COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES 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 39.1 (1) of CAR 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. Turbomeca Turbine Engines - Arriel Series AD/ARRIEL/15 Centrifugal Impeller 6/2002 Applicability: All Arriel 2 turboshaft engines. Requirement: 1. Carry out installation of a sleeve in the bleed valve boss as described in Turbomeca Service Bulletin (SB) No. 292 72 2054. 2. Carry out bonding of sleeve in the bleed valve boss as described in Turbomeca SB No. 292 72 2070 Update 1. Note: DGAC AD 2002-127(A) refers. Compliance: Unless previously accomplished; within 100 hours time in service or prior to 31 July 2002, whichever occurs first. This Airworthiness Directive becomes effective on 13 June 2002. Background: Several contained centrifugal impeller blade ruptures have been observed in service. These failures led to a power loss but could have led to non commanded in-flight shutdowns. Investigations revealed that acoustic excitation was the cause of the failures. The excitation caused by coupling that may occur between the impeller blades and the acoustic cavity. Incorporation of SB No. 292 72 2054 and SB No. 292 72 2070 will suppress this excitation. James Coyne Delegate of the Civil Aviation Safety Authority 12 April 2002 The above AD is notified in the Commonwealth of Australia Gazette on 22 May 2002. Page 1 of 1