{"id":"F2006B04352","name":"AD/BELL 204/8 - Main Rotor Blade - Modification","slug":"ad-bell-204-8-main-rotor-blade-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44166,"registerId":"commonwealth-F2006B04352-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 204/8 - Main Rotor Blade - 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 204 Series Helicopters\n\n \n\nAD/BELL 204/8 Main Rotor Blade - Modification NK\n\nApplicability: All model 204B.\n\nDocument: Bell SL No. 204B-68.\n\nCompliance: Within 100 hours time in service after 14 February 1969 for blades in service at that date. Before installation on an aircraft for all other blades.\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\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Based on the text provided, the directive sets a clear, narrow scope (all model 204B) and prescribes a single mandated modification procedure and two timing pathways. There is no indication in the supplied text that the scope has been expanded or altered from its apparent original purpose of mandating that modification; therefore no scope change is evident from this instrument as presented."},"complexity_factors":["Narrow applicability: applies to a single helicopter model (All model 204B) which limits scope but requires precise operator identification (Applicability).","External technical reference: the AD mandates compliance with Bell SL No. 204B-68 rather than reproducing technical steps, requiring operators to obtain and follow an external document (Document).","Two-tier compliance timing: different deadlines for blades already in service on a historical date versus blades not in service, which requires verification of blade service history (Compliance).","Historical trigger date (14 February 1969) and short working window (100 hours TIS) may complicate record-keeping and retrospective compliance for in-service blades (Compliance).","Absence of an explicit rationale or enforcement detail in the text increases practical uncertainty about the underlying risk and enforcement mechanisms (no explicit rationale in text)."],"plain_english_summary":"This AD, issued by the Civil Aviation Safety Authority under Part 39, mandates a specific modification to main rotor blades on Bell 204B helicopters, to be carried out exactly as described in Bell Service Letter No. 204B‑68. For blades in service on 14 Feb 1969 the work had to be done within 100 flight hours after that date; blades not in service then must be modified before installation. Owners/operators bear the costs and must change maintenance/procurement practices to ensure mandatory compliance."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive from 1969 concerning one specific helicopter model component. It has not expanded beyond its original narrow safety purpose."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 1 defined applicability criterion (model 204B)","Single compliance pathway with two simple temporal conditions (in-service vs new blades)","No cross-references to other legislation beyond the enabling regulations (Civil Aviation Regulations 1998, Part 39)","No nested exceptions or conditional logic","References only one external technical document (Bell SL No. 204B-68) without incorporating its contents"],"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) under the Civil Aviation Regulations 1998.\n\n**What it does:** It requires a specific modification to the **main rotor blades** on certain Bell helicopters (the 204B model series).\n\n**Who it affects:** Anyone who owns, operates, or maintains Bell 204B helicopters.\n\n**The requirement:**\n- **For blades already in use** on aircraft as of 14 February 1969: The modification must be done within **100 hours of flying time** after that date.\n- **For blades not yet installed** on an aircraft: The modification must be completed **before the blade is fitted to any helicopter**.\n\n**Why it matters:** Main rotor blades are critical to helicopter safety. This directive ensures all 204B blades meet an updated safety standard (detailed in Bell Service Letter No. 204B-68) to prevent potential failures that could lead to accidents.\n\n**Key point:** This is not optional. Compliance is legally mandatory for airworthiness (meaning the aircraft is legally allowed to fly)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-204-8-main-rotor-blade-modification","history":"/api/acts/ad-bell-204-8-main-rotor-blade-modification/history","analysis":"/api/acts/ad-bell-204-8-main-rotor-blade-modification/analysis","conflicts":"/api/acts/ad-bell-204-8-main-rotor-blade-modification/conflicts","importantCases":"/api/acts/ad-bell-204-8-main-rotor-blade-modification/important-cases","documents":"/api/acts/ad-bell-204-8-main-rotor-blade-modification/documents"}}