{"id":"F2006B03237","name":"AD/B747/56 - Fuselage - Tail Section Structure","slug":"ad-b747-56-fuselage-tail-section-structure","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42661,"registerId":"commonwealth-F2006B03237-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/56 - Fuselage - Tail Section Structure","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Boeing 747 Series Aeroplanes\n\n \n\nAD/B747/56 Fuselage - Tail Section Structure 2/87\n\nApplicability: All models with line numbers 001 to 554. Requirement:  Action in accordance with Boeing SB 747-53-2220 R2.\n\nNote: FAA AD 86-16-05 refers.\n\n \n\nCompliance: As per Requirement Document.\n\n \n\nBackground: 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.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The document does not indicate any change in scope from an earlier version; it identifies the affected fleet (line numbers 001–554) and makes compliance with Boeing SB 747-53-2220 R2 mandatory. No modification to applicability or additional areas of coverage are stated in the text supplied."},"complexity_factors":["Directive sets a single mandatory action by reference to an external technical document (Boeing SB 747-53-2220 R2) rather than embedding detailed procedures, which makes the AD administratively simple but technically dependent on the SB.","Clear applicability criterion (line numbers 001–554) reduces ambiguity about which aircraft are covered.","Technical content and implementation complexity are delegated to the Boeing service bulletin; the AD itself contains minimal technical detail.","Cross-reference to an FAA AD adds an additional external source to consult for context or alignment.","Practical compliance complexity depends on the technical and scheduling demands of the referenced SB, which are not reproduced in the AD."],"plain_english_summary":"What this directive does\n\n- This Australian airworthiness directive applies to Boeing 747 aeroplanes with line numbers 001 to 554. (Applicability)\n- It requires operators to carry out the work set out in Boeing Service Bulletin 747-53-2220 Revision 2. (Requirement; Compliance)\n- The directive cross-references a related U.S. requirement (FAA AD 86-16-05). (Note)\n\nWhy the rule exists (official rationale)\n\n- The manufacturer reported cases of in-flight cabin pressure loss linked to corrosion of the aft pressure bulkhead or deterioration of the composite APU duct pressure pan. The directive implements the Boeing service instructions to address that risk. (Background)\n\nHow it works mechanically\n\n- Applicability determines which aircraft are covered: Boeing 747s with specified line numbers. (Applicability)\n- The operative obligation is to follow Boeing SB 747-53-2220 R2; the AD does not reproduce the technical steps but makes compliance with that service bulletin mandatory under the Civil Aviation Regulations. (Requirement; Compliance)\n- Compliance is judged against the Requirement Document (the Boeing service bulletin) and enforced under the airworthiness directive regime. (Compliance)\n\nWho pays, who decides, and what behaviour changes\n\n- Who pays: aircraft operators (owners/airlines) will bear the direct costs of inspections, repairs or replacements ordered by the Boeing service bulletin, because the AD makes those actions mandatory for the applicable fleet. (Requirement; Compliance)\n- Who decides: the regulator issues the directive and specifies the external service bulletin as the required work; operators must implement the specified actions. Any judgment about scheduling, choosing authorised maintenance providers, and documenting compliance is made by the operator within the regulatory framework. (Requirement; Compliance)\n- Behaviour change: operators must inspect and, if necessary, repair or replace affected aft pressure bulkheads or APU duct pressure pans per the Boeing SB to reduce the risk of in-flight cabin pressure loss. (Requirement; Background)\n\nCosts, incentives, trade-offs and risks (practical implementation view)\n\n- Direct cost and resource allocation: operators will incur labour, parts, and aircraft downtime to carry out the SB instructions; the AD converts an optional or recommended manufacturer action into a mandatory regulatory obligation. (Requirement; Compliance)\n- Incentives: complying removes regulatory non‑compliance risk and addresses the safety risk identified by the manufacturer; non‑compliance risks enforcement action and continued exposure to the reported failure mode. (Requirement; Background)\n- Trade-offs and opportunity cost: time and money spent on these inspections/repairs cannot be used for other maintenance or operations; operators must prioritise the mandated work over other discretionary activity. (Requirement; Compliance)\n- Implementation risk and discretion: the directive requires following the Boeing SB but does not itself set alternative technical options; any discretionary choices (timing, approved repair facilities, or configuration-specific decisions) will be made by operators and their approved maintenance organisations within the bounds of the SB and regulatory oversight. (Requirement; Compliance)\n- Effects on private contracting and market interaction: the AD ties a regulatory requirement to a manufacturer service bulletin, which channels operators to technical content from Boeing; operators remain free to contract with approved maintenance providers to perform the work, subject to meeting the SB and regulatory documentation requirements. (Requirement; Compliance; Note)\n\nKey citations from the directive\n\n- Applicability: \"All models with line numbers 001 to 554.\" (Applicability)\n- Requirement: \"Action in accordance with Boeing SB 747-53-2220 R2.\" (Requirement)\n- Compliance: \"As per Requirement Document.\" (Compliance)\n- Background (reason): manufacturer reports of in-flight cabin pressure loss due to aft pressure bulkhead corrosion or deterioration of the composite APU duct pressure pan. (Background)\n- Cross-reference: \"FAA AD 86-16-05 refers.\" (Note)\n"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted airworthiness directive addressing a specific structural defect in a defined aircraft population. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined term implicitly referenced (line numbers)","Single cross-reference to FAA AD 86-16-05 and Boeing SB 747-53-2220 R2","No conditional logic or nested exceptions — straightforward applicability and compliance structure","Standard AD format with clear Applicability/Requirement/Compliance/Background sections"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific repairs or inspections on aircraft.\n\n**What it does:**\nOrders owners and operators of certain Boeing 747 aeroplanes to carry out structural inspections and repairs on the tail section of the fuselage (the rear part of the plane's body). The work must follow a specific Boeing service bulletin (SB 747-53-2220 R2).\n\n**Who it affects:**\nAll Boeing 747 models with \"line numbers\" (manufacturing serial numbers) 001 to 554 — essentially the earlier production aircraft in the 747 family.\n\n**Why it matters:**\nThe manufacturer discovered cases where planes lost cabin pressure during flight because of:\n- Corrosion (rust-like deterioration) in the aft pressure bulkhead (a critical wall at the back of the passenger cabin that helps maintain air pressure), or\n- Deterioration of a composite (non-metal) panel around the APU duct (the exhaust path for the auxiliary power unit, a small engine at the tail).\n\nUncontrolled cabin pressure loss at altitude can be catastrophic, so this directive mandates fixes to prevent structural failures."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-56-fuselage-tail-section-structure","history":"/api/acts/ad-b747-56-fuselage-tail-section-structure/history","analysis":"/api/acts/ad-b747-56-fuselage-tail-section-structure/analysis","conflicts":"/api/acts/ad-b747-56-fuselage-tail-section-structure/conflicts","importantCases":"/api/acts/ad-b747-56-fuselage-tail-section-structure/important-cases","documents":"/api/acts/ad-b747-56-fuselage-tail-section-structure/documents"}}