As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT HEARD HUMMING NOISE AND LIGHT VIBRATION. CARRIED OUT AN EMERGENCY LANDING, 30 FEET OFF GROUND HEARD LOUD BANG AND LOST DIRECTIONAL CONTROL. AFTER INVESTIGATING, FOUND CLUTCH SHAFT FAILURE DUE TO SWITCH FAILURE ALLOWING BELT TENSION ACTUATOR TO OVER TENSION THE V-BELTS. ROBINSON ISSUED SB R44SB- 21