As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU HAD AUTO SHUTDOWN ON TAXI. APU REPLACED IN ATL. APU S/N P-5745 RECEIVED IN DEPT. 286 9/18/06. INITIAL VISUAL INSPECTION REVEALED 1ST STAGE TURBINE WHEEL FAILURE, WITH PIECE OF MATERIAL EXITING TURBINE BEARING HOUSING AT 10 O'CLOCK POSITION. TURBINE FAILURE DUE TO 1ST STAGE TURBINE WHEEL POST SEPARATION. NO DAMAGE TO APU WELL ON AIRCRAFT.