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AD/BELL 407/27 Amdt 1 - Power Turbine RPM Steady State Operation Avoidance
Bell Helicopter Textron Canada (BHTC) 40Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters
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Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters
| AD/BELL 407/27 Amdt 1 | Power Turbine RPM SteadyState Operation Avoidance | 10/2005 |
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| Applicability: | Bell Helicopter Textron Canada (BHTC) Model 407 helicopters, serial numbers 53000 to 53644. |
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| 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. |
| Compliance: | Within 10 calendar days after the effective date of this directive. |
| This Amendment becomes effective on 29 September 2005. | |
| 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. |
| The original issue of this Directive became effective 30 September 2004. |
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James Coyne
Delegate of the Civil Aviation Safety Authority
18 August 2005