What was found
WHILE IN CRUISE FLIGHT, THE PILOT NOTICED A DECREASE IN MAIN ROTOR RPM AND THE NOSE OF THE HELICOPTER NOTICEABLY YAWED. THE PILOT DECREASED COLLECTIVE PITCH, BUT THE ENGINE POWER AND ROTOR RPM CONTINUED TO DECREASE. THE ENGINE DID NOT FAIL COMPLETELY. DURING THE TOUCH DOWN, THE HELICOPTER HIT THE GROUND HARD AND CUT OFF THE TAIL BOOM BY THE MAIN ROTORS. THE N1 FUEL CONTROL WAS REMOVED AS A SUSPECTED CONTRIBUTING FACTOR.