The pilot stated he was on a training flight, circling clockwise around a point, about 40 feet above ground level. He was approximately 400 feet from the point while at an indicated air speed of 35 knots. The aircraft suddenly started to increase its yaw rate to the right. He applied left pedal to stabilize the yaw rate, which continued to increase. He attempted to stop the high yaw rate with the appropriate pedal inputs, full left pedal; however the aircraft continued yawing. The helicopter completed two rapid 360 degree rotations. He realized he was not able to correct the high yaw rate with pedal inputs and entered into a hovering autorotation, which stopped the yawing. He landed the helicopter without injuries or damage to any property, however the aircraft sustained damage to the landing gear due to the hard landing. The pilot notified NTSB of the accident on March 23, 2007. The helicopter was shipped to the Robinson Helicopter Company facility for a hidden damage inspection and on June 13, 2007, NTSB was informed the helicopter did incur substantial damage. A completed Pilot/Operator Aircraft Accident/Incident Report was not received for this accident.