Ad/Bell 206/161 - Power Turbine RPM Steady State Operation (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Bell Helicopter Textron Canada (BHTC) 206 and Agusta Bell 206 Series Helicopters

AD/BELL 206/161 Power Turbine RPM Steady
State Operation 11/2005

Applicability:

Bell Helicopter Textron Canada (BHTC) Model 206L-3 serial numbers 51001 through 51612, and 206L-4 helicopters serial numbers 52001 through 52313.

Requirement:

1.    Insert the appropriate flight manual revisions, BHT-206L3-FM-1, Revision 6, dated 26 April 2005, or BHT-206L4-FM-1, Revision 6, dated 26 April 2005, or later Transport Canada approved revisions, into the rotorcraft flight manual and advise the pilot of this change.

2.    Install the decal as per Alert Service Bulletin 206L-05-134, dated 8 June 2005, or later Transport Canada revisions.  It is permissible to locally manufacture the decal with white lettering on a black background, minimum 10 point font size.

Note:  Transport Canada AD CF-2005-28 refers.

Compliance:

Within 10 calendar days after the effective date of this directive.

This Airworthiness Directive becomes effective on 27 October 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 eight in-flight failures reported.  Rolls-Royce has determined that detrimental vibrations can occur within a particular range of turbine speed as a potential contributing factor to these failures.  BHTC revised their rotorcraft flight manual and provided a decal to inform pilots to avoid steady state operations at these engine turbine speeds.

James Coyne
Delegate of the Civil Aviation Safety Authority

16 September 2005