What was found
(CAN) DURING A TRAINING FLIGHT, THE CREW WAS CONDUCTING A SIMULATED ILS APPROACH AT THE AIRPORT. DURING THE INTERMEDIATE APPROACH, 5 NM FINAL. THE NR 2 ENGINE BEGAN TO SURGE WITH FLUCTUATING TORQUE AND COMPRESSOR SPEEDS. A PRECAUTIONARY SHUTDOWN WAS COMPLETED AND THE ACFT RETURNED TO ITS ORIGIN AND MADE AN UNEVENTFUL SINGLE LANDING. THE MAINTENANCE CREW PERFORMED TROUBLESHOOTING AND HIGH POWER GROUND RUNS FOLLOWED BY 2 HRS FLIGHT TEST WITHOUT BEING ABLE TO DUPLICATE THE PROBLEM. THE ACFT HAS BEEN RETURNED INTO SERVICE.