While approaching to land during an agricultural operation, the helicopter suddenly and uncontrollably yawed to the right. The pilot was able to make a successful forced landing although the helicopter was substantially damaged.
Engineering investigation found that one of the tail rotor driveshaft segments had failed. The aft yoke, which is normally bonded to the driveshaft tube, had separated at the bond line, rotating freely on the tube, resulting in loss of drive to the tail rotor. Despite extensive testing, no reason for the failure could be determined due to the damage sustained during the failure. BHT has advised that the new driveshafts have a riveted joint at the yoke in addition to the bonding, and they are pursuing a service bulletin to address the older driveshafts already in service.