{"id":"F2006B04674","name":"AD/BELL 412/4 Amdt 1 - Main Rotor Yoke - Inspection, Retirement and Modification","slug":"ad-bell-412-4-amdt-1-main-rotor-yoke-inspection-retirement-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44426,"registerId":"commonwealth-F2006B04674-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 412/4 Amdt 1 - Main Rotor Yoke - Inspection, Retirement and Modification","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)  Bell Helicopter Textron 412 Series Helicopters\n\n \n\nAD/BELL 412/4\n\nAmdt 1\n\n\nMain Rotor Yoke - Inspection, Retirement and Modification\n\n\n2/83\n\n \n\nApplicability: As specified in requirement documents.\n\n \n\nDocument: Bell Alert Service Bulletin No. 412-82-6; and Bell Alert Service Bulletin No. 412-82-8; and Bell Alert Service Bulletin No. 412-82-9.\n\n \n\nCompliance: As specified in requirement documents.\n\n \n\nBackground:  This Directive follows action recommended by the manufacturer relating to cracking of the main rotor titanium yoke.\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":4,"scope_assessment":{"changed":false,"description":"The AD implements the manufacturer's recommended actions to address cracking of the main rotor titanium yoke by making compliance with the specified Bell Alert Service Bulletins mandatory. The AD does not itself expand or narrow technical scope; instead it incorporates the scope and procedures set out in the referenced requirement documents (Background; Document; Compliance)."},"complexity_factors":["Reliance on external requirement documents for all technical and applicability details (Applicability: \"As specified in requirement documents\"; Document: Bell Alert Service Bulletins; Compliance: \"As specified in requirement documents\").","Technical nature of tasks (inspection, retirement and modification of a main rotor titanium yoke) requiring specialist maintenance skills and possibly non-routine parts (Title: \"Main Rotor Yoke - Inspection, Retirement and Modification\").","Multiple service bulletins referenced rather than a single consolidated technical instruction (Document: Nos. 412-82-6, -82-8, -82-9).","Absence of explicit timelines, criteria or costs in the AD itself — those are left to the service bulletins, increasing the need to consult external materials (Compliance: \"As specified in requirement documents\").","Regulatory embedding under Civil Aviation Regulations, Part 39, which creates mandatory legal effect while leaving technical detail to manufacturer documents (header: \"Civil Aviation Regulations 1998, PART 39\")."],"plain_english_summary":"This Airworthiness Directive makes manufacturer-recommended inspections, retirement criteria and modifications for the main-rotor titanium yoke mandatory for Australian-registered Bell 412 helicopters by requiring compliance with the referenced Bell Alert Service Bulletins. It affects owners, operators and maintenance organisations, who must obtain and follow those bulletins, schedule the work, and bear the costs. CASA enforces the AD under Part 39 of the Civil Aviation Regulations."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow airworthiness directive focused on a specific mechanical defect in a specific helicopter model. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (under 300 words)","No defined terms section — relies entirely on external manufacturer documents","No conditional logic or nested exceptions in the text itself","Simple structure: applicability, document reference, compliance, background","All technical complexity is outsourced to referenced Bell Service Bulletins (not contained in this legislative instrument)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to **Bell 412 series helicopters**.\n\n**What it does:**\n- Requires owners and operators to inspect, retire (take out of service), or modify the **main rotor yoke** — a critical titanium component that connects the rotor blades to the helicopter.\n- The directive was issued because the manufacturer (Bell) found **cracking** in these yokes, which could lead to catastrophic rotor failure.\n\n**Who must follow it:**\n- Anyone operating or maintaining Bell 412 helicopters in Australia.\n\n**How to comply:**\n- Follow the specific instructions in three Bell Alert Service Bulletins (technical notices from the manufacturer):\n  - 412-82-6\n  - 412-82-8  \n  - 412-82-9\n\n**Why it matters:**\nMain rotor yoke failure would cause the helicopter to lose lift and crash. This AD prevents that by forcing operators to check for cracks and replace or fix parts before they fail."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-412-4-amdt-1-main-rotor-yoke-inspection-retirement-and-modification","history":"/api/acts/ad-bell-412-4-amdt-1-main-rotor-yoke-inspection-retirement-and-modification/history","analysis":"/api/acts/ad-bell-412-4-amdt-1-main-rotor-yoke-inspection-retirement-and-modification/analysis","conflicts":"/api/acts/ad-bell-412-4-amdt-1-main-rotor-yoke-inspection-retirement-and-modification/conflicts","importantCases":"/api/acts/ad-bell-412-4-amdt-1-main-rotor-yoke-inspection-retirement-and-modification/important-cases","documents":"/api/acts/ad-bell-412-4-amdt-1-main-rotor-yoke-inspection-retirement-and-modification/documents"}}