{"id":"F2006B04701","name":"AD/BELL 47/78 - Main Rotor Gimbal Rings - Retirement Life","slug":"ad-bell-47-78-main-rotor-gimbal-rings-retirement-life","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44465,"registerId":"commonwealth-F2006B04701-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 47/78 - Main Rotor Gimbal Rings - Retirement Life","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 47 (All Variants) Series Helicopters\n\n \n\nAD/BELL 47/78 Main Rotor Gimbal Rings - Retirement Life 5/76\n\nApplicability: All models. Document:  Bell SB 47-76-4. Effective:  1 September 1976.\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":4,"scope_assessment":{"changed":false,"description":"The supplied AD entry does not show any amendment history or language indicating the scope has been widened or narrowed from an earlier instrument. It states the subject (retirement life for main rotor gimbal rings), its applicability (all models), the controlling service bulletin (Bell SB 47-76-4) and an effective date (1 September 1976). No information in the provided text indicates a change in scope from an original intent."},"complexity_factors":["Reference to an external technical document (Bell SB 47-76-4) for the operative technical requirements rather than including numeric limits or procedures in the AD text","Absence in the supplied text of the numeric retirement life, inspection or replacement procedures","Broad applicability (applies to all Bell 47 models) increases the range of affected operators and maintenance contexts","Regulatory placement in a schedule (Civil Aviation Regulations 1998, Part 39) implies administrative and enforcement context not detailed in the entry","Potential for uncertainty about permissible alternatives, enforcement steps or transitional arrangements because those details are not included in the supplied excerpt"],"plain_english_summary":"This Airworthiness Directive sets a mandatory retirement life for the main rotor gimbal rings on all Bell 47 series helicopters, effective 1 September 1976, and implements the technical limits by reference to Bell Service Bulletin SB 47-76-4. It affects Bell 47 owners, operators and maintenance organisations by forcing component removal/replacement per the bulletin, changing maintenance scheduling and costs; technical details and intervals must be obtained from the referenced service bulletin."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused specifically on retirement life limits for one component on one aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Extremely short document — essentially a single paragraph directive","Only one defined reference (Bell SB 47-76-4)","No conditional logic, exceptions, or nested provisions","Simple applicability statement ('All models')","No cross-references to other legislation beyond the enabling Civil Aviation Regulations 1998","Straightforward command: retire component at specified life limit"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\n- Requires owners and operators of **Bell 47 series helicopters** (all models) to retire (permanently remove from service) the **main rotor gimbal rings** after they reach a specified service life limit.\n- A \"gimbal ring\" is a critical component that helps the main rotor tilt and move, allowing the helicopter to fly and manoeuvre. If it fails, the rotor can detach — catastrophic.\n\n**Who it affects:**\n- Anyone who owns, operates, or maintains Bell 47 helicopters in Australia.\n\n**Why it matters:**\n- Metal parts on helicopters wear out from stress and vibration. This rule prevents crashes by forcing replacement of these rings before they can fail from metal fatigue.\n- It references **Bell Service Bulletin 47-76-4** — the manufacturer's official technical notice specifying the retirement life.\n- It became mandatory in Australia on **1 September 1976**.\n\n**In short:** If you fly or fix Bell 47 helicopters, you must count the flight hours or cycles on these gimbal rings and scrap them when they hit the limit set by the manufacturer."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-47-78-main-rotor-gimbal-rings-retirement-life","history":"/api/acts/ad-bell-47-78-main-rotor-gimbal-rings-retirement-life/history","analysis":"/api/acts/ad-bell-47-78-main-rotor-gimbal-rings-retirement-life/analysis","conflicts":"/api/acts/ad-bell-47-78-main-rotor-gimbal-rings-retirement-life/conflicts","importantCases":"/api/acts/ad-bell-47-78-main-rotor-gimbal-rings-retirement-life/important-cases","documents":"/api/acts/ad-bell-47-78-main-rotor-gimbal-rings-retirement-life/documents"}}