{"id":"F2006B04392","name":"AD/BELL 205/56 - Tail Rotor Hub P/N 204-011-801-121","slug":"ad-bell-205-56-tail-rotor-hub-p-n-204-011-801-121","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44217,"registerId":"commonwealth-F2006B04392-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 205/56 - Tail Rotor Hub P/N 204-011-801-121","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 205 Series Helicopters\n\n \n\nAD/BELL 205/56 Tail Rotor Hub P/N 204-011-801-121 13/89\n\nTX\n\n \n\nApplicability: Model 205A and 205A-1.\n\n \n\nRequirement: Inspect the tail rotor hub assembly and remove from service any of the subject part number hub assemblies identified with any serial number IT0001 to IT0010 inclusive.\n\n \n\nNote: FAA AD 89-20-12 refers.\n\n \n\nCompliance: Prior to further flight after 23 October 1989.\n\n \n\nBackground: The listed serial number hub assemblies may have been incorrectly assembled, do not have the required component preloads, are not dynamically balanced, or do not conform to the approved type design.\n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive targeting a specific manufacturing defect in a specific part. It has not expanded beyond its original purpose of grounding defective tail rotor hubs."},"complexity_factors":["Single, specific mechanical component targeted (tail rotor hub)","Narrow applicability: only 2 helicopter models (205A and 205A-1)","Clear serial number range (IT0001-IT0010) leaves no ambiguity","Single compliance action: inspect and remove if matched","No conditional logic, exceptions, or alternative compliance methods","Short document with minimal cross-referencing (only one FAA reference note)","No defined terms section — plain language throughout"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nOrders owners and operators of certain Bell 205 series helicopters to immediately inspect their tail rotor hubs. If the hub has part number 204-011-801-121 AND a serial number between IT0001 and IT0010, it must be removed from service before the helicopter flies again.\n\n**Who it affects:**\n- Owners and operators of **Bell 205A and 205A-1 helicopters**\n- Anyone maintaining these aircraft\n\n**Why it matters:**\nThe affected tail rotor hubs may have been assembled incorrectly — they might lack proper tension on components (preload), might not be balanced properly, or might not meet the approved design standards. A faulty tail rotor hub could fail in flight, causing loss of control and potentially a crash. This is an urgent safety fix with a hard deadline of **23 October 1989**.\n\n**Key details:**\n- **Compliance deadline:** Before flying again after 23 October 1989\n- **Reference:** Matches US FAA directive 89-20-12 (showing international coordination on this safety issue)\n- **Action required:** Visual inspection and removal of affected parts — no repair option offered, just removal"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD's scope, as described in the text, is limited to Model 205A and 205A-1 helicopters and to tail rotor hub assemblies P/N 204-011-801-121 with serial numbers IT0001–IT0010. The instrument requires inspection and removal from service of those listed parts prior to any further flight after 23 October 1989. The text does not indicate any change from that stated applicability or requirement; therefore the scope has not changed from the stated intent in the instrument. (Applicability; Requirement; Compliance)"},"complexity_factors":["Narrow applicability limited to Model 205A and 205A-1 and to ten specific serial-numbered hub assemblies reduces administrative complexity. (Applicability; Requirement)","Mandated binary actions (inspect; remove if serial-number matches) are procedurally simple but require qualified maintenance personnel to assess technical faults (preloads, dynamic balance, conformity). (Requirement; Background)","Fixed compliance condition tied to a flight prohibition after a specific date creates operational urgency and potential scheduling/resource complexity for operators. (Compliance)","No alternative compliance path or discretionary relief is provided in the text, which simplifies legal interpretation but increases operational pressure on owners/operators to comply exactly. (Requirement; Compliance)","Reference to external FAA AD adds coordination complexity for operators that must reconcile multiple regulatory documents. (Note)"],"plain_english_summary":"# What this directive does\n\n- Mechanically, this airworthiness directive (AD) requires operators of Bell Model 205A and 205A-1 helicopters to inspect the tail rotor hub assembly P/N 204-011-801-121 and remove from service any hub assembly bearing serial numbers IT0001 through IT0010 inclusive. (Requirement)\n- The AD prohibits further flight of affected helicopters unless this inspection and removal (where applicable) have been completed on or after 23 October 1989. (Compliance)\n\n# Who it affects\n\n- Owners and operators of Bell 205A and 205A-1 helicopters that have tail rotor hub part number 204-011-801-121. (Applicability; Requirement)\n\n# Why the rule exists (stated purpose)\n\n- The AD states that the listed serial-numbered hub assemblies may have been incorrectly assembled, may lack required component preloads, may not be dynamically balanced, or may not conform to approved type design. The AD references FAA AD 89-20-12. (Background; Note)\n\n# Practical effects, who pays and who decides\n\n- Who pays: Aircraft owners/operators bear the direct costs of inspecting hubs and of removing and replacing any identified hub assemblies. (Requirement)\n- Who decides: The Civil Aviation Safety Authority issued the AD and set the mandatory requirement and compliance deadline; the text contains no provision for regulatory waiver or discretionary exemption. (Requirement; Compliance)\n- Behaviour change required: Operators must inspect specified hub assemblies and remove from service any with serial numbers IT0001–IT0010 before the affected helicopter is flown after 23 October 1989. (Requirement; Compliance)\n\n# Implementation mechanics and trade-offs (analysis)\n\n- Inspection and removal are concrete, binary actions: inspect the hub assembly; if its serial number is in the listed range, remove it from service. (Requirement)\n- Compliance timing is immediate relative to the stated date: the AD forbids further flight after the compliance date until the requirement is met, which creates operational downtime for affected helicopters. (Compliance)\n- Costs and opportunity costs: the requirement imposes inspection costs and, for removed hubs, replacement costs and aircraft downtime. The text does not specify supply or reimbursement mechanisms. (Requirement)\n- Technical competence and verification: the Background identifies technical faults (incorrect assembly, missing preloads, lack of dynamic balance, non-conformity to type design) that require qualified maintenance personnel to detect and to rectify by replacing the hub. This creates a technical compliance burden on operators and maintenance organisations. (Background; Requirement)\n- Enforcement and discretion: the AD is prescriptive and sets a non‑negotiable compliance condition tied to flight status; the text does not provide discretionary exceptions or alternative means of compliance. (Requirement; Compliance)\n\n# Risks, incentives and potential substitution effects\n\n- The primary operational incentive for owners/operators is to inspect and, where necessary, remove the listed hub assemblies to restore lawful flight operations. (Requirement; Compliance)\n- Because the AD targets only ten serial-numbered hub assemblies, benefits (risk reduction) are concentrated on aircraft with those specific parts while costs (inspection and possible replacement) fall on the owners/operators of affected helicopters. (Applicability; Requirement)\n- The AD references a parallel FAA action, indicating alignment with an external regulator’s identification of the same risk, but the text provides no detail on alternative mitigations or longer-term corrective measures. (Note)\n\n# Source citations\n\n- Applicability: \"Model 205A and 205A-1.\" (Applicability)\n- Required action: \"Inspect the tail rotor hub assembly and remove from service any of the subject part number hub assemblies identified with any serial number IT0001 to IT0010 inclusive.\" (Requirement)\n- Compliance deadline: \"Prior to further flight after 23 October 1989.\" (Compliance)\n- Stated reason: \"The listed serial number hub assemblies may have been incorrectly assembled, do not have the required component preloads, are not dynamically balanced, or do not conform to the approved type design.\" (Background)\n- Cross-reference: \"FAA AD 89-20-12 refers.\" (Note)\n"}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-205-56-tail-rotor-hub-p-n-204-011-801-121","history":"/api/acts/ad-bell-205-56-tail-rotor-hub-p-n-204-011-801-121/history","analysis":"/api/acts/ad-bell-205-56-tail-rotor-hub-p-n-204-011-801-121/analysis","conflicts":"/api/acts/ad-bell-205-56-tail-rotor-hub-p-n-204-011-801-121/conflicts","importantCases":"/api/acts/ad-bell-205-56-tail-rotor-hub-p-n-204-011-801-121/important-cases","documents":"/api/acts/ad-bell-205-56-tail-rotor-hub-p-n-204-011-801-121/documents"}}