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. Auxiliary Power Units AD/APU/16 T-62T APU Compressor Wheel Replacement 11/2002 Applicability: Hamilton Standard Power Systems (formerly Sundstrand Power Systems, Turbomach, and Solar) models T-62T-2C, T-62T-25, T-62T-29 and T-62T-39 Auxiliary Power Units (APU) that have compressor wheel part number 100636-1 installed. Requirement: 1. Replace cast steel (see Note 1) compressor wheels Part Number (P/N) 100636-1 with compressor wheel P/N 4503164, 4504174, or M4504174. 2. Replace wrought steel (see Note 2) compressor wheels P/N 100636-1 with compressor wheel P/N 4503164, 4504174, or M4504174. Note 1: Cast steel compressor wheels are identifiable by a four digit casting lot vendor identification number used as a prefix to the serial number. Note 2: Wrought steel compressor wheel is identifiable by a serial number beginning with the letter "W". Note: FAA AD 2002-15-02, Amdt 39-12830 refers. Compliance: Requirement 1: a. Cycles since new greater than 2.350; within 250 cycles in service (CIS) after the effective date of this directive. b. Cycles since new less than 2,350; prior to 2600 cycles. Requirement 2: a. Cycles since new greater than 3,600; within 500 CIS after the effective date of this directive. b. Cycles since new less than 3,600; prior to 4,100 cycles. This Airworthiness Directive becomes effective on 31 October 2002. Auxiliary Power Units AD/APU/16 (continued) Background: The actions specified in this directive mandates the removal of affected compressor wheels, which if not replaced, could result in uncontained compressor wheel failures and damage to the aeroplane. This directive establishes a life limit of 2,600 cycles for cast steel compressor wheels and a life limit of 4,100 cycles for wrought steel compressor wheels. James Coyne Delegate of the Civil Aviation Safety Authority 24 September 2002 The above AD is notified in the Commonwealth of Australia Gazette on 9 October 2002.