What was found
THE PILOT REPORTED A LOUD BANG AT 40K FT. DURING THE NEXT START, AT 15-20 PERCENT N2, THERE WAS A VIBRATION AND START ABORTED. AFTER WAITING 15-20 MINS, ANOTHER START ATTEMPTED, SOME VIBRATIONS AT 40 PERCENT N2, ENGINE STABILIZED. 40 MINS INTO FLT WAS ANOTHER LOUD BANG AND SOME VIBRATIONS FOR 1-2 SECONDS. PAX REPORTED AN FUMES IN CABIN, ALTHOUGH CREW DID NOT NOTICE. FLT CONTINUED WITHOUT INCIDENT. ON NEXT TAKEOFF, ITT WENT INTO AMBER FOR LESS THAN A SECOND. ENGINE RETURNED TO REPAIR STATION AND BORESCOPE INSPECTED UPON RECEIPT WITH NO UNUSUAL FINDING. ENGINE INSTALLED INTO TEST CELL FOR AN "AS RECEIVED" ATP. APPROX 1 HOUR INTO THE ATP, AFTER STABILITY & ACCELERATION CHECKS, ENGINE SURGED NEAR TAKEOFF POWER. DISASSEMBLY OF ENGINE REVEALED A FAILED 2ND STAGE IP BLADE. NO EVIDENCE OF FOREIGN OBJECTS WERE NOTED IN THE DISASSEMBLY PROCESS.