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 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 (Allison) Turbine Engines - AE 2100 Series AD/AE 2100/1 High Pressure Turbine Wheel 7/2004 Applicability: Rolls-Royce Corporation (formerly Allison Engine Company) models AE 2100A and AE 2100C turboprop engines with high pressure turbine (HPT) wheel part number (P/N) 23050912 installed; AE 2100A turboprop engine with turbine wheel P/N 23063462 serial number (SN) MM14062 installed; AE 2100A, AE 2100C, AE 2100D3 turboprop engines with 2nd stage HPT wheels with SN's prior to MM183060. Requirement: 1. Perform a one-time acid etch inspection to the 2nd stage high pressure turbine wheel in accordance with the Accomplishment Instructions contained in the following Rolls-Royce Alert Service Bulletins, Table 1. Table 1. AE models Rolls-Royce service bulletin AE 2100A AE 2100A-A-72-234, Revision 2, dated October 13, 2000 or Revision 3, dated June 19, 2001. AE 2100C AE 2100C-A-72-183, Revision 2, dated October 13, 2000 or Revision 3, dated June 19, 2001. AE 2100D3 AE 2100D3-A-72-179, Revision 2, dated October 13, 2000 or Revision 3, dated June 19, 2001. 2. If damage is discovered, replace the turbine wheel with a serviceable part. 3. Do not install any 2nd-stage gas-generator turbine wheel listed in Table 2 of this Directive, unless it has been inspected as specified in Requirement 1 of this Directive. Note: FAA AD 2001-17-31 Amdt 39-12423 refers. Compliance: For Requirement 1: As detailed in Table 2 of this Directive. Table 2. Models With turbine wheel Mandatory AE 2100A, AE2100C 23050912 Before 4,800 cycles since new (CSN). AE 2100A 23063462-S/N MM14062. Before 4,800 CSN. AE2100D3 23050912 Before 3,200 CSN. All other AE 2100A, AE 2100C and AE2100D3 23063462, 23064822, At next shop visit. 23070673, 23065892, 23069116, 23064473, 23064474, 23068072, 23070672 and 23070675 with S/N's MM183060 and before. All AE 2100A and AE 2100C 23069592 with S/N MM183060 and before. Next exposure but not to exceed 16,800 CSN. All 2100D3 23069592 with S/N MM183060 and before. Next exposure but not to exceed 14,100 CSN. For Requirement 2: Before further flight. For Requirement 3: From the effective date of this Directive. This Airworthiness Directive becomes effective on 8 July 2004. Background: This Directive is prompted by a report of a 2nd stage HPT wheel that was returned from the field with cracks in the aft bore face. The actions specified by this Directive are intended to detect and prevent early development of cracks due to low cycle fatigue of the 2nd stage HPT wheel in the aft bore face that can lead to wheel failure, power loss, and possible damage to the aeroplane. James Coyne Delegate of the Civil Aviation Safety Authority 27 May 2004 The above AD is notified in the Commonwealth of Australia Gazette on 16 June 2004.