THE PILOT'S FAILURE TO CROSS-CHECK A FAULTY ENGINE SPEED INDICATION WITH OTHER ENGINE PERFORMANCE INDICATIONS TO VERIFY WHETHER AN ENGINE MALFUNCTION HAD ACTUALLY OCCURRED, AND HIS FAILURE TO MAINTAIN ADEQUATE ROTOR RPM DURING AN EMERGENCY LANDING. THE PILOT'S REACTION TO THE PERCEIVED ENGINE MALFUNCTION LED TO AN UNNECESSARY REDUCTION OF ENGINE POWER AND SUBSEQUENT EMERGENCY LANDING.