On June 24, 2006, about 0800 central daylight time, an amateur-built experimental Miller Zenair Cricket MC-12 airplane, N36CZ, piloted by a private pilot, was substantially damaged during an in-flight collision with terrain near Lee's Summit Municipal Airport (LXT), Lee's Summit, Missouri. The personal flight was being conducted under 14 CFR Part 91 without a flight plan. Visual meteorological conditions prevailed at the time of the accident. The pilot sustained fatal injuries. The local flight departed from LXT about 0745. Witnesses reported that the pilot departed runway 18 (4,015 feet by 75 feet, concrete) and remained in the traffic pattern. As the pilot completed the first circuit around the traffic pattern, witnesses stated that he executed a low approach over runway 18 about 200 feet above ground level. The witnesses reported that during the low approach, the engines did not sound normal and described them as "out of synch" and "missing." One witness stated, "it sounded like one engine was spitting and coughing. . . . [The pilot] turned a left crosswind just south of runway 11/29 and shortly after, it sounded like the engine quit. One engine was still running though." The witnesses stated that the airplane turned to a left crosswind and subsequently left downwind. They noted that the airplane appeared to be descending as it was established on downwind. One witness stated that as it reached a point abeam the airport terminal building on downwind, the airplane "pitched up and snapped hard to the right and then went into a downward spiral." Another witness stated that "as the plane got lower, it was just above the tree line but still in sight. Suddenly the aircraft rolled over and headed straight for the ground." A post accident inspection revealed no anomalies consistent with a pre-impact failure. Aircraft debris was contained within the immediate area of the accident site. The flight control system exhibited damaged consistent with terrain impact. The right wing flight control surfaces had separated from the airframe and were located at the accident site. The nose of the airplane was crushed aft and both wing leading edges exhibited crushing. The engines had separated from the airframe and came to rest near the main wreckage. Both engines rotated and exhibited cylinder compression. The spark plugs were removed and their appearance was consistent with normal operation. The auxiliary fuel tank was separated from the airframe and intact. The tank was dry at the time of the post accident inspection. The main fuel tank was compromised. A trace of a fluid consistent in appearance and odor to 100-low lead aviation fuel was recovered from a fuel line. First responders to the accident site did not notice a large or distinct fuel odor at the accident site. A search of airport fueling records found no record of the accident pilot having purchased fuel at LXT from January 1, 2006, through the day of the accident. The aircraft logbook contained an endorsement for a condition inspection dated May 13, 2006, and was signed by the pilot. The aircraft total flight was 47.6 hours at the time of that inspection. The prior inspection was conducted on May 13, 2005, at 45.6 hours total time. The pilot held a private pilot certificate with a single-engine land airplane rating issued in April 1979. He held a third class airman medical certificate dated August 30, 2004. He reported a total flight time of 1,580 hours on his application for that medical certificate.