As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE NUT THAT HOLDS THE C908-1 YOKE ON TO THE INPUT DRIVE FOR THE MAIN GEARBOX WAS FOUND TO LOSE TORQUE IN TWO INCIDENTS CAUSING THE YOKE TO VIBRATE AND MAKE CONTACT WITH THE MAIN ROTOR TACH PICK UPS, AND CAUSE WEAR ON THE NUT AND SHAFT THREADS. THE COTTER PIN IN THE NUT WAS STILL IN PLACE. THE MAIN TRANSMISSION HAS BEEN SENT OUT TO ROBINSON HELICOPTERS LTD. FOR EVALUATION. (TC# 20090630006)