{"id":"F2007L03909","name":"AD/BELL 206/173 - Disc Assemblies - Tail Rotor Driveshaft","slug":"ad-bell-206-173-disc-assemblies-tail-rotor-driveshaft","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":70553,"registerId":"commonwealth-F2007L03909-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Bell Helicopter Textron Canada (BHTC) 20","sectionType":"division","heading":"Bell Helicopter Textron Canada (BHTC) 206 and Agusta Bell 206 Series Helicopters","content":"### Bell Helicopter Textron Canada (BHTC) 206 and Agusta Bell 206 Series Helicopters\n\n| AD/BELL 206/173 | Disc Assemblies - Tail Rotor Driveshaft | 12/2007 DM |\n| --------------- | --------------------------------------- | ---------- |\n\n| Applicability: | Bell Helicopter Textron Canada (BHTC) Model 206 series helicopters S/N up to 4618 and Model 206L series helicopters S/N up to 52340 fitted with disc assemblies P/N 32721-1.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Verify disc assemblies P/N 32721-1 for manufacturing date, proper thickness and indexing, in accordance with the instructions provided in the applicable Alert Service Bulletins (ASB) listed below or later approved revisions.206 series: ASB-206-07-114 dated 28 March 2007206L series: ASB-206L-07-145 dated 28 March 2007If disc assemblies, after verification in accordance with Requirement 1, do not require any further action, or if the manufacturing date is not between 1 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 32721-1 into any helicopter unless it is compliant to the applicable Alert Service Bulletins (ASB) listed below or later approved revisions.206 series: ASB-206-07-114 dated 28 March 2007.206L series: ASB-206L-07-145 dated 28 March 2007.Note: Transport Canada Airworthiness Directive CF-2007-16 dated 24 August 2007 refers. |\n\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| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n|             | This Airworthiness Directive becomes effective on 3 October 2007.                                                                                                                                                                                                                                                                                                                                |\n| Background: | Transport Canada has determined that disc assemblies part number (P/N) 32721-1 manufactured between 1 November 2005 and 30 November 2006, may have discs of improper thickness or discs may have been indexed incorrectly.                                                                                                                                                                       |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n28 September 2007","sortOrder":0},{"sectionNumber":"AD/BELL 206/173","sectionType":"part","heading":"AD/BELL 206/173","content":"## AD/BELL 206/173","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":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive targets the cohort identified in its Background — disc assemblies P/N 32721-1 (manufactured 1 Nov 2005–30 Nov 2006) on specified Bell 206/206L serial numbers — and prescribes inspection, removal and installation controls. It does not expand beyond that set of helicopters or parts described in the Background and Applicability sections."},"complexity_factors":["Technical measurement requirement — strict thickness tolerance 0.115–0.127 inch (Requirement 2)","Indexing verification — a correctness check that may require technical judgement or tooling (Requirement 3)","Reliance on external documents — requires following specific Alert Service Bulletins and later approved revisions (Requirements 1 and 4)","Multiple, staggered compliance timeframes — 25 flight hours/30 days; 10 flight hours; 300 flight hours/next inspection (Compliance)","Applicability limited by serial number ranges and part number, requiring parts / records review (Applicability)","Mandatory logbook entry when no action required, creating an administrative compliance step (Requirement 1)","Prohibition on installing non-compliant parts, creating parts-control and supply implications for operators (Requirement 4)","Cross-reference to another regulator's AD (Transport Canada CF-2007-16), which may affect interpretive or remedial options (Note/Background)","Potential operational impact — inspection/removal can cause aircraft downtime and replacement part demand (implicit cost/incentive effect)"],"plain_english_summary":"This Airworthiness Directive requires operators of specified Bell 206/206L helicopters fitted with disc assembly P/N 32721-1 to inspect parts per the cited Alert Service Bulletins for manufacture date, thickness (0.115–0.127 in) and correct indexing, remove non-conforming units, and record the outcome; only ASB‑compliant parts may be installed (Requirements 1–4; Compliance). Operators bear inspection, replacement and downtime costs; the regulator enforces short compliance windows (e.g. 25 flight hours/30 days)."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific manufacturing defect in a single part number (P/N 32721-1) for specific helicopter models. The requirements remain tightly focused on inspection and replacement of the defective disc assemblies without expanding to unrelated systems or broader operational restrictions."},"complexity_factors":["Single, specific mechanical defect addressed (manufacturing error in one part number)","Clear applicability criteria (specific serial number ranges and part number)","Straightforward conditional logic: IF manufactured in date range AND fails thickness/indexing test THEN remove","Multiple compliance deadlines but clearly tiered (immediate, 10 hours, 300 hours)","Only 2 cross-referenced documents (the Alert Service Bulletins)","No nested definitions or interpretation sections","Background explanation provided in plain language"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of certain Bell 206/206L helicopters (specific serial ranges) fitted with disc assembly P/N 32721‑1 manufactured Nov 2005–Nov 2006 to inspect and, if out-of-tolerance or mis‑indexed, remove and not reinstall the affected tail‑rotor driveshaft discs. It mandates prompt checks, removal of defective parts, an installation ban, and logbook entry to prevent tail‑rotor failure and potential loss of control."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-206-173-disc-assemblies-tail-rotor-driveshaft","history":"/api/acts/ad-bell-206-173-disc-assemblies-tail-rotor-driveshaft/history","analysis":"/api/acts/ad-bell-206-173-disc-assemblies-tail-rotor-driveshaft/analysis","conflicts":"/api/acts/ad-bell-206-173-disc-assemblies-tail-rotor-driveshaft/conflicts","importantCases":"/api/acts/ad-bell-206-173-disc-assemblies-tail-rotor-driveshaft/important-cases","documents":"/api/acts/ad-bell-206-173-disc-assemblies-tail-rotor-driveshaft/documents"}}