What was found
(CAN) NR 2 ENGINE HAD A TORQUE SURGE OF 107 PERCENT ON APPROACH. THE TORQUE SURGE SUBSIDED AFTER A FEW SECONDS. THEN A LOUD BANG WAS HEARD AND THERE WAS SMOKE IN THE COCKPIT AND CABIN. THE AIRCRAFT DECLARED AN EMERGENCY AND LANDED WITHOUT INCIDENT. POST-FLIGHT INSPECTION FOUND WHEN THE HP TURBINE WAS TURNED A WEIRD SOUND WAS HEARD. THE ENGINE WAS REPLACED. THE REMOVED ENGINE WAS SENT TO P&W FOR INVESTIGATION.