AD/Bell 206/172 Power Turbine RPM Steady State Operation Avoidance (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 206/172 Power Turbine RPM Steady State
Operation Avoidance 12/2007 DM

Applicability:

Bell Helicopter Textron Canada (BHTC) Model 206B series helicopters including those converted from model 206A, serial numbers up to 4366, and 206L helicopters serial numbers 45004 through 45153 and 46601 through 46617.

Requirement:

1.    Update the applicable Rotorcraft Flight Manuals (RFM) by inserting appropriate RFM revisions dated 2 April 2007 or later approved revisions and advise the pilots of this change:

Model 206B - revision B-48

Model 206B3 - revision 9

Model 206L - revision 26

2.    Install the decal as per Alert Service Bulletin (ASB) 206-07-115 or 206L-07-146, as applicable, dated 21 May 2007, or later approved revisions. 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 with appropriate endorsement.

Note:  Transport Canada Airworthiness Directive CF-2007-13 dated 24 August 2007 refers.

Compliance:

Unless already accomplished, within 10 calendar days after the effective date of this directive.

This Airworthiness Directive becomes effective on 3 October 2007.

Background: Transport Canada has been advised of the failure of third stage turbine wheels used in Rolls-Royce 250-C20 engines.  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 has revised RFMs and provided a decal to inform pilots to avoid steady state operations at these engine turbine speeds.

David Villiers
Delegate of the Civil Aviation Safety Authority

27 September 2007