What was found
IN CRUISE FLIGHT, AIRCRAFT YAWED TO LEFT AND VIBRATION WAS FELT IN TAIL ROTOR PEDALS. AIRCRAFT WAS LANDED AT DESTINATION, AND PILOT DISCOVERED EXHAUST STACK FROM NR 1 ENGINE MISSING, AND DAMAGE TO BOTH TAIL ROTOR BLADES. MAINTENANCE FOUND THE NR 1 ENGINE OUTBOARD EXHAUST STACK CLAMP HAD FAILED AND THE EXHAUST STACK DEPARTED THE AIRCRAFT. THE TAIL ROTOR WAS STRUCK BY THE EXHAUST STACK AND BOTH TAIL ROTOR BLADES WERE DAMAGED. THE TAIL ROTOR ASSEMBLY, EXHAUST STACK AND CLAMP WERE REPLACED.