What was found
CUSTOMER REPORTED APU FAILURE, SUDDEN STOPPAGE, AND GEARBOX FAILURE. ACFT WAS ON GROUND AND APU IDLE, NOT LOADED. APU SUSTAINED A POWER GROUP CONTAINED SEPARATION FAILURE AND UNCONTAINED GEARBOX FAILURE. TEARDOWN REVEALED COMPRESSOR ROTOR FAILURE, VANE PLATFORM CRACKED, AND FRACTURED COMPRESSOR ROTOR, PN 3822014-2 SN 9-19412-1081, PART TSN 6585 HRS, APU TSN 6585 HRS, MFG DATE 11-14-80. COMPRESSOR ROTOR MENTIONED PN 3822014-2 IS LIFE LIMITED TO 10,000 HRS/CYCLES IAW SIL APU-56 AND MM NR 49-21-59 REV 13. SUBMITTER RECOMMENDED LIFE LIMIT REDUCED TO 3,000 TO 5,000 HRS/CYCLES. (X)