What was found
FERRY FLIGHT UNDER CFR PART 91. APPROXIMATELY 15 MINUTES INTO FLIGHT. STRAIGHT AND LEVEL CRUISE AT 80 PERCENT TORQUE, PILOT HEARD THE TORQUE WARNING HORN AND IMMEDIATELY AFTER THE ENGINE SPOOLING UP, PILOT LOWERED THE COLLECTIVE AND NOTED THE TORQUE DECREASING BELOW THE RED LINE. PILOT SCANNED TO THE N2/NR TACHOMETER AND NOTED AN ENGINE/ROTOR INDICATION OF APPROXIMATELY 122 PERCENT. PILOT IMMEDIATELY BEGAN TO SMOOTH DECREASE THE THROTTLE AS HE TURNED TOWARD THE CLOSEST SUITABLE LANDING SITE. THE PILOT PERFORMED A AUTOROTATION WITH POWER ON.