What was found
FLT NR 477 - RDU - THE NR 1 ENGINE COMPRESSOR BEGAN TO STALL AT FL 310 WHILE EN ROUTE FROM EWR TO TPA. THE STALL WAS ACCOMPANIED BY A LOUD BANGING IN REAR OF AIRCRAFT. THE NR 1 ENGINE WAS BROUGHT TO IDLE AND THE STALLING CEASED. THE AIRCRAFT WAS DIVERTED TO RDU WHERE IT LANDED WITHOUT INCIDENT. A BOROSCOPE OF THE NR 1 ENGINE FOUND THE 6TH AND 7TH STAGE COMPRESSOR DAMAGED. THE NR 1 ENGINE WAS REMOVED AND REPLACED. A POWER ASSURANCE/TRIM RUN WAS PERFORMED IAW MM 71-00-00 AND ALL PARAMETERS WERE NORMAL. INVESTIGATION REVEALED AN 8TH STAGE STATOR SUPPORT SHELF HAD BROKEN OUT AND WAS THE PRIMARY CAUSE OF ENGINE FAILURE. (M)