AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/DART/29 Amdt 1 and issues the following AD under subregulation 39.1 (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. Rolls Royce Turbine Engines - Dart Series AD/DART/29 Amdt 2 High Pressure Turbine Discs 10/2003 Applicability: Rolls Royce Dart series engines as detailed by model in Rolls Royce Service Bulletin (SB) Da72-533, Revision 2 and not incorporating modification 1946 (SB Da72-533). Requirement: 1. Replace or rework affected high pressure turbine (HPT) discs in accordance with the procedure detailed in Rolls Royce SB Da72-533 Revision 2; OR 2. As considered appropriate by the operator, carry out a once-only inspection in accordance with Rolls Royce SB Da72-536. As provided in German LBA AD 2001-116/6 and Rolls Royce SB Da72-536 a satisfactory inspection result allows an extension to the interim compliance times of Rolls Royce SB Da72-533 of 750 flight cycles from the date of inspection but not beyond 30 June 2004. Such an extension to the interim compliance times of Rolls Royce SB Da72-533 may not be used unless a satisfactory inspection has been carried out in accordance with Rolls Royce SB Da72-536. Note: German LBA AD 2001-116/6 refers. Compliance: For Requirement 1: As detailed in the Requirement document. For Requirement 2: As contained in the Requirement. This Amendment becomes effective on 2 October 2003. Background: This Directive was originally issued to address in-service failures of HPT disc diaphragms that resulted in three events of the HPT disc release. The failures were attributed to 2D excitation of the HPT assembly as a result of frettage between HPT disc and Intermediate Pressure Turbine (IPT) disc seal arms. Amendment 1 was issued to reflect the manufacture's latest revision to the requirement document that included, in part, a drawdown programme for HPT discs not incorporating modification 1946. This revision recognises German LBA AD 2001-116/6 as the authority document for the AD and thereby introduces an NDT inspection that if satisfactory provides for an extension to the compliance times contained in RR SB Da72-533. Rolls Royce Turbine Engines - Dart Series AD/DART/29 Amdt 2 (continued) Amendment 1 of this Airworthiness Directive became effective on 4 October 2001. The original issue of this Airworthiness Directive became effective on 12 July 2001. Jim Coyne Delegate of the Civil Aviation Safety Authority 19 August 2003 The above AD is notified in the Commonwealth of Australia Gazette on 10 September 2003.