As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ON FINAL APPROACH TO A CONFINED AREA, PILOT HEARD LOW ROTOR WARNING HORN FOLLOWED BY DROOP IN MAIN ROTOR SPEED. EMERGENCY AUTO ROTATION WAS EXECUTED INTO THE LANDING AREA. UPON TOUCHING THE GROUND ELT WAS SET OFF. INITIAL MAINTENANCE INVESTIGATION INDICATED POSSIBLE HMU FAILURE AS THE CAUSE OF THE DECLARATION.