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. Allison Turbine Engines - 250 Series AD/AL 250/83 Third-Stage Turbine Wheels 10/2004 Applicability: Rolls-Royce Corporation (formerly Allison Engine Company), models 250-C28, - C28B, and -C28C turboshaft engines with third-stage turbine wheels, part number (P/N) 6899383, listed by serial number (SN) in Table 1 of this Directive: Table 1. - SNs of Affected Third Stage Turbine Wheels HX91922 X523242 X523281 HX91923 X523243 X523283 HX91925 X523244 X523284 HX91926 X523246 X523287 HX91928 X523249 X523288 HX91929 X523250 X523289 HX91930 X523251 X523290 HX91932 X523253 X523291 HX91934 X523255 X523292 HX91936 X523257 X523293 HX91937 X523260 X523294 HX91939 X523261 X523295 HX91940 X523262 X523296 HX91960 X523263 X523297 HX91962 X523264 X523298 HX91966 X523265 X523300 HX91976 X523266 X523305 HX91977 X523268 X523309 HX91979 X523269 X523313 HX91980 X523270 X523315 X523236 X523271 X523317 X523237 X523273 X523319 X523238 X523276 X523320 X523239 X523277 X523241 X523278 Note 1: These engines are installed on, but not limited to, Bell Helicopter Textron 206L-1; Eurocopter Deutschland BO 105 LS A-1; and Eurocopter Canada BO 105 LS A-3 helicopters. Requirement: 1. Replace the third-stage turbine wheel with a turbine wheel not listed in Table 1 of this Directive. 2. Do not install third- stage turbine wheels that are listed in Table 1 of this AD, into any engine. Note 2: FAA AD 2004-14-02 Amdt 39-13711 refers. Compliance: For Requirement 1: For third-stage turbine wheels with less than 250 operating hours' time since new (TSN) on the effective date of this Directive, before accumulating 300 operating hours TSN. For any third-stage turbine wheel with 250 or more operating hours TSN on the effective date of this Directive, before accumulating an additional 50 operating hours. For Requirement 2: From the effective date of this Directive. This Airworthiness Directive becomes effective on 30 September 2004. Background: This Directive results from three reports of third-stage turbine wheel blade and shroud failures. The issue of this Directive is to prevent loss of power and uncommanded engine shutdown due to failure of the third-stage turbine wheel blade and shroud. Gary J Carr Delegate of the Civil Aviation Safety Authority 5 August 2004 The above AD is notified in the Commonwealth of Australia Gazette on 8 September 2004.