What was found
NR 1 GENERATOR INOPERATIVE AND ON (MEL), APU AUTO SHUTDOWN AT 330 FT, ATTEMPTED 1 RESTART, NO LUCK, DIVERTED & LANDED WITHOUT FURTHER EVENT. MAINT R & R NR 1 IDG, OPS CHK GOOD. MAINT FOUND APU BEARINGS GRINDING & DAMAGE TO BLADES, R & R APU, OPS CHECK GOOD. INCOMING TEST & VISUAL INSPECT OF IDG COULD NOT VERIFY REASON FOR REMOVAL, UNIT DISASSEMBLED & INSPECTED, NO DISCREP NOTED, REPLACED SPEED SENSOR. CONFIRMED FAILURE OF APU TURBINE SECTION DAMAGE. PRIMARY CAUSE OF DAMAGE DUE TO TURBINE WHEEL SHAFT SEPARATION; THIS CAUSED SECONDARY DAMAGE TO LOAD COMP & COMP IMPELLERS. INLET GUIDE VANES, COMP DIFFUSERS, & TURBINE NOZZLE DAMAGED BY CONTACT WITH CENTER SHAFT. UNIT REPAIRED, TESTED, & RETURNED TO SERVICE.