On July 21 2004, at approximately 1130 mountain daylight time, a Davis-Zenair, STOL CH 801, N10627, was substantially damaged following a loss of engine power, when it impacted terrain during a forced landing on a field near Erie, Colorado. The airline transport certificated pilot was not injured. Visual meteorological conditions prevailed at the time of the accident. The local test flight was being conducted under the provisions of Title 14 CFR Part 91 without a flight plan. The flight originated at Erie-Tri-County Airport (48V), Erie, Colorado, at approximately 1000. According to the pilot, the airplane's 1988 liquid-cooled Mazda Twin-rotor automotive engine had accumulated approximately 2,500 road miles, but the airplane had accumulated a total of only 1.5 hours of flight time. The pilot said he was conducting the initial test flight and had completed 10 takeoffs and landings on runway 33. While on crosswind following the 11th takeoff, he noticed that the indicated engine coolant temperature had increased from, a normal operating temperature of 110 degrees F., to 220 degrees F. The increase in temperature was followed by a drop in engine rpm and a partial loss of engine power. Unable to maintain pattern altitude, the pilot attempted to land on runway 09, but the pilot was forced to land in a plowed field approximately 200 feet short of the runway. The impact displaced the left wing aft, collapsed the nose landing gear assembly, and buckled the firewall. An examination of the airplane revealed no anomalies.