On August 9, 2015, about 1855 central daylight time, an amateur-built RAF 2000 GT rotorcraft gyroplane, N315LK, was substantially damaged after impacting a tree near Humboldt, Iowa. The pilot was fatally injured and the passenger was seriously injured. The gyroplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Day visual meteorological conditions prevailed for the flight, with no flight plan filed. The local flight departed from Humboldt Municipal Airport (0K7), Humboldt, Iowa about 1825. The passenger, who had flown with the pilot several times, stated the purpose of the flight was to take some pictures of his house and to "just fly around". After flying for about 30 minutes, the pilot made a low pass over the passenger's house on a southwesterly heading. The passenger heard the pilot state an exclamation, followed by a descent of the gyroplane. The passenger said the pilot "struggled" with the controls as the gyroplane descended below the tallest trees on his property. As the gyroplane approached the ground, the pilot increased engine power. The gyroplane made a right turn and impacted a lone pine tree which they had just flown by. The passenger's neighbor observed the gyroplane as it approached the accident site on a southwesterly heading. He heard a reduction in engine noise, followed by the gyroplane's descent below the taller trees on the passenger's property. He subsequently heard a rapid increase in engine noise, followed by a loud impact noise. PERSONNEL INFORMATION The pilot, age 58, held a sport pilot certificate with a rotorcraft gyroplane rating and a repairman experimental aircraft builder certificate. A review of the pilot's logbook revealed that he had accumulated 150.5 hours of flight time in gyroplanes, with over 14 hours flown in the accident gyroplane during the previous 90 days. The pilot never had a Federal Aviation Administration (FAA) Medical Certification examination. AIRCRAFT INFORMATION The 2012 amateur-built RAF 2000 GT gyroplane was equipped with a single pusher engine, teetering blade rotor system, and was configured for two occupants. The gyroplane was powered by a four cylinder Subaru EJ 2.2 engine, which was driving a three-bladed Warpdrive composite propeller. The gyroplane was last inspected on July 9, 2015 by the pilot, who conducted a 25-hour inspection. METEOROLOGICAL INFORMATION At 1915, the weather observation station at Fort Dodge Regional Airport (FOD), Fort Dodge, Iowa, located about 12 miles south of the accident site, reported the following conditions: wind 120 degrees at 3 knots, 10 miles visibility, clear skies, temperature 25 degrees C, dew point 20 degrees C, altimeter setting 29.92 inches of mercury. WRECKAGE AND IMPACT INFORMATION FAA personnel responded to the accident site and located the wreckage next to a lone pine tree in the passenger's front yard, at an elevation of 1,134 feet msl. The gyroplane came to rest laying on its side, with its nose pointed to the northeast. Fuel was leaking from several locations. There was no evidence of a post crash fire. The leading edge of the rotor blade did not have any noticeable impact marks. The 3-bladed composite propeller was broken off at the root of each blade, with segments located as far as 200 feet from the main wreckage. FAA personnel performed a subsequent examination of the gyroplane at the recovery location. Flight control continuity was established to all flight controls, with the exception of two cyclic control components, which had fractures consistent with impact damage. Engine crankshaft continuity was established via rotation of the propeller hub. Examination of the gyroplane revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. TESTS AND RESEARCH Fragments of the three composite propeller blades were shipped to the NTSB Materials Laboratory for examination. All three blades exhibited one or more fractured fragments near the root end, followed by long spanwise pieces. The outboard end of each long piece exhibited damage to the leading edge of the blade consistent with impact damage. The corresponding blade tips for all three blades were identified. Examination of the blades did not reveal any apparent anomalies or deficiencies with their composite structure. A video recorder was recovered from the accident site and evaluated by the NTSB Recorder Laboratory. No information relevant to the investigation was located on the recorder. MEDICAL AND PATHOLOGICAL INFORMATION On August 11, 2015, an autopsy was performed on the pilot by the Iowa Department of Public Health Examiner. The cause of death was due to blunt force injuries. The FAA's Civil Aeromedical Institute in Oklahoma City, Oklahoma performed toxicology tests on the pilot. Atenolol, yohimbine, and etomidate were identified in blood. Atenolol is used to treat high blood pressure. Yohimbine is used for the treatment of male sexual dysfunction. Etomidate is an anesthesia induction agent used in emergency treatment. A review of Humboldt County Memorial Hospital records revealed that etomidate was utilized during lifesaving efforts.