{"id":"F2005L02430","name":"AD/BELL 407/27 Amdt 1 - Power Turbine RPM Steady State Operation Avoidance","slug":"ad-bell-407-27-amdt-1-power-turbine-rpm-steady-state-operation-avoidance","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":36978,"registerId":"commonwealth-F2005L02430-current","compilationNumber":null,"startDate":"2026-04-01","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 407/27 Amdt 1 | Power Turbine RPM SteadyState Operation Avoidance | 10/2005 |\n| --------------------- | ------------------------------------------------- | ------- |\n\n| Applicability: | Bell Helicopter Textron Canada (BHTC) Model 407 helicopters, serial numbers 53000 to 53644.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Flight Manual AmendmentUnless previously accomplished incorporate BHT-407-FM-1 Revision 3 or later Transport Canada approved revision into the rotorcraft flight manual.2. Installation of DecalUnless previously accomplished, install the decal as per Alert Service Bulletin 407-05-67, dated 8 June 2005, or later Transport Canada approved revision. It is permissible to locally manufacture the decal with white lettering on a black background, minimum 10 point font size.Requirements 1 and 2 may be accomplished by a pilot endorsed on the Bell 407.Note: Transport Canada AD CF-2004-09R1 refers.                   |\n| Compliance:    | Within 10 calendar days after the effective date of this directive.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n|                | This Amendment becomes effective on 29 September 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |\n| Background:    | Transport Canada has been advised of multiple reports of failure of the third stage turbine wheel used in both the Rolls-Royce 250-C30S and 250-C47B engines. There have been six in-flight failures of which three have occurred to the 250-C47B engine utilized by BHTC for the Model 407. Rolls Royce has determined that detrimental vibrations occurring at power turbine speeds between 68% and 86% may be a potential contributing factor to these failures.This amendment introduces a slight increase to the steady-state operation avoidance limitations, and includes additional helicopters in the applicability section. |\n\n|     | The original issue of this Directive became effective 30 September 2004. |\n| --- | ------------------------------------------------------------------------ |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n18 August 2005","sortOrder":0},{"sectionNumber":"AD/BELL 407/27 Amdt 1","sectionType":"part","heading":"AD/BELL 407/27 Amdt 1","content":"## AD/BELL 407/27 Amdt 1","sortOrder":1},{"sectionNumber":"Power Turbine RPM SteadyState Operation ","sectionType":"part","heading":"Power Turbine RPM SteadyState Operation Avoidance","content":"## Power Turbine RPM Steady  \nState Operation Avoidance","sortOrder":2},{"sectionNumber":"10/2005","sectionType":"part","heading":"10/2005","content":"## 10/2005","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":2,"scope_assessment":{"changed":true,"description":"This amendment slightly increases the steady‑state power turbine RPM avoidance limitations and expands the applicability to additional helicopters (Background: \"introduces a slight increase to the steady‑state operation avoidance limitations, and includes additional helicopters in the applicability section\")."},"complexity_factors":["Narrow applicability by serial number: Model 407 helicopters, s/n 53000–53644 (Applicability).","Two discrete, simple compliance actions: flight manual amendment and decal installation (Requirement).","Short mandatory compliance timeframe: within 10 calendar days of effective date (Compliance).","Allows pilot performance of actions, lowering need for maintenance resources (Requirement: \"may be accomplished by a pilot endorsed on the Bell 407\").","Permits local manufacture of decal with minimal specifications (Requirement), reducing logistical burden.","Operational constraint stems from engine vibration concerns at specific power turbine speeds (Background: 68%–86% identified by Rolls‑Royce).","Cross‑reference to Transport Canada AD CF‑2004‑09R1 and earlier directive history adds minor interpretive linkage (Background; original issue effective 30 Sept 2004)."],"plain_english_summary":"Requires Bell 407 helicopters (serial numbers 53000–53644) to incorporate a revised flight manual entry and to install a cockpit decal advising avoidance of steady‑state power turbine speeds linked to failures. Transport Canada ties the restriction to third‑stage turbine wheel failures associated with vibrations in a specific RPM band. Operators must comply within 10 calendar days; a pilot endorsed on the Bell 407 may carry out the actions."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"This Amendment 1 expands the scope compared to the original September 2004 directive. The background explicitly states it 'includes additional helicopters in the applicability section' and introduces 'a slight increase to the steady-state operation avoidance limitations' (expanding the restricted RPM range from the original directive)."},"complexity_factors":["Very short document (approximately 300 words)","Only 2 substantive requirements (flight manual amendment + decal installation)","Single interpretation section with no defined terms","No cross-references to other legislation or regulations","Simple conditional logic ('unless previously accomplished')","Clear, unambiguous compliance deadline (10 calendar days)"],"plain_english_summary":"This CASA Airworthiness Directive mandates owners/operators of Bell 407 helicopters (S/N 53000–53644) update their flight manuals and install a cockpit warning decal to avoid power turbine speeds between 68% and 86%. It responds to multiple Rolls‑Royce turbine‑wheel failures linked to harmful vibrations in that speed band. The change broadens the restricted range and adds more helicopters to the original 2004 order; suitably endorsed pilots may perform the manual and decal updates themselves."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-407-27-amdt-1-power-turbine-rpm-steady-state-operation-avoidance","history":"/api/acts/ad-bell-407-27-amdt-1-power-turbine-rpm-steady-state-operation-avoidance/history","analysis":"/api/acts/ad-bell-407-27-amdt-1-power-turbine-rpm-steady-state-operation-avoidance/analysis","conflicts":"/api/acts/ad-bell-407-27-amdt-1-power-turbine-rpm-steady-state-operation-avoidance/conflicts","importantCases":"/api/acts/ad-bell-407-27-amdt-1-power-turbine-rpm-steady-state-operation-avoidance/important-cases","documents":"/api/acts/ad-bell-407-27-amdt-1-power-turbine-rpm-steady-state-operation-avoidance/documents"}}