Helicopter Tail Rotor Blade Separates in Flight, Results in Hard Landing and Rollover (N5374V)

Narrative

The pilot reported cruising at 500 feet above ground level over an open field when a loud bang was heard. The helicopter began to vibrate severely and spiral to the right. The pilot lost ground reference in the pre-dawn darkness after turning on the lights. Not wanting to land too hard, the pilot elected to leave the engine running and did not autorotate. The aircraft landed hard and rolled over after the landing skid failed.

Investigation

Investigation indicated that one tail rotor blade had separated at the tension torsion strap attach bolt hole. This is the transition area where the blade root casting and sheet metal blade skin are joined. The fracture surface of the casting appeared to be overloaded with no apparent indication of fatigue. The outboard blade section showed no indication of foreign object contact. All components of the helicopter were located in the impact area except one tail rotor blade.