What was found
(CAN) SMOKE IN CABIN DURING, 2 TO 3 LOUD NOISES WERE HEARD ACCOMPANIED BY ACFT YAW. THE CREW OBSERVED SIGNIFICANT TORQUE FLUCTUATIONS ON NR 2 ENGINE AND THEY RETARDED THE POWER LEVER A. F/A REPORTED SMOKE IN THE CABIN AND THE ENGINE WAS SHUTDOWN. THE ACFT RETURNED TO POINT OF ORIGIN WHERE AN UNEVENTFUL SINGLE ENGINE LANDING WAS ACCOMPLISHED. POST-FLIGHT INSPECTION REVEALED THE TURBOMACHINE CHIP DETECTOR HEAVILY CONTAMINATED. THE ENGINE IS BEING REMOVED AND SENT FOR INVESTIGATION AND REPAIR.