HISTORY OF FLIGHT On August 20, 2011, about 1139 mountain daylight time, a Piper PA-25-235 airplane, N7051Z, was substantially damaged when it impacted terrain after conducting aerial application work about 5 miles north-northeast of Whitewood, South Dakota. The pilot was fatally injured. The airplane was registered to and operated by a private individual. The agricultural application flight was being conducted under the provisions of 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The local flight originated from Sturgis Municipal Airport (49B) about 1030, and was intending to return to Belle Fourche Municipal Airport (EFC) after the flight. The airplane owner stated that the pilot was applying insecticide to an alfalfa field about 12 miles north of 49B. The airplane was fueled the night prior to the accident. The pilot relocated the airplane from EFC to 49B. He subsequently completed three application flights without incident prior to the accident flight. The initial flight was flown with about 100 gallons of the water/chemical mixture and a full fuel load of 65 gallons. The final flight was to complete the application work on the field. The owner noted that the airplane was loaded with about 30 gallons of water/chemical mixture for the field, and about 30 gallons of fuel remained onboard. According to the owner, the pilot was planning return to EFC after completing the application work. A witness located about two miles south of the alfalfa field reported that she observed the accident airplane conducting the application work. Everything appeared to be normal and she noted that she could hear the airplane engine. About 1100, she observed the airplane depart the area toward the east, in the general direction of the hill where it crashed. The airplane impacted a hillside along the east side of a valley. The land owner located the wreckage about 1139. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with single-engine land airplane, instrument airplane, and helicopter ratings. The helicopter rating was limited to private pilot privileges. He was issued a second class airman medical certificate on January 13, 2011, with a limitation for corrective lenses. On that application, he reported a total flight time of 4,831 hours, with 78 hours flown within the previous 6 months. The pilot's logbook obtained by the FAA included an endorsement for a flight review dated August 1, 2009. The next previous entry was for a flight review dated May 3, 2003. The logbook included a flight time total of 4,153 hours subsequent to a flight review entry dated June 1, 1998. AIRCRAFT INFORMATION The accident airplane was a 1964 Piper PA-25-235 Pawnee, serial number 25-2819. It was a single-engine, tailwheel equipped airplane, currently certificated in the restricted-agriculture/pest control category. The airplane was initially issued an airworthiness certificate on April 29, 1964. The airframe had accumulated approximately 7,503 total flight hours at the time of the accident. The accident airplane was powered by a 235-horsepower Lycoming O-540-B2B5 engine, serial number L-8497-40. The engine had accumulated approximately 6,908 hours total time, with about 1,454 hours since overhaul. The most recent annual inspection was completed on June 1, 2011, at 7,382 hours total airframe time. The logbooks did not contain any entries subsequent to the annual inspection endorsement. METEOROLOGICAL INFORMATION Weather conditions recorded by the Black Hills Airport Automated Weather Observing System (AWOS), located approximately 10 miles west-southwest of the accident site, at 1135, were: wind calm, 10 miles visibility, clear sky, temperature 21 degrees Celsius, dew point 9 degrees Celsius, altimeter 30.15 inches of mercury. WRECKAGE AND IMPACT INFORMATION The airplane impacted a hill along the east side of a valley. The impact point was located about 14 feet below the crest of the hill, which led up to a plateau extending to the east. The airplane came to rest about 250 feet from the initial impact point. The impact path and airplane were both oriented on a northeast bearing. The airplane came to rest on its right side. Both wings were deformed and partially separated from the fuselage. The empennage remained attached to the fuselage; however, the right horizontal stabilizer was crushed consistent with ground impact. The flight control surfaces remained attached to the airframe. The engine and propeller remained attached to the airframe. One propeller blade was twisted and a portion of the blade tip was separated. The second propeller blade was curled aft over approximately the outboard one-half of the blade span. A portion of the blade tip was separated. A section of propeller blade was recovered about 100 yards north of the main wreckage. The landing gear had separated from the airframe and was located approximately 115 feet from the main wreckage. A postaccident examination of the airplane, including the flight controls and engine assembly, did not reveal any anomalies consistent with a preimpact failure or malfunction. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy of the pilot was performed on August 22, 2011 at the Rapid City Regional Hospital. The pilot's death was attributed to traumatic injuries sustained in the accident. The FAA Civil Aerospace Medical Institute toxicology report noted the following findings: 12 (%) Carbon Monoxide detected in Blood; No Cyanide detected in Blood; No Ethanol detected in Vitreous; Atorvastatin detected in Liver; Atorvastatin NOT detected in Blood. Atorvasatin is a prescription medication commonly used to treat lipid disorders and elevated cholesterol. ADDITIONAL INFORMATION A handheld global positioning system (GPS) receiver was recovered from the accident airplane. The data indicated that the airplane was operated on a total of 5 flights on the day of the accident. The initial flight departed EFC approximately 0703, arriving at 49B about 0725. This was followed by what appeared to be 4 application flights. The first and second application flights departed 49B about 0738 and 0835, respectively. The corresponding duration of these flights was about 37 and 39 minutes. In each case, the GPS track data indicated that the airplane proceeded northwest approximately 11 miles and made multiple passes within a local area before returning to 49B. The accident site was located at the south end of that local area. The third application flight departed 49B about 0949 and proceeded northwest to the same location as on the previous two flights. The GPS data indicated that a total of 8 combined north-south application passes were made during that flight. The aerial application area began approximately 0.5 mile north of the accident site and was about 0.6 miles in length. The data indicated that on four of the southbound passes, the pilot reversed course by turning east before executing a 180-degree turn back to the application area. On three of the southbound passes, the the pilot reversed course by extending south of the application area and executing a 180-degree turn. On one of those occasions, the pilot nearly overflew the accident site. The accident flight departed 49B about 1037 and proceeded northwest to the same location as recorded on the previous flights. However, the data ended at 1046:57 (hhmm:ss) shortly after the flight turned from a northwest course (approximately 305 degrees magnetic) to a northerly course (about 010 degrees magnetic) toward the application area. The final GPS data point was located about 0.3 miles south-southwest of the accident site. No further data was available.