{"id":"F2006B04351","name":"AD/BELL 204/7 - Tail Rotor Yoke - Inspection","slug":"ad-bell-204-7-tail-rotor-yoke-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44165,"registerId":"commonwealth-F2006B04351-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 204/7 - Tail Rotor Yoke - Inspection","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 204 Series Helicopters\n\n \n\nAD/BELL 204/7 Tail Rotor Yoke - Inspection NK\n\nApplicability: All 204B models fitted with tail rotor yoke P/N 204-010-781-9 or 204-010-781-5.\n\n \n\nRequirement: Inspect yoke assembly P/N 204-010-781-5 or 204-010-781-9 by magnetic particle method with particular emphasis on the threaded portion of the yoke spindle.\n\nMaximum amperage 1400 amps. DC or 1100 amps. AC. Do not exceed 4200 ampere turns.\n\n \n\nCompliance: At intervals not exceeding 100 hours time in service, after 6 October 1968.\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\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused specifically on tail rotor yoke inspection for one helicopter series. It has not expanded beyond its original safety purpose. The document appears to be a complete, standalone directive as originally issued."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 2 defined part numbers (P/N 204-010-781-9 and 204-010-781-5)","Single, clear compliance requirement with no nested conditions or exceptions","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Straightforward temporal trigger (6 October 1968) and recurring interval (100 hours time in service)","Technical specifications are precise but limited to three numerical parameters (1400 amps DC, 1100 amps AC, 4200 ampere turns)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific Bell helicopters.\n\n**What it does:**\nIt requires owners and operators of certain Bell 204B helicopters to regularly inspect a critical part called the **tail rotor yoke** (the component that connects the tail rotor blades to the helicopter). The inspection must use a **magnetic particle method** — a technique that detects cracks or defects in metal by applying magnetic fields and iron particles.\n\n**Who it affects:**\n- Owners and operators of **Bell 204B helicopters** fitted with specific tail rotor yoke part numbers: **204-010-781-9** or **204-010-781-5**\n- Maintenance engineers who perform the inspections\n\n**The specific requirements:**\n- **What to inspect:** The yoke assembly, paying special attention to the **threaded portion of the yoke spindle** (this is where stress fractures are most likely to occur)\n- **How to inspect:** Using magnetic particle inspection with strict electrical settings:\n  - Maximum **1400 amps DC** or **1100 amps AC**\n  - Maximum **4200 ampere turns** (a measure of magnetic field strength)\n- **How often:** Every **100 hours of flight time** (\"time in service\")\n- **When it started:** From **6 October 1968** onwards\n\n**Why it matters:**\nTail rotor failures can cause catastrophic loss of control. This AD was issued because the specific yoke design was found to be susceptible to cracking in the threaded spindle area. The mandatory, recurring inspection ensures cracks are caught before they cause in-flight failure. Non-compliance means the aircraft cannot legally fly in Australian airspace."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The source text is a standalone airworthiness directive and does not indicate any change to its own scope from an earlier or original intent. Nothing in the instrument’s text asserts a scope change."},"complexity_factors":["Narrow applicability limited to specific airframe model (204B) and two part numbers","Single, well-specified inspection action (magnetic particle inspection) reduces procedural ambiguity","Technical detail in the Requirement (specific amperage limits and ampere-turn cap) requires specialised equipment and trained personnel","Recurring compliance interval (every ≤100 flight hours) adds operational scheduling considerations","Directive is prescriptive with little text on follow-up actions or alternative compliance routes, leaving implementation detail to operators or regulator"],"plain_english_summary":"This directive requires owners/operators of Bell 204B helicopters fitted with tail rotor yokes P/N 204‑010‑781‑5 or ‑9 to perform recurring magnetic‑particle inspections of the yoke spindle (with specified current limits) at intervals not exceeding 100 flight hours.  \n\nIt forces repeated NDT of a critical threaded spindle to catch cracks early, imposing recurring inspection costs, downtime and reliance on correct technique and equipment."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-204-7-tail-rotor-yoke-inspection","history":"/api/acts/ad-bell-204-7-tail-rotor-yoke-inspection/history","analysis":"/api/acts/ad-bell-204-7-tail-rotor-yoke-inspection/analysis","conflicts":"/api/acts/ad-bell-204-7-tail-rotor-yoke-inspection/conflicts","importantCases":"/api/acts/ad-bell-204-7-tail-rotor-yoke-inspection/important-cases","documents":"/api/acts/ad-bell-204-7-tail-rotor-yoke-inspection/documents"}}