What was found
(CAN) DURING START AT 16 PERCENT, PILOT HEARD A LOUD BANG. THE FUEL FLOW WAS GOOD, TEMP AT 410 CELSIUS. THEN A SECOND BANG AND TEMP AT 700 CELSIUS (MAX IS 570 CELSIUS). ENGINE WAS SHUTDOWN. INSPECTION FOUND LP TURBINE BLADES DEFORMED WITH PIECES OF STAGE 2 BLADES LOCATED BETWEEN THE LP2 TURBINE AND MIXER. DEBRIS FOUND IN REAR BYPASS DUCT. STAGE 1 TURBINE BLADES SHOWED VIRTUALLY NO DAMAGE, BOTH STAGE 1 AND 2 NOZZLE GUIDE VANES SHOWED HEAVY DAMAGE. THERE WAS NO METAL IN THE FILTER. LAB ANALYSIS SHOWED SEVERE STRUCTURAL CHANGE OF STAGE 1 TURBINE BLADES INDICATIVE OF SEVERE OVERHEAT CONDITION. INVESTIGATION CONTINUES INTO CAUSE OF THE FAILURE.