by AD/B747/46 Amdt 4 and imposes the inspection regime and structural modification/repair pathway set out in Boeing SB 747-53-2355 across the specified 747 fleet; inspection requirements for any area are removed once that area is modified or repaired per the Service Bulletin."},"complexity_factors":["Normative reliance on an external Boeing Service Bulletin (SB 747-53-2355) for inspection intervals and procedures","Flight-counting rule that excludes flights with cabin differential ≤2.0 psi (requires monitoring/recording cabin differential)","Applicability carve-outs limited to specific line numbers (1–886 except 80, 85 and 151)","Compliance timing for overdue aircraft (inspect within 500 flights after 18 July 1996)","Modification or repair per the Service Bulletin cancels inspection requirements for the repaired area (interaction between inspections and repairs)","Supersedes prior AD inspections (replaces outer ring chord inspections from AD/B747/46 Amdt 4)"],"plain_english_summary":"This Airworthiness Directive requires operators of most Boeing 747s (line numbers 1–886, except 80, 85 and 151) to inspect the forward pressure bulkhead using Boeing Service Bulletin 747-53-2355 at the specified flight thresholds and intervals; repairs or modifications done per that Service Bulletin remove the inspection requirement for the repaired area. Flights with cabin differential ≤2.0 psi are excluded from the flight-counting rule.\n\nThe objective claimed is to limit fatigue cracking from repeated pressurisation. Operators pay inspection and repair costs, must track qualifying flights, and follow the technical procedures set out in the Boeing Service Bulletin while CASA enforces the AD."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific structural fatigue issue in Boeing 747 aircraft. The scope remains precisely focused on forward pressure bulkhead inspections as originally intended. The document explicitly states it replaces earlier inspection requirements (AD/B747/46 Amdt 4), indicating this is a refinement rather than scope expansion."},"complexity_factors":["Short, single-purpose directive (approximately 200 words)","Only 3 defined elements: applicability range, compliance threshold, and the 2.0 psi exception","Single cross-reference to Boeing Service Bulletin 747-53-2355 (external technical document)","One conditional exception (flights under 2.0 psi differential excluded from counting)","Clear, linear structure: Applicability → Requirement → Compliance → Background"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of specified Boeing 747s (line numbers 1–886, with listed exceptions) to inspect the forward pressure bulkhead per Boeing Service Bulletin 747-53-2355, meeting prescribed flight-threshold timing (or within 500 flights after 18 July 1996 if thresholds were already exceeded). Flights with cabin differential below 2.0 psi are excluded from counting toward those thresholds.\n\nThe AD responds to fatigue cracks found in the bulkhead and replaces the earlier, narrower AD/B747/46 Amendment 4 to prevent possible structural failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-159-forward-pressure-bulkhead","history":"/api/acts/ad-b747-159-forward-pressure-bulkhead/history","analysis":"/api/acts/ad-b747-159-forward-pressure-bulkhead/analysis","conflicts":"/api/acts/ad-b747-159-forward-pressure-bulkhead/conflicts","importantCases":"/api/acts/ad-b747-159-forward-pressure-bulkhead/important-cases","documents":"/api/acts/ad-b747-159-forward-pressure-bulkhead/documents"}}