On August 14, 2008, about 1400 Pacific daylight time, an experimental Kolb MK III airplane, N18EX, impacted the terrain about one-quarter mile south of the runway at Richland Airport, Richland, Washington. The student pilot, who was the sole occupant of the airplane, was killed in the accident. The airplane, which was owned and operated by the pilot, was being flown in visual meteorological conditions. The pilot reportedly intended to stay in the traffic pattern during the 14 CFR Part 91 personal flight. No flight plan had been filed. According to witnesses, about 20 minutes prior to the accident flight, the pilot had flown another small experimental or ultra-light airplane. During that flight, the pilot took off from runway 01, climbed to about 200 feet above ground level (agl), and then leveled off. Almost immediately after leveling off, and long before reaching the departure end of the runway, the pilot executed a 180-degree reversal turn that put him on a low-level downwind near the point where he soon turned onto a base leg. This sequence of maneuvers then ended with the pilot rolling out on a short final for a landing. According to the witnesses, this sequence produced a short tight low-level traffic pattern for the pilot. The pilot flew at this airport almost on a daily basis, and it was the opinion of the witnesses that he flew this type of pattern in order to reduce the time it took for him to get around the traffic pattern for another landing in the light slow airplane he normally flew. The witnesses also stated that they believed the pilot had owned the airplane for about 10 years, and that he flew it almost every day, usually early in the morning around 0700. They further stated that he usually flew "aggressively," but that they did not feel that he was normally "unsafe." During the accident flight, the pilot took off, climbed to about 200 feet agl, leveled off, appeared to make some small power adjustments, and then entered a "steep" right turn. Just as the airplane had passed through nearly 180 degrees of turn, its bank angle increased to almost 90 degrees, and the pilot appeared to add a substantial amount of power. According to witnesses, almost immediately thereafter, the airplane appeared to stall and descend steeply into the terrain. The engine, which is mounted in a pusher position, reportedly was running strong and smooth during the descent, and continued to run for at least 15 seconds after the impact. The airplane's fuel tank was at least three-quarters full. A post-accident inspection of the airplane's structure and flight controls by a Federal Aviation Administration Airworthiness Inspector did not reveal any anomaly or malfunction that would have contributed to an in-flight loss of control. The inspector also completed a partial teardown inspection of the engine, and determined that its ignition system was able to produce spark at the sparkplugs, that its fuel system was able to provide adequate fuel to the cylinders, and that the air inductions system was unobstructed. An autopsy performed by the Benton County Coroner determined that the manner of death was "accidental," and that the mechanism of death was, "Respiratory arrest secondary to central nervous system damage." A toxicology examination performed by the Washington State Toxicology Laboratory on samples taken from the pilot was negative for ethanol in the blood and vitreous fluid, and did not detect any CNS drugs. The carbon monoxide concentration was less than five percent saturation.