{"id":"F2006B03229","name":"AD/B747/49 - Vertical Fin Access Cover Installation","slug":"ad-b747-49-vertical-fin-access-cover-installation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42627,"registerId":"commonwealth-F2006B03229-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/49 - Vertical Fin Access Cover Installation","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/B747/49 Vertical Fin Access Cover Installation 6/86\n\nApplicability: All models with line numbers to 625.\n\n \n\nRequirement: Action in accordance with Boeing SB 747-53A2264.\n\n \n\nNote: FAA AD 86-08-02 refers.\n\n \n\nCompliance: Prior to 30 November 1986.\n\n \n\nBackground: The FAA has determined that the vertical fin could be over pressurised to the point of structural failure in the event of failure of the aft pressure bulkhead.\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\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive issued in 1986 with a specific technical purpose. It has not expanded beyond its original scope — it remains a single-issue airworthiness requirement for a specific aircraft type and manufacturing batch."},"complexity_factors":["Extremely short document — only 8 substantive lines of regulatory text","No defined terms section — all language is plain technical aviation terminology","Single, unambiguous compliance requirement (follow the Boeing service bulletin)","No cross-references to other legislation beyond a single note about the related FAA directive","No conditional logic, exceptions, or nested provisions","Clear applicability criteria (line numbers to 625) with no ambiguity"],"plain_english_summary":"**What this is:** 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:** It orders owners and operators of certain Boeing 747 aeroplanes to install an access cover on the vertical fin (the tall tail section of the plane). This modification must be done following Boeing's official service bulletin (SB 747-53A2264).\n\n**Who it affects:** All Boeing 747 models with \"line numbers\" (manufacturing serial numbers) up to 625 — essentially, the earlier production aircraft in this series.\n\n**Why it matters:** The US Federal Aviation Administration (FAA) discovered a serious safety risk. If the aft pressure bulkhead (a critical wall at the rear of the passenger cabin that maintains cabin pressure) fails, it could cause the vertical fin to become dangerously over-pressurised. This over-pressurisation could lead to **structural failure of the tail** — a potentially catastrophic event. The access cover installation prevents this dangerous pressure buildup.\n\n**Deadline:** The work had to be completed before 30 November 1986."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive’s stated scope and remedy are consistent within the text: it applies to Boeing 747s up to line 625 and requires installation per Boeing SB 747-53A2264 by the stated date to address the FAA-identified over-pressurisation risk in the vertical fin. The instrument does not indicate any expansion or narrowing of scope from the stated safety concern; it sets a single, specific compliance requirement tied to the manufacturer’s service bulletin. (Applicability; Requirement; Compliance; Background)"},"complexity_factors":["Single, time-limited requirement (clear deadline and single referenced action). (Compliance; Requirement)","Narrow applicability (only Boeing 747s with line numbers to 625). (Applicability)","Dependence on an external technical document (Boeing SB 747-53A2264) for implementation details. (Requirement)","No alternative compliance pathways or exemptions set out in the text—implementation depends on operators and maintenance organisations. (Requirement)","No technical data, cost estimates or enforcement mechanisms included in this text, which shifts complexity to operational implementation rather than legal interpretation. (Requirement; Compliance)"],"plain_english_summary":"Operators of Boeing 747s with line numbers up to 625 must install a vertical fin access cover per Boeing Service Bulletin 747-53A2264 by 30 November 1986.  \n\nThe AD mandates this modification because the FAA found that a failed aft pressure bulkhead could over‑pressurise and risk structural failure of the vertical fin; owners/operators bear the cost and scheduling of the work."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-49-vertical-fin-access-cover-installation","history":"/api/acts/ad-b747-49-vertical-fin-access-cover-installation/history","analysis":"/api/acts/ad-b747-49-vertical-fin-access-cover-installation/analysis","conflicts":"/api/acts/ad-b747-49-vertical-fin-access-cover-installation/conflicts","importantCases":"/api/acts/ad-b747-49-vertical-fin-access-cover-installation/important-cases","documents":"/api/acts/ad-b747-49-vertical-fin-access-cover-installation/documents"}}