Maintenance was performed on the aircraft’s fuel system and flight test was required. The pilot made a normal takeoff with a right hand traffic pattern. A normal approach was performed with a go-around. A second right pattern to runway 18 was performed. The pilot performed a straight-in auto-rotation for a rotor RPM check. He stated that he flared at 25 feet above the ground, leveled at 5 feet with the “(power off),” and then performed a hovering auto-rotation where both skids contacted the ground with zero forward airspeed and a heading was maintained. The pilot noticed the engine RPM began to rapidly increase and he rolled the throttle completely off and lowered collective. He reported that the left skid was coming off the ground and he applied full left cyclic and full down collective. The aircraft teetered with the left skid approximately four to six inches above ground and the aircraft continued to roll right. The pilot stated, “I believe the maneuver was performed successfully and either a strong wind gust or mechanical defect caused the roll over.” The pilot subsequently stated that the helicopter had an articulated landing gear system. He said that the struts travel approximately seven to eight inches and “if only one side retracts it causes a ‘rolling moment’.” About 22 minutes before the accident, the recorded winds about seven nautical miles and 155 degrees from the accident site were 200 degrees at 14 knots with gusts to 32 knots. An examination of the accident helicopter’s controls and landing gear revealed no anomalies.