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. Rolls Royce (Allison) Turbine Engines - AL501 Series AD/AL501/3 First Stage Turbine Wheels 6/2006 Applicability: Rolls Royce (formerly DETROIT DIESEL ALLISON) Model 501-D13, 501-D13A, 501-D13D, 501-D13E, and 501-D13H engines equipped with 1st stage turbine wheels with part numbers 6844061 and 6847111. Requirement: Remove from service first stage turbine wheels in accordance with the schedule detailed in FAA AD 80-14-13. Note: FAA AD 80-14-13 Amdt 39-3820 refers. Compliance: As detailed in FAA AD 80-14-13 with a revised effective date of 8 June 2006. This Airworthiness Directive becomes effective on 8 June 2006. Background: This AD is intended to prevent disc failures due to fatigue. The schedule for removal is based upon the dimension of the spline fit. James Coyne Delegate of the Civil Aviation Safety Authority 28 April 2006