On June 21, 2008, approximately 0800 central daylight time, a Mercer Avid Flyer Mk IV, N6880L, piloted by a commercial pilot, was substantially damaged when it collided with terrain following a loss of power during a forced landing approach at Augusta Municipal Airport (3AU), Augusta, Kansas. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 CFR Part 91 without a flight plan. The pilot, the sole occupant on board, was not injured. The local flight originated at Augusta approximately 0730. The pilot told an FAA inspector that the engine started overheating and he turned around and was returning to the airport. On approach at approximately 500 feet, the engine seized. The pilot attempted to make a forced landing in a field but the airplane landed hard on the terrain, bending the landing gear. It then slid 80 feet and struck a fence. Damage consisted of a wrinkled fuselage. The pilot reported the reason the engine seized was due to a failed thermostat, causing the engine to overheat.