AD/Bell 206/175 Engine Power Turbine Speed Limitations (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 206/175 Engine - Power Turbine Speed Limitations 4/2009 TX

Applicability:

Agusta S.p.A. AB206B and AB206A helicopters converted into AB206B as per Agusta Bollettino Tecnico (BT) 206-52, all serial numbers if equipped with Rolls-Royce Corporation (formerly Allison) engine model 250-C20, 250-C20B, 250-C20J, and 250-C20R/4.

Requirement:

1.    Determine the part number (P/N) of the installed third stage turbine wheel.

2.    If the third stage turbine wheel is P/N 23065818, proceed with the following instructions, otherwise no further action is required by this AD.

3.    Insert page 5 or 6 (as applicable depending on the helicopter model) of Agusta BT 206-244 with the turbine speed limitation in the applicable Flight Manual - Section I Limitations, paragraph “POWER PLANT LIMITATIONS”.

4.    Install the decal “AVOID OPS 75% TO 88% N2 WITH TQ ABOVE 30%” on the instruments panel below the power turbine indicator.

5.    If the transient time in the N2 range between 75% and 88% with engine torque above 30% exceeds 60 seconds for a single or multiple events, perform the specific corrective actions as per Rolls-Royce Commercial Engine Bulletin (CEB) A-1400 Rev. 3.

The use of later approved revisions of the documents detailed in this AD is acceptable for compliance with the requirements of this AD.

Note:  EASA Emergency AD 2009-0022-E dated 6 February 2009 refers.

Compliance:

For Requirements 1 through 4 - Within the next 5 flight hours after the effective date of this directive but no later than 25 February 2009, whichever occurs first, unless previously accomplished.

For Requirement 5 - Before further flight.

This Airworthiness Directive becomes effective on 20 February 2009.

Background:

Following several third stage turbine wheel failures, the engine Type Certificate holder, Rolls-Royce Corporation, issued Commercial Engine Bulletin (CEB) A-1400 Rev. 3 to introduce an operational limitation on the power turbine N2 speed range (75% - 88%).

Thereafter, Agusta issued Alert BT 206-244 to introduce the same operating limitation, which is also required by this AD, on the affected helicopters.

James Coyne
Delegate of the Civil Aviation Safety Authority

16 February 2009