On September 28, 2015, about 1925 central daylight time, an experimental, amateur-built Rans S18 airplane, sustained substantial damage when it impacted a field 2 miles east of Shattuck, Oklahoma. The pilot, the sole occupant, received fatal injuries. The unregistered airplane was owned and operated by the non-certificated pilot. Visual meteorological conditions prevailed at the time of the accident and no flight plan was filed. The flight departed about 1923 from a grass airstrip located approximately .5 miles east of the accident site, and was en route to Gage Airport (GAG), Gage, Oklahoma, located 5 miles northeast of the accident site. The pilot of the accident airplane had flown to the grass airstrip along with two ultra-light trike aircraft. One of the trike pilots reported that each aircraft did two or three landings at the grass airstrip. On the final takeoff from the airstrip, the two trike pilots were taxiing their aircraft to the northeast end of the airstrip to prepare to depart. The accident airplane was faster than the trikes and departed while they were still taxiing so they did not see the accident airplane again. The trike pilot stated that he believed that the accident airplane might have departed to the west initially. The two trike aircraft departed to the southeast once airborne. The trike pilot stated that perhaps the accident pilot was making a turn to join the two trike aircraft when the accident occurred. No one witnessed the accident. Another witness reported that he drove by the grass airstrip about 1920 and saw three aircraft on the ground at the airstrip. When he drove by the airstrip about 1925, he saw the wreckage of the accident airplane in the field. The on-site examination of the wreckage revealed that the impact heading was to the southeast. The leading edges of the wings exhibited aft crushing and buckling. The nose of the fuselage exhibited aft and upward crushing. The tail boom was buckled about mid-span. The empennage exhibited minimal damage. The flight controls exhibited continuity from the cockpit controls to the control surfaces. The visual examination of the engine and gearbox revealed no preimpact anomalies. The three-bladed composite propeller remained attached to the engine gearbox. One blade was broken off about 12 inches from the propeller hub. Another blade was shattered about mid-span to the end of the blade. The chambered side of the third blade was delaminated and separated from the rest of the blade. The accident pilot was not certificated. A witness reported that the accident pilot started flying about two years before the accident. He stated that the accident pilot purchased the non-certificated airplane in a trade and flew it about 2-3 times a month – typically in the morning or late evening. He stated that the airplane was a good running airplane and that the engine ran like a "champ". No pilot logbook or aircraft maintenance records were obtained during the investigation. The autopsy of the pilot was performed at the Office of the Chief Medical Examiner, Oklahoma City, Oklahoma, on September 29, 2015. The cause of death was "multiple trauma due to a motor vehicle accident – ultra light pilot." A Forensic Toxicology Fatal Accident Report was prepared by the FAA Civil Aerospace Medical Institute. Atenolol was detected in the urine and blood. No carbon monoxide was detected in the blood. The test for cyanide was not performed. 22 (mg/dL, mg/hg) ethanol was detected in the blood and 20 (mg/dL, mg/hg) ethanol was detected in the urine. Atenolol is a beta blocker used to treat hypertension and abnormally fast heart rhythms. At 1853, the surface weather observation at GAG was: wind 140 degrees at 4 kts; 10 miles visibility; sky clear; temperature 28 degrees C; dew point 12 degrees C; altimeter 29.90 inches of mercury.