{"id":"F2006B04527","name":"AD/BELL 206/74 - Tail Rotor Drive Shaft Bearings - Replacement","slug":"ad-bell-206-74-tail-rotor-drive-shaft-bearings-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114238,"registerId":"commonwealth-F2006B04527-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 206/74 - Tail Rotor Drive Shaft Bearings - 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\nBell Helicopter Textron Canada (BHTC) 206 and Agusta Bell 206 Series Helicopters\n\n \n\nAD/BELL 206/74 Tail Rotor Drive Shaft Bearings - Replacement 4/74\n\nApplicability: All models AB206, 206A and 206B as referenced in requirement documents. Document:               Bell SB 206-76-12, Rev. A, or Agusta SB No. BT206-116, Rev. A. Compliance:               Within 100 hours time in service after 30 April 1977.\n\nBackground: AD/Agusta 206/59 equivalent.\n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-purpose airworthiness directive focused specifically on tail rotor drive shaft bearing replacement. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 4 defined elements: Applicability, Document, Compliance, and Background","No nested conditional logic or cross-references to other legislation","Single straightforward requirement with clear deadline","References only two manufacturer service bulletins for technical details"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific Bell and Agusta-Bell helicopter models to replace certain bearings in the tail rotor drive shaft.\n\n**What it does:**\n- Mandates the replacement of tail rotor drive shaft bearings on affected helicopters\n- References specific service bulletins from the manufacturers (Bell and Agusta) that detail the required work\n\n**Who it affects:**\n- Owners and operators of:\n  - Bell Helicopter Textron Canada (BHTC) 206 series helicopters\n  - Agusta Bell 206 series helicopters\n  - Specifically models: AB206, 206A, and 206B\n\n**Why it matters:**\n- Tail rotor drive shaft bearings are critical components — if they fail, the pilot can lose control of the helicopter's yaw (directional control), potentially causing a crash\n- This directive was issued to address a known safety defect before it causes accidents\n- Compliance is mandatory within 100 hours of flight time after 30 April 1977\n\n**Key deadline:** The work must be done within 100 hours of flying time after 30 April 1977 (this is a historical directive from 1974, updated in context of 1977 compliance)."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive as presented does not indicate any change to the scope of affected aircraft or the required action. It applies to all AB206, 206A and 206B models as stated (Applicability), requires bearing replacement per the cited service bulletins (Document), and sets a specific compliance window (Compliance). The background notes equivalence to a prior AD (Background), but the text does not show any expansion or narrowing of scope from that reference."},"complexity_factors":["Narrow and specific applicability to AB206, 206A and 206B models (Applicability).","Compliance requires following external manufacturer service bulletins rather than containing full technical detail (Document).","A fixed, date-linked compliance window (100 hours after 30 April 1977) which creates a clear but time-sensitive scheduling requirement (Compliance).","No alternative compliance methods or enforcement details are provided in the text, leaving procedural questions to regulator or maintenance organisations (Document, Compliance).","Background references an equivalent prior AD but does not expand on the technical rationale or risk assessment (Background)."],"plain_english_summary":"This directive mandates replacement of the tail-rotor drive‑shaft bearings on affected Bell/Agusta Bell 206 helicopters (AB206, 206A, 206B). Owners, operators and maintenance organisations must complete the work within 100 hours TIS after 30 April 1977 by following the referenced Bell/Agusta service bulletins. It is a mandatory safety action that preserves airworthiness; parts, labour and downtime costs are the operators’ responsibility."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-206-74-tail-rotor-drive-shaft-bearings-replacement","history":"/api/acts/ad-bell-206-74-tail-rotor-drive-shaft-bearings-replacement/history","analysis":"/api/acts/ad-bell-206-74-tail-rotor-drive-shaft-bearings-replacement/analysis","conflicts":"/api/acts/ad-bell-206-74-tail-rotor-drive-shaft-bearings-replacement/conflicts","importantCases":"/api/acts/ad-bell-206-74-tail-rotor-drive-shaft-bearings-replacement/important-cases","documents":"/api/acts/ad-bell-206-74-tail-rotor-drive-shaft-bearings-replacement/documents"}}