COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Auxiliary Power Units AD/APU/8 Garrett APU Compressor Rotating Group 4/93 Applicability: Garrett Model GTCP 36-300,-280[B] and -280[D] Requirement: Action in accordance with Garrett Service Bulletins: A. For the GTCP36-300, GTCP36-49-A6642 1 May 1992. B. For the GTCP36-280, GTCP36-49-A6653 1 May 1992. Note: FAA AD 92-21-05 refers. Compliance: To be completed by 30 September 1995. Background: There have been two incidents in which rim separation in the dampening groove of the load compressor has resulted in rotating group unbalance severe enough to cause tieshaft failure just aft of the compressor shaft. The resultant translational energy caused the compressor shafts to exit the APU inlet plenum and penetrate the aircraft firewall. This directive involves rework of the load and engine compressors and replacement of the compressor shaft.