{"id":"F2006B04630","name":"AD/BELL 407/17 - Forward Bearing Hanger Support","slug":"ad-bell-407-17-forward-bearing-hanger-support","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44382,"registerId":"commonwealth-F2006B04630-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\n![](image.001.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\nBell Helicopter Textron Canada (BHTC) 407 Series Helicopters","sortOrder":0},{"sectionNumber":"AD/BELL 407/17 Forward Bearing Hanger Su","sectionType":"part","heading":"AD/BELL 407/17 Forward Bearing Hanger Support 12/2001","content":"# AD/BELL 407/17 Forward Bearing Hanger Support 12/2001\n\nDM\n\nApplicability: Bell 407 series helicopters, serial numbers 53000 through 53442 with flywheel 407-\n\n040-316-101 installed.\n\nRequirement: Visually inspect the forward bearing hanger support in accordance with BHTC Alert Service Bulletin 407-01-39, Revision A. If a crack is detected, replace the affected support before further flight.\n\nNote 1: Transport Canada AD CF-2001-32 refers.\n\nNote 2: Compliance with a later revision of the referenced alert service bulletin satisfies the intent of this Airworthiness Directive.\n\nCompliance: Unless previously accomplished, within 25 flight hours after the effective date of this Airworthiness Directive and thereafter at intervals not to exceed 25 flight hours.\n\nThis Airworthiness Directive becomes effective on 24 October 2001.\n\nBackground: Bell has advised that cracks have been found in the forward bearing hanger support.\n\nWhile none of the incidents have resulted in loss of tail rotor drive/control, an inspection has been introduced to preclude such a condition until remedial action has been developed.\n\n![](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 15 October 2001\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 24 October 2001.","sortOrder":1}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, targeted airworthiness directive addressing a specific safety defect in a defined aircraft population. The scope remains precisely limited to the identified unsafe condition (cracked forward bearing hanger supports) and the specified helicopter series. No scope creep is evident."},"complexity_factors":["Single, clearly defined applicability (specific serial number range plus specific part number)","One straightforward requirement (visual inspection with reference to external service bulletin)","Simple binary compliance trigger (crack found = replace before flight)","Clear, fixed compliance interval (25 flight hours, recurring)","No nested exceptions, conditional logic, or alternative compliance methods","Only 2 brief notes, both informational rather than creating additional obligations","Total length: approximately 250 words"],"plain_english_summary":"CASA requires mandatory visual inspections of the forward bearing hanger support for cracks on Bell 407 helicopters (S/N 53000–53442) with flywheel P/N 407-040-316-101. Inspections start within 25 flight hours after 24 October 2001 and repeat every 25 flight hours; any cracked support must be replaced before the helicopter flies again.\n\nThis legally binding directive affects operators, pilots and maintenance crews and is intended to prevent loss of tail-rotor control after reported cracks."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD is narrowly focused on an identified unsafe condition (cracks in the forward bearing hanger support) and imposes an interim inspection-and-replace requirement for a specific subset of Bell 407 helicopters. It remains within that original, remedial scope rather than expanding to unrelated components, aircraft types, or regulatory objectives."},"complexity_factors":["Short, single-page instrument with limited provisions","One narrow applicability clause (Bell 407 serial numbers 53000–53442 with flywheel 407-040-316-101)","Single operational requirement: visual inspection per BHTC Alert Service Bulletin 407-01-39 Rev A","Simple binary remediation: replace if crack detected","Recurrent compliance interval specified (every 25 flight hours)","Two external cross-references (BHTC service bulletin and Transport Canada AD CF-2001-32)","No separate definitions section, no nested exceptions, and no complex conditional logic"],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- Requires owners/operators of certain Bell 407 helicopters to carry out a visual inspection of the forward bearing hanger support. (See: \"Requirement\".)\n- The inspection must follow Bell Helicopter Textron Canada (BHTC) Alert Service Bulletin 407-01-39, Revision A (the manufacturer’s inspection instructions). (See: \"Requirement\" and Note 2.)\n- If a crack is found during inspection, the affected hanger support must be replaced before the helicopter flies again. (See: \"Requirement\".)\n- Applies only to Bell 407 helicopters with serial numbers 53000 through 53442 that have flywheel part number 407-040-316-101 installed. (See: \"Applicability\".)\n- Inspections must be done within 25 flight hours after the AD becomes effective and then repeated at intervals not exceeding 25 flight hours. (See: \"Compliance\".)\n\n**Why this was issued (official rationale)**\n\n- The stated reason is that cracks were found in the forward bearing hanger support and the inspection requirement is an interim measure to reduce the risk of loss of tail-rotor drive/control until a permanent fix is developed. (See: \"Background\".)\n\n**Who is affected and who pays**\n\n- Affected: Owners/operators of the specific Bell 407 helicopters in the serial number range that have the specified flywheel installed. (Applicability.)\n- Who pays: the helicopter owner/operator pays for the inspections, any replacement parts and associated labour, and any aircraft downtime required to carry out the work. Maintenance organisations or contracted engineers will usually perform the inspections and replacements.\n\n**Who decides and how compliance is enforced**\n\n- The Civil Aviation Safety Authority (CASA), through its delegate, issued the AD under subregulation 39.1(1) of the Civil Aviation Regulations 1998, making the inspection and replacement mandatory for the identified aircraft. (Preamble and signature.)\n- The AD references the manufacturer’s service bulletin as the method of compliance; complying with a later revision of that bulletin also meets the AD. (Note 2.)\n\n**Practical effects and trade-offs**\n\n- Immediate safety action: introduces a short-interval, recurring visual inspection targeted at a known cracking issue to reduce immediate risk. (Requirement; Background.)\n- Operational cost and downtime: inspections every 25 flight hours are frequent and will impose recurring maintenance time and cost on operators; if cracking is found, there is additional replacement cost and further downtime. (Compliance; Requirement.)\n- Market effects: maintenance providers and parts suppliers may see increased demand (concentrated benefit). Costs fall directly on operators whose aircraft meet the applicability criteria (concentrated cost for those owners; diffuse safety benefit to the public/users).  \n- Incentives: the AD creates a short-term imperative to inspect and replace affected parts; it also encourages the manufacturer to develop a lasting engineering fix so the recurring inspection requirement can be removed or revised. (Background; Note 2.)\n- Implementation risk: the inspection mandated is a visual inspection — this may not detect very small or subsurface cracks, so the measure is an interim mitigant rather than a guaranteed prevention of failure. The AD explicitly treats it as an interim action until a remedial action is developed. (Background.)\n\n**Other procedural points**\n\n- The AD cross-references Transport Canada AD CF-2001-32 for the same issue. (Note 1.)\n- The AD became effective on 24 October 2001. (Compliance.)\n\nOverall, the AD imposes a narrowly targeted, mandatory inspection and replacement obligation on particular Bell 407 helicopters to manage a known cracking issue on the forward bearing hanger support. It is an interim, recurring safety requirement that shifts inspection and repair costs to affected operators while relying on the manufacturer’s service bulletin as the compliance method. (Applicability; Requirement; Compliance; Background.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-407-17-forward-bearing-hanger-support","history":"/api/acts/ad-bell-407-17-forward-bearing-hanger-support/history","analysis":"/api/acts/ad-bell-407-17-forward-bearing-hanger-support/analysis","conflicts":"/api/acts/ad-bell-407-17-forward-bearing-hanger-support/conflicts","importantCases":"/api/acts/ad-bell-407-17-forward-bearing-hanger-support/important-cases","documents":"/api/acts/ad-bell-407-17-forward-bearing-hanger-support/documents"}}