What was found
(CAN) SHORTLY AFTER ENTERING CRUISE FLIGHT THE PF NOTED A 5% TORQUE SPLIT. THE PF WAS ABLE TO SUCCESSFULLY MATCH THE TORQUES WITH THE COLLECTIVE TRIM SWITCH. A FEW MOMENTS LATER AFTER COMPLETING A CRUISE CHECK, THE PILOTS NOTED A LARGE TORQUE SPLIT IN EXCESS OF 40%. THE PNF ATTEMPTED TO MATCH THE TORQUES WITH THE TRIM SWITCH BUT WAS ONLY ABLE TO OBTAIN AN ADDITIONAL 4 - 6% RESIDUAL TORQUE. THE PNF REQUESTED THE PF UTILIZE THEIR TRIM SWITCH BUT NO ADDITIONAL CHANGE IN TORQUE WAS OBSERVED. OEI PARAMETERS WERE ESTABLISHED & BOTH PILOTS AGREED THAT THE NR 1 ENG WAS THE MALFUNCTIONING ENG. THE NR 1 ENG APPEARED TO REMAIN AT GND IDLE CONDITIONS WITH A MINIMAL AMOUNT OF RESIDUAL TORQUE AVAILABLE. AN EMER WAS DECLARED WITH ATC & A SINGLE ENG LONG FIELD APPROACH & LANDING WAS SUCCESSFULLY COMPLETED TO RNWY 25 AT AIRPORT. THE NR 1 ENG CONDITION REMAINED UNCHANGED AFTER LANDING & THE ENG WAS SHUT DOWN WITHOUT FURTHER INCIDENT.