What was found
7400-STL-LEFT PROPELLER FEATHERED IN FLIGHT, POWER MANAGEMENT KNOB IN CLIMB, TORQUE WAS 85 PERCENT. NP WENT TO 20 PERCENT, ENGINE TORQUE WENT FULL SCALE, CREW RETARDED POWER, PROPELLER UNFEATHERED, AIRCRAFT RETURNED WITHOUT INCIDENT. MAINTENANCE INSPECTED LEFT ENGINE, PERFORMED DOWNLOAD OF FDAU FOR EXCEEDANCE DATA, NO EXCEEDENCES WERE COLLECTED, MAINTENANCE REPLACED THE RIGHT ENGINE TORQUE SIGNAL CONDITIONER (CROSS TALK BETWEEN LEFT AND RIGHT ENGINES SIGNAL CONDITIONERS CAUSING AUTOFEATHER), PERFORMED GROUND RUN, AIRCRAFT WAS RELEASED FOR SERVICE.