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. Allison Turbine Engines - 250 Series AD/AL 250/87 Containment Ring 8/2005 Applicability: Rolls-Royce Corporation (RRC) (formerly Allison Engine Company) 250-B17B, -B17C, -B17D, -B17E, -C20, -C20B, -C20F, -C20J, -C20S and -C20W turboprop and turboshaft engines that do not have turbine energy absorbing ring part number (P/N) 23035175, or an equivalent approved serviceable turbine energy absorbing ring installed. Requirement: Unless previously accomplished, install a turbine energy absorbing ring, RRC P/N 23035175, or an equivalent approved turbine energy absorbing ring, in the plane of the 1st stage turbine wheel, using paragraphs 1.M., 2.A. and 2.B. of Rolls-Royce Corporation Alert Commercial Engine Bulletin No. CEB-A-1255, Revision 4 dated 29 September 2004 to do the installation. Note: FAA AD 2005-10-13Amdt 39-14090 refers. Compliance: At the next time the gas producer turbine rotor is disassembled for any reason, or within 1,750 hours time-since-last overhaul, time since-new, time-since-last-heavy-maintenance, or time-since-last-hot section inspection after the effective date of this Directive, whichever occurs first, but no later than 31 October 2011. This Airworthiness Directive becomes effective on 4 August 2005. Background: This Directive is in response to an unacceptable rate of uncontained 1st stage turbine wheel failures. The fitment of the energy absorbing ring is designed to minimize the risk of uncontained 1st stage turbine wheel fragments from causing damage to the aircraft, which could lead to loss of control and loss of the aircraft. James Coyne Delegate of the Civil Aviation Safety Authority 24 June 2005