What was found
PILOT REPORTED VIBRATION, BURNING RUBBER ODOR AND LOSS OF ROTOR RPM WHILE IN CRUISE FLIGHT, DURING DOWNWIND PORTION OF TRAFFIC PATTERN PRACTICE. PILOT ENTERED AUTOROTATION AND PERFORMED SUCCESSFUL AUTOROTATION AND POWER OFF LANDING. UPON EXAMINATION OF ACFT ON SCENE, THE FAN SHAFT WAS OBSERVED TO BE BROKEN AND SEPARATED JUST FORWARD OF THE LOWER ACTUATOR BEARING. AFFECTED PARTS WERE REMOVED AND RETAINED BY THE FAA FOR EXAMINATION BY THE MFG.