{"id":"F2007L03911","name":"AD/BELL 407/31 - Disc Assemblies - Tail Rotor Driveshaft","slug":"ad-bell-407-31-disc-assemblies-tail-rotor-driveshaft","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":70557,"registerId":"commonwealth-F2007L03911-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Bell Helicopter Textron Canada (BHTC) 40","sectionType":"division","heading":"Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters","content":"### Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters\n\n| AD/BELL 407/31 | Disc Assemblies - Tail Rotor Driveshaft | 12/2007 DM |\n| -------------- | --------------------------------------- | ---------- |\n\n| Applicability: | Bell Helicopter Textron Canada (BHTC) Model 407 helicopters S/N up to 53709, 53711 through 53716, 53718 and 53720 through 53722 fitted with disc assemblies part number (P/N) 407-340-340-103.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Verify disc assemblies P/N 407-340-340-103 for manufacturing date, proper thickness and indexing, in accordance with the instructions provided in BHTC Alert Service Bulletin (ASB) ASB-407-07-76 dated 28 March 2007 or later approved revisions.If disc assemblies, after verification in accordance with Requirement 1, do not require any further action, or if the manufacturing date is not between 01 November 2005 and 30 November 2006, make an appropriate log book entry to this effect. No further action is required.2. Remove any disc assembly which is not within the required thickness of 0.115 - 0.127 inch (2.921 - 3.225 mm).3. Remove any disc assembly which is not properly indexed.4. Do not install any disc assembly P/N 407-340-340-103 into any helicopter unless it is compliant to the ASB-407-07-76 dated 28 March 2007 or later approved revisions.Note: Transport Canada Airworthiness Directive CF-2007-14 dated 24 August 2007 refers. |\n| Compliance:    | 1. Unless already accomplished, no later than 25 flight hours or 30 days from the effective date of this directive, whichever comes first.2. Within 10 flight hours, after the completion of requirement 1.3. Within 300 flight hours or at next scheduled inspection, whichever comes first, after the completion of requirement 1.4. After the effective date of this Airworthiness Directive.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n|                | This Airworthiness Directive becomes effective on 3 October 2007.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |\n\n| Background: | Transport Canada has determined that disc assemblies part number (P/N) 407-340-340-103 manufactured between 1 November 2005 and 30 November 2006, may have discs of improper thickness or discs may have been indexed incorrectly. |\n| ----------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n28 September 2007","sortOrder":0},{"sectionNumber":"AD/BELL 407/31","sectionType":"part","heading":"AD/BELL 407/31","content":"## AD/BELL 407/31","sortOrder":1},{"sectionNumber":"Disc Assemblies - Tail Rotor Driveshaft","sectionType":"part","heading":"Disc Assemblies - Tail Rotor Driveshaft","content":"## Disc Assemblies - Tail Rotor Driveshaft","sortOrder":2},{"sectionNumber":"12/2007 DM","sectionType":"part","heading":"12/2007 DM","content":"## 12/2007 DM","sortOrder":3}],"analysis":{"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":3,"scope_assessment":{"changed":false,"description":"The directive confines action to Bell 407 helicopters identified by serial number fitted with disc assembly P/N 407-340-340-103 and to parts manufactured between 1 Nov 2005 and 30 Nov 2006 (Applicability; Background). It mandates inspection, removal if outside thickness or improperly indexed, and prohibits installation unless compliant with the referenced BHTC ASB (Requirements; Compliance). It does not expand applicability beyond those parts/serial numbers or impose broader airworthiness restrictions."},"complexity_factors":["Narrow applicability tied to specific helicopter serial numbers and a single part number (Applicability).","Numeric tolerance requirement for disc thickness (0.115–0.127 inch) that requires measurement equipment and verification (Requirement 2).","Requirement to verify correct indexing, a procedural/assembly check that may need specialist knowledge (Requirement 3).","Multiple compliance timeframes with short windows (25 flight hours/30 days; 10 flight hours; 300 flight hours/next inspection) increasing scheduling complexity (Compliance).","Dependence on external manufacturer document (BHTC ASB ASB-407-07-76) as the compliance method, creating reliance on that bulletin’s procedural detail (Requirement 1 and Requirement 4).","Prohibition on installing non‑compliant parts and logbook entry obligations, which create traceability and record-keeping burdens (Requirements 1 and 4)."],"plain_english_summary":"This directive requires operators of specified Bell 407 helicopters fitted with disc assembly P/N 407-340-340-103 to inspect those assemblies for manufacture date, correct thickness (0.115–0.127 inch) and correct indexing, and to remove any assemblies that fail. It targets parts manufactured between 1 Nov 2005 and 30 Nov 2006 and applies to listed serial-numbered helicopters. It matters because non‑compliant discs must be removed and replacements only installed if they meet the service bulletin’s compliance criteria, creating inspection, maintenance and parts‑replacement costs and scheduling requirements."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive with a focused, narrow scope. It addresses a specific manufacturing defect in a specific part during a specific time period. There is no indication of scope creep; the directive remains tightly targeted at the identified safety issue with the disc assemblies."},"complexity_factors":["Multiple serial number ranges with gaps (53709, then 53711-53716, then 53718, then 53720-53722) requiring careful parsing","Four separate compliance deadlines tied to different requirements and trigger events (effective date, completion of requirement 1)","Specific measurement tolerances in both imperial (0.115-0.127 inch) and metric (2.921-3.225 mm) units","Cross-reference to external document (BHTC Alert Service Bulletin ASB-407-07-76) which contains the actual inspection instructions","Conditional logic: different actions depending on manufacturing date and inspection results","Note referencing related Canadian directive (Transport Canada CF-2007-14) for additional context"],"plain_english_summary":"This AD orders owners/operators of specified Bell 407 helicopters (S/N up to 53709, plus 53711–53716, 53718, 53720–53722) fitted with tail-rotor disc assembly P/N 407-340-340-103 to inspect discs made Nov 2005–Nov 2006 for incorrect thickness or improper indexing and to log results.\n\nInspections are required within 25 flight hours or 30 days; thin discs must be removed within 10 flight hours, improperly indexed discs by 300 flight hours or at next inspection. This prevents tail-rotor failure and loss of control."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-407-31-disc-assemblies-tail-rotor-driveshaft","history":"/api/acts/ad-bell-407-31-disc-assemblies-tail-rotor-driveshaft/history","analysis":"/api/acts/ad-bell-407-31-disc-assemblies-tail-rotor-driveshaft/analysis","conflicts":"/api/acts/ad-bell-407-31-disc-assemblies-tail-rotor-driveshaft/conflicts","importantCases":"/api/acts/ad-bell-407-31-disc-assemblies-tail-rotor-driveshaft/important-cases","documents":"/api/acts/ad-bell-407-31-disc-assemblies-tail-rotor-driveshaft/documents"}}