{"id":"F2006B04713","name":"AD/BELL 47/91 - Tail Rotor Blade Assembly P/N 47-642-117-1 - Replacement","slug":"ad-bell-47-91-tail-rotor-blade-assembly-p-n-47-642-117-1-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44477,"registerId":"commonwealth-F2006B04713-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 47/91 - Tail Rotor Blade Assembly P/N 47-642-117-1 - Replacement","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\n# AD/BELL 47/91  Tail Rotor Blade Assembly P/N 47-642-117-1 - Replacement\n\nApplicability: All models. Requirement Document Bell Helicopter Alert S.B. 47-84-11.\n\n# 1/85\n\n \n\nCompliance: Within 100 hours time in service after 31 January 1985 or at the next scheduled inspection for maintenance release issue. Whichever is the later.\n\n \n\nBackground: The manufacturer advises that bonding voids may have occurred in the root areas of tail rotor blade assemblies, S/Nos A-8 through A-72. A bonding void was found during periodic destructive testing.\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":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1064},"content_quality":"ok","complexity_score":1,"scope_assessment":{"changed":false,"description":"This is the original directive establishing the replacement requirement. The scope remains limited to the specific tail rotor blade assemblies identified in the manufacturer's service bulletin."},"complexity_factors":["Single-page document with no interpretation section","No defined terms or legal cross-references","Single compliance action with clear timeframe","Plain language background section explaining the safety risk"],"plain_english_summary":"**What this is:** A mandatory safety order (called an Airworthiness Directive) issued by the Civil Aviation Safety Authority requiring helicopter operators to replace faulty tail rotor blades.\n\n**Who it affects:** Owners and operators of all Bell 47 series helicopters.\n\n**What you must do:**\n- Replace tail rotor blade assemblies with part number **47-642-117-1** and serial numbers between **A-8 and A-72**\n- Do this within **100 hours of flight time** after 31 January 1985, or at your next scheduled maintenance inspection — whichever comes later\n\n**Why this matters:** The manufacturer discovered dangerous gaps (called \"bonding voids\") in the blade roots during testing. These defects could cause the tail rotor to fail, potentially leading to loss of control of the helicopter.\n\n**Reference:** You must follow the manufacturer's Alert Service Bulletin 47-84-11 when doing the replacement."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-47-91-tail-rotor-blade-assembly-p-n-47-642-117-1-replacement","history":"/api/acts/ad-bell-47-91-tail-rotor-blade-assembly-p-n-47-642-117-1-replacement/history","analysis":"/api/acts/ad-bell-47-91-tail-rotor-blade-assembly-p-n-47-642-117-1-replacement/analysis","conflicts":"/api/acts/ad-bell-47-91-tail-rotor-blade-assembly-p-n-47-642-117-1-replacement/conflicts","importantCases":"/api/acts/ad-bell-47-91-tail-rotor-blade-assembly-p-n-47-642-117-1-replacement/important-cases","documents":"/api/acts/ad-bell-47-91-tail-rotor-blade-assembly-p-n-47-642-117-1-replacement/documents"}}