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/TFE731/17 L.P. Turbine Third Stage Rotor Disc 7/89 DM Applicability: TFE 731 series engines which may have suspect L.P. turbine third stage rotor disc part number 3074756-1/-2 whose serial numbers are listed in the Requirement document. Requirement: Remove from service specific serial numbered L.P. turbine third stage rotor disc P/N 3074756-1/-2 (part of rotor assy P/N 3074757-1) whose serial numbers are listed in Table 1 of Allied Signals (Garrett) S.B. TFE 731-72-3387. Compliance: Unless already accomplished, within 100 hours time in service after 10 May 1989. Background: The manufacturer, in Service Bulletin TFE 731-72-3387, has advised that specific S/No L.P. third stage turbine discs have been manufactured with the outside diameter 0.020 inch oversize. The inspection, rework and reidentification of oversize disc assemblies can be accomplished by fitting shorter blades. This Directive is issued to ensure that suspect assemblies are removed in a timely manner to prevent turbine failures occurring.