{"id":"F2006B04638","name":"AD/BELL 407/25 Amdt 1 - Tail Rotor Drive Shaft Bearings","slug":"ad-bell-407-25-amdt-1-tail-rotor-drive-shaft-bearings","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44390,"registerId":"commonwealth-F2006B04638-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"2. Oil Cooler Blower Shaft Bearings:","sectionType":"part","heading":"2. Oil Cooler Blower Shaft Bearings:","content":"# 2. Oil Cooler Blower Shaft Bearings:\n\nFor helicopters S/N 53000 through 53579:\n\n    Replace oil cooler blower shaft bearings in accordance with BHTC ASB 407-04-63 Revision A.\n\n    b. Inspect oil cooler blower shaft bearings in accordance with BHT ASB 407- 04-63 Revision A.\n\n    c. Lubricate oil cooler blower shaft bearings in accordance with BHTC ASB 407-04-63 Revision A.\n\n    d. Replace lubrication-warning decal in accordance with BHTC ASB 407-04- 63 Revision A.","sortOrder":0},{"sectionNumber":"3. Tail Rotor Segmented Drive Shaft Bear","sectionType":"part","heading":"3. Tail Rotor Segmented Drive Shaft Bearings:","content":"# 3. Tail Rotor Segmented Drive Shaft Bearings:\n\n    Replace oil cooler blower shaft bearings in accordance with BHTC ASB 407-04-63 Revision A.\n\n    b. Inspect tail rotor drive shaft bearings in accordance with BHTC ASB 407- 04-63 Revision A.","sortOrder":1},{"sectionNumber":"Requirement 2. Oil Cooler Blower Shaft B","sectionType":"part","heading":"Requirement 2. Oil Cooler Blower Shaft Bearings:","content":"# Requirement 2. Oil Cooler Blower Shaft Bearings:\n\n    Unless previously accomplished, within 300 flight hours from the effective date of this Directive or no later than 30 September 2004, whichever comes first.\n\n    b. Effective 30 September 2004; as detailed in Table 1 of BHTC ASB 407-04- 63 Revision A.\n\n    c. Effective 30 September 2004; as detailed in Table 2 of BHTC ASB 407-04- 63 Revision A.\n\n    d. Effective 30 September 2004; as detailed in Table 2 of BHTC ASB 407-04- 63 Revision A.","sortOrder":2},{"sectionNumber":"Requirement 3: Tail Rotor Segmented Driv","sectionType":"part","heading":"Requirement 3: Tail Rotor Segmented Drive Shaft Bearings:","content":"# Requirement 3: Tail Rotor Segmented Drive Shaft Bearings:\n\n    Unless previously accomplished, within 200 flight hours from the effective date of this Directive or no later than 30 September 2004, whichever comes first and as detailed in Table 1 of BHTC ASB 407-04-63 Revision A.\n\n    b. Effective 30 September 2004; as detailed in Table 2 of BHTC ASB 407-04- 63 Revision A.\n\n    c. Effective 30 September 2004; as detailed in Table 2 of BHTC ASB 407-04- 63 Revision A.\n\n    d. Effective 30 September 2004; as detailed in Table 2 of BHTC ASB 407-04- 63 Revision A.\n\nThis Amendment becomes effective on 15 September 2004.","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"This amendment imposes targeted mandatory maintenance tasks and compliance deadlines for a defined sub‑set of Bell 407 helicopters and ties the procedures to the manufacturer’s service bulletin. It does not broaden the affected fleet beyond the stated serial number range or extend the Directive to unrelated systems. The amendment primarily specifies timing and requires adherence to the ASB for procedures and ongoing intervals rather than expanding scope materially beyond the original safety focus on the listed bearings. The main practical change is the imposition of concrete compliance windows and linkage to ASB Tables 1 and 2; no evidence in the text suggests a significant expansion of the Directive's original technical scope."},"complexity_factors":["Narrow applicability: single helicopter type, serial numbers 53000–53579 (low scope breadth)","Cross-reference dependency: all procedures and recurring intervals delegated to BHTC ASB 407-04-63 Revision A (external document reliance increases implementation complexity)","Multiple distinct mandatory actions: replace, inspect, lubricate, replace decal (four action types) for oil cooler blower shaft bearings; replace and inspect for tail rotor drive shaft bearings","Two different compliance thresholds: Requirement 2 uses 300 flight hours or a calendar cut‑off; Requirement 3 uses 200 flight hours or the same calendar cut‑off (conditional timing adds complexity)","Calendar deadline plus flight‑hour whichever-comes-first rule (compound deadline condition)","Recurring interval specification deferred to Table 1 and Table 2 of the ASB (hidden complexity depending on those tables)","Small drafting issues and duplicated lines in the provided text create ambiguity/risk (implementation uncertainty)"],"plain_english_summary":"**What this instrument does**\n\n- It requires specific maintenance actions on certain Bell 407 helicopters (serial numbers 53000 through 53579).  The required work is to be done in accordance with the manufacturer service document BHTC ASB 407-04-63 Revision A.\n\n- The actions specified are:\n  - For the oil cooler blower shaft bearings: replace the bearings, inspect them, lubricate them, and replace the lubrication‑warning decal (each action \"in accordance with BHTC ASB 407-04-63 Revision A\"). (See Requirement 2.)\n  - For the tail rotor segmented drive shaft bearings: replace and inspect the tail rotor drive shaft bearings (also \"in accordance with BHTC ASB 407-04-63 Revision A\"). (See Requirement 3.)\n\n- Compliance timing:\n  - Oil cooler blower shaft bearings: unless already done, the work must be completed within 300 flight hours from the Directive's effective date or no later than 30 September 2004, whichever is earlier. From 30 September 2004, further actions and intervals are those listed in Tables 1 and 2 of the referenced ASB. (Requirement 2.)\n  - Tail rotor segmented drive shaft bearings: unless already done, the work must be completed within 200 flight hours from the Directive's effective date or no later than 30 September 2004, whichever is earlier; ongoing intervals are as set out in Table 1 and Table 2 of the ASB effective 30 September 2004. (Requirement 3.)\n\n- The amendment itself becomes effective on 15 September 2004.\n\n**Who this affects**\n\n- Aircraft operators and owners of Bell 407 helicopters with serial numbers 53000–53579.\n- Maintenance organisations and mechanics who perform inspections, replacements, lubrication and decal work.\n- Suppliers of the specified bearings and related parts.\n\n**Why it matters (mechanics, not motive)**\n\n- The Directive changes what maintenance must be done and by when. It imposes mandatory replacement, inspection, lubrication and labelling work for the listed components, referenced to the manufacturer’s service bulletin for the technical steps and for recurring intervals.\n\n- Practically, affected operators will need to schedule aircraft downtime, obtain parts, and document compliance to meet the stated flight‑hour or date deadlines. The regulator (the issuing authority) enforces compliance with the Directive; the ASB provides the technical procedures.\n\n**Costs, incentives, trade‑offs and implementation notes**\n\n- Who pays: operators/owners pay for parts, labour, and aircraft time out of service. Maintenance organisations may charge for labour and parts procurement. If parts are scarce, costs can rise and lead times lengthen.\n\n- Behaviour changes: operators must schedule and perform the mandated inspections/replacements earlier than they otherwise might, and follow the ASB’s procedures and recurring intervals after the calendar effective date.\n\n- Compliance burden: the Directive cross‑references the BHTC ASB 407-04-63 Revision A for the detailed procedures and for Tables 1 and 2 that set ongoing intervals; compliance therefore requires access to and reliance on that external document. That creates an administrative dependency and a potential cost for obtaining the ASB and any parts specified.\n\n- Opportunity cost: time and money spent complying may displace other maintenance or operational uses of the aircraft.\n\n- Effects on competition and independent providers: independent maintenance organisations can perform the work if permitted by their approvals, so the Directive does not in itself reserve work to a particular provider; however, if the ASB requires special parts or tooling, that may advantage suppliers who hold those parts or tooling.\n\n**Implementation risks and ambiguities**\n\n- The Directive relies heavily on the BHTC ASB (Revision A) and its Tables 1 and 2 for the detailed procedures and ongoing intervals; any ambiguity or unavailability of those tables creates implementation risk.\n\n- The text provided includes minor textual duplications and one apparent inconsistency (a line under the tail rotor section repeats the oil cooler action). That kind of drafting glitch could create momentary uncertainty about the precise mandated action, which in practice would be resolved by following the ASB and consulting the regulator for clarification.\n\n**Concrete references in the instrument**\n\n- Applicability: helicopters S/N 53000 through 53579.\n- Mandatory action references: BHTC ASB 407-04-63 Revision A.\n- Compliance windows: Requirement 2 — within 300 flight hours or by 30 September 2004; Requirement 3 — within 200 flight hours or by 30 September 2004.\n- Amendment effective date: 15 September 2004."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This appears to be a focused amendment to an existing Airworthiness Directive, specifically addressing bearing maintenance requirements for a defined serial number range. The scope remains tightly constrained to the original safety purpose — preventing bearing failures in critical helicopter systems. No evidence of scope creep beyond the original technical safety intent."},"complexity_factors":["Multiple overlapping deadlines (flight hours vs calendar dates with 'whichever comes first' logic)","Cross-references to external technical documents (BHTC ASB 407-04-63 Revision A, Tables 1 and 2) that are not reproduced in the directive","Serial number range limitation (S/N 53000 through 53579) creating conditional applicability","Nested effective dates with different triggers (immediate vs 30 September 2004)","Inconsistent formatting and apparent copy-paste errors in the source text (duplicate headings, truncated section titles) creating ambiguity about which requirements apply to which components","Split requirements across multiple tables in an external document requiring cross-referencing"],"plain_english_summary":"This mandatory CASA airworthiness directive requires owners/operators of Bell 407 helicopters (S/N 53000–53579) to replace, inspect and lubricate oil cooler blower shaft bearings, replace tail rotor segmented drive shaft bearings, and replace a lubrication-warning decal by specified flight-hour limits or by 30 Sep 2004. It targets operators and maintenance organisations because these bearings are safety-critical: failures can cause loss of engine cooling or tail-rotor control."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-407-25-amdt-1-tail-rotor-drive-shaft-bearings","history":"/api/acts/ad-bell-407-25-amdt-1-tail-rotor-drive-shaft-bearings/history","analysis":"/api/acts/ad-bell-407-25-amdt-1-tail-rotor-drive-shaft-bearings/analysis","conflicts":"/api/acts/ad-bell-407-25-amdt-1-tail-rotor-drive-shaft-bearings/conflicts","importantCases":"/api/acts/ad-bell-407-25-amdt-1-tail-rotor-drive-shaft-bearings/important-cases","documents":"/api/acts/ad-bell-407-25-amdt-1-tail-rotor-drive-shaft-bearings/documents"}}