COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Williams-Rolls Turbine Engines - FJ44 Series AD/FJ44/1 High Pressure Turbine Disc 5/97 Applicability: FJ44-1A engines as detailed by serial number in Williams-Rolls Service Bulletin (SB) Number FJ44-A72-30 and not incorporating a part number (P/N) 55291 high pressure turbine disc. Requirement: To prevent a possible high pressure turbine (HPT) disc blade retention post separation and the release of turbine blades event, carry out an initial and repetitive eddy current inspection of the P/N 48629 HPT disc in accordance with the requirements of Williams-Rolls SB No. FJ44-A72-30. Note 1: FAA Airworthiness Directive 97-01-05 refers. Note 2: Compliance with Williams-Rolls SB No. FJ44-A72-31 constitutes a terminating action for the requirements of this directive. Compliance: As detailed in the requirement document with a revised effective date of 24 April 1997. This Airworthiness Directive becomes effective on 24 April 1997. Background: This directive has been issued to require the inspection of certain HPT discs for evidence of cracking in the blade retention posts. The requirement reflects advice of two in-flight HPT disc blade post separation events involving the Williams-Rolls FJ44 engine. One of the events was uncontained. An investigation of the events revealed in both cases, the HPT blade retention posts separated through cracking caused by material creep/fatigue.