According to the flight instructor, the purpose of the flight was to conduct hovering and pattern work maneuvers. After the completion of the flight, the student pilot was hovering and awaiting clearance to return to the ramp. The flight instructor said she was looking around to ensure the runway was clear and making a radio call, when suddenly, the helicopter pitched up. She attempted to gain control of the helicopter but was unsuccessful. The helicopter collided with the ground and rolled over. The flight instructor said she was not on the flight controls prior to the accident event. According to the student pilot, he stated that he was practicing hovering maneuvers for about an hour. He said that he was tired and transferred the controls to the flight instructor, as they waited to cross the field. The student pilot said that while they were waiting, the nose pitched up and the tailboom hit the ground. The helicopter then collided with the ground and rolled over. He said that he was not on the flight controls at the time of the accident. The helicopter was inspected by a Federal Aviation Administration (FAA) inspector and revealed structural damage to the airframe. No flight control anomalies were discovered that would have precluded normal operation. During the FAA interviews of the pilots, both seemed to have believed that the other was on the flight controls at the time of the accident.