What was found
APU FIRE/OVHT LIGHT ILLUMINATED IN FLIGHT. QRH/MEMORY ITEMS FOLLOWED, BOTTLE DISCHARGED, FIRE/OVHT LIGHT EXTINGUISHED. INSPECTION FOUND HEAT DAMAGE TO OVHT/FIRE DETECTION WIRING AND POSSIBLE TURBINE WHEEL FAILURE. REMOVED AND REPLACED APU. FAILURE ANALYSIS - PROBABLE CAUSES ARE DEFECTIVE TEMPERATURE CONTROL SYS/ INCORRECT TURBINE BEARING SLEEVE INSTALLED, WHICH WOULD RESULT IN EXCESSIVE VIBRATION FOLLOWED BY CONTACT OF THE TURBINE WHEEL AND SHROUD. (K)