COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES AlliedSignal (Garrett/AiResearch) Turbine Engines - TFE731 Series AD/TFE731/15 HP Turbine Rotor Disc 12/88 DM Applicability: TFE 731-3 series engines which may have suspect HP turbine rotor discs whose S/No are listed in the Requirement document. Requirement: Remove from service specific serial numbered HP turbine rotor disc Part No. 3072316-2/-3 and 3073110-1/-2 in accordance with GTEC Alert SB TFE 731-A72 - 3376. Note: FAA AD Priority Letter 88-18-03 refers. Compliance: Within 25 engine operating cycles after 22 September 1988. Background: This Directive is issued following advice from the manufacturer that some HP turbine rotor discs have incorrect curvic coupling tooth root fillet radii. This Directive is required to prevent uncontained HP turbine disc failures which could occur on engines containing suspect reworked discs.