{"id":"F2006B04711","name":"AD/BELL 47/89 - Flight Control Systems - Hydraulic Servo to Swashplate Control Plate Attachment Bolts","slug":"ad-bell-47-89-flight-control-systems-hydraulic-servo-to-swashplate-control-plate-attachment-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44475,"registerId":"commonwealth-F2006B04711-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 47/89 - Flight Control Systems - Hydraulic Servo to Swashplate Control Plate Attachment Bolts","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 47/89 Flight Control Systems - Hydraulic Servo to\n\nSwashplate Control Plate Attachment Bolts\n\nApplicability: All 47G, J and K series aircraft. Document:  Bell Alert Service Bulletin 47-83-8. Compliance:               By 31 December 1983.\n\n# 10/83\n\nBackground: There have been two reported failures on AN Standard bolts, installed in the above flight control application where BHTI standard bolts should have been used.\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":2,"scope_assessment":{"changed":false,"description":"The directive’s scope — requiring the actions in Bell Alert Service Bulletin 47-83-8 for all Bell 47G, J and K series aircraft by a set date — aligns with the stated purpose of addressing failures caused by incorrect bolt installation (see: \"Applicability...\", \"Document...\", \"Compliance...\", and \"Background...\"). There is no indication in the instrument text that the scope departs from the original intent to correct the specific hardware fault."},"complexity_factors":["Narrow applicability limited to three specific aircraft variants (47G, J and K).","Clear compliance deadline explicitly stated (By 31 December 1983).","Technical corrective action is delegated to a single named manufacturer service bulletin (Bell Alert Service Bulletin 47-83-8), creating a single external dependency.","Technical issue is specific (incorrect bolt type: AN Standard bolts used where BHTI standard bolts were required), reducing interpretive ambiguity.","Regulatory context is straightforward: Schedule of Airworthiness Directives (Part 39 - 105) enforces compliance."],"plain_english_summary":"What this instrument does (mechanically)\n\n- Requires operators/owners of certain Bell 47 helicopters to follow a specified manufacturer's alert service bulletin by a set date. The directive names the relevant service document as Bell Alert Service Bulletin 47-83-8 and sets a compliance deadline of 31 December 1983 (see: \"Document: Bell Alert Service Bulletin 47-83-8\"; \"Compliance: By 31 December 1983\").\n\nWho is affected\n\n- Aircraft owners and operators of Bell Helicopter Textron 47 series: all 47G, J and K series aircraft (see: \"Applicability: All 47G, J and K series aircraft\").\n- Maintenance organisations and engineers who carry out inspections and corrective work on those helicopters.\n- The Civil Aviation Safety Authority insofar as it enforces the directive under the Schedule of Airworthiness Directives (Part 39 - 105).\n\nWhy it matters (official rationale and how the mechanics address it)\n\n- The background states there were two reported failures of AN Standard bolts when AN bolts were installed in a flight control attachment where BHTI standard bolts should have been used (see: \"Background: There have been two reported failures on AN Standard bolts, installed in the above flight control application where BHTI standard bolts should have been used\").\n- Mechanically, the directive compels those responsible for the listed helicopters to take the action set out in the named service bulletin by the stated date. The service bulletin will specify the technical corrective measures (inspection, replacement or reinstallation of the correct BHTI standard bolts) required to remove the safety risk identified.\n\nWho pays and who decides\n\n- The immediate financial cost and operational disruption fall on aircraft owners/operators who must arrange and pay for the work required by the service bulletin (parts and labour). This follows from the directive’s requirement that operators comply with the named bulletin by the deadline (see: \"Document... Compliance...\").\n- Regulatory enforcement and monitoring are functions of the administering authority under the Schedule of Airworthiness Directives (Part 39 - 105).\n\nCompliance burden, discretion and implementation points\n\n- Compliance is time-bound: work must be completed by the stated compliance date (\"By 31 December 1983\").\n- The AD delegates the technical content of the corrective action to the manufacturer’s service bulletin (\"Document: Bell Alert Service Bulletin 47-83-8\"). That means the precise steps, parts and maintenance standard are defined in that bulletin rather than in the short AD text itself.\n- The AD targets specific aircraft variants only (47G, J and K), so owners/operators of other variants are not covered by this instrument (\"Applicability: All 47G, J and K series aircraft\").\n\nPractical trade-offs, incentives and risks (source-grounded)\n\n- Incentive structure: operators are required to act (inspect/replace) to mitigate a documented hardware failure mode; failure to comply risks regulatory enforcement under the Schedule of Airworthiness Directives (Part 39 - 105).\n- Costs for owners are concentrated (parts and labour for the covered fleet). Any safety benefit (reduced risk of bolt failure) accrues to operators, their passengers, and third parties; the AD does not allocate financial compensation or subsidies.\n- The AD relies on the manufacturer’s bulletin for technical detail. That creates dependence on the manufacturer’s specified parts/standards (BHTI standard bolts versus AN Standard bolts) to resolve the identified failure mode.\n\nSource references: applicability, document and compliance deadline are stated in the instrument; the background reports two bolt failures when the incorrect bolt type was installed."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in specific aircraft models. It has not expanded beyond its original purpose of mandating bolt replacement to prevent flight control failures."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined terms implicitly referenced (AN Standard bolts, BHTI standard bolts — explained in plain English in the background)","Single compliance action with clear deadline","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","No conditional logic or exceptions — applies to all listed aircraft variants without exemption clauses","Straightforward applicability statement (all 47G, J and K series)"],"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:**\nOrders owners and operators of specific Bell 47 helicopters to replace certain bolts in the flight control system. The bolts connect the hydraulic servo (a power-assist component that helps move the rotor blades) to the swashplate control plate (a key part that translates pilot inputs into rotor blade movement).\n\n**The problem:**\nTwo bolts failed because the wrong type was installed — someone used \"AN Standard\" bolts instead of the stronger \"BHTI standard\" bolts specified by the manufacturer (Bell Helicopter Textron). Failed bolts in flight controls can cause loss of control and crash.\n\n**Who it affects:**\nOwners and operators of all Bell 47G, 47J, and 47K series helicopters.\n\n**What they must do:**\nReplace the incorrect bolts with the correct ones by **31 December 1983**, following the manufacturer's instructions in Bell Alert Service Bulletin 47-83-8.\n\n**Why it matters:**\nThis is a critical safety fix. Flight control failures are catastrophic. The directive makes compliance mandatory — not optional — to prevent accidents."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-47-89-flight-control-systems-hydraulic-servo-to-swashplate-control-plate-attachment-bolts","history":"/api/acts/ad-bell-47-89-flight-control-systems-hydraulic-servo-to-swashplate-control-plate-attachment-bolts/history","analysis":"/api/acts/ad-bell-47-89-flight-control-systems-hydraulic-servo-to-swashplate-control-plate-attachment-bolts/analysis","conflicts":"/api/acts/ad-bell-47-89-flight-control-systems-hydraulic-servo-to-swashplate-control-plate-attachment-bolts/conflicts","importantCases":"/api/acts/ad-bell-47-89-flight-control-systems-hydraulic-servo-to-swashplate-control-plate-attachment-bolts/important-cases","documents":"/api/acts/ad-bell-47-89-flight-control-systems-hydraulic-servo-to-swashplate-control-plate-attachment-bolts/documents"}}