On May 8, 2005, about 1935 eastern daylight time, an unregistered, amateur built New Kolb Slingshot, was substantially damaged while departing the Lima Allen County Airport (AOH), Lima, Ohio. The non-certificated pilot/owner was seriously injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the local personal flight, conducted under 14 CFR Part 91. According to the pilot's verbal and written statements, he had departed runway 32 on his second flight of the day. He was on the upwind leg of the traffic pattern, climbing through an approximate altitude of 500 feet msl. when the engine started to overheat. The pilot reduced power rapidly and the engine "hesitated," but continued to run at partial power. He then attempted to restore power, however during the attempt, the airplane "mushed and stalled." A witness observed the airplane, flying at an altitude about 60 to 80 feet above ground level, when the airplane "seemed to fall" into a building materials storage area, and came to rest inverted. Upon arrival by the Ohio State Highway Patrol (OSHP), an initial examination of the accident site revealed that the airplane had impacted a stack of windows, a display case and then finally came to rest on a stack of vinyl siding. The fuel tank was observed by the officer to be leaking gasoline, and the engine was still running prior to being shut off by a pilot rated witness. During an interview conducted by the OSHP, the airport office manager stated that the airplane was an "ultralight" and was required to meet the airworthiness certification standards of 14 CFR 103. A post accident inspection conducted by Federal Aviation Administration (FAA) inspectors revealed, that the airplane weighed 420 pounds, and did not bear any registration markings. According to 14 CFR Part 103, which prescribes the rules governing the operation of ultralight vehicles in the United States, an ultralight vehicle is a vehicle that "weighs less than 254 pounds empty weight." It also states, "ultralight vehicles are not required to be registered or to bear markings of any type." An examination of the engine by an FAA inspector was inconclusive, and the source of the over temperature condition and subsequent partial loss of power could not be determined. The recorded weather at AOH, at 1953, was: winds from 120 degrees at 6 knots; visibility 10 statute miles; clear skies; temperature 71 degrees Fahrenheit; dew point 48 degrees Fahrenheit; altimeter setting 30.03 inches of mercury.