HISTORY OF FLIGHTOn August 6, 2012, about 1025 central daylight time, an Ayres Corporation S2R-T34, N365SM, descended and impacted terrain near Lakin, Kansas. The airline transport pilot was uninjured. The airplane sustained substantial damage to its fuselage and wings. The airplane was registered to and operated by Tri-Rotor Spray & Chemical under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Day visual flight rules (VFR) conditions prevailed for the flight, which did not operate on a VFR flight plan. The local flight originated from the Lakin Airport (36K), near Lakin, Kansas, about 1020. The pilot's accident report indicated that he had encountered ground level turbulence for the past hour during his previous flights and that he had planned to discontinue any more application flights at the end of this load. He calculated the airplane's weight to be 9,000 lbs. The pilot said that he performed a downwind turn proceeding southbound into the wind. There was a transmission line on the north side of the east/west road and a normal power line on the south side of the same road. He stated that the turn was normal, there was turbulence, and he was flying the airplane within a couple feet of the global positioning system swath guidance. The pilot then flew the airplane in a descent into the field beyond the power lines and leveled out approximately three to five feet above the corn. He reported that he then experienced some "sink" and applied back stick pressure to maintain "level." The airplane descended enough for the wheels to touch the tops of the corn. The airplane subsequently pitched nose down as well as slowed down, which led to further penetration into the corn, and ultimately resulted in the airplane's rapid deceleration and complete stop. The pilot said that the propeller was stopped and the engine was running. He reduced the power to idle and shut down the engine. PERSONNEL INFORMATIONThe 59-year old pilot, who occupied the center seat, held a Federal Aviation Administration (FAA) airline transport pilot certificate with commercial pilot privileges for single-engine land airplanes. The pilot reported that his most recent FAA second-class medical certificate was issued October 18, 2011, with limitations for corrective lenses, and his last flight review was completed on November 20, 2011. The pilot reported he had accumulated a total flight time of 3,208 hours, of which 1,834 hours were in the same make and model aircraft. AIRCRAFT INFORMATIONN365SM was a 1981 Ayres S2R-T34, tail-wheel equipped, single-engine, low-wing, all-metal airplane, used for aerial application of agricultural products, with serial number T34-053DC. The pilot reported that the airplane's last annual inspection was performed on May 2, 2012, when the airplane accumulated 8,368.5 hours of total time, and that the airplane subsequently accumulated about 139 hours of flight time following the inspection. A Pratt & Whitney Canada PT6A-34AG turboprop engine, with serial number PCE 56009, powered the airplane. That engine was overhauled, subsequently installed on the airplane on May 2, 2012, and it had accumulated a total time of 44,727.3 hours with zero time since overhaul. The engine drove a three-bladed constant speed, Hartzell HCB3TN-3D, propeller. METEOROLOGICAL INFORMATIONAt 0954, the recorded weather at the Garden City Regional Airport, near Garden City, Kansas, was: Wind 180 degrees at 14 knots gusting to 17 knots; visibility 10 statute miles; sky condition clear; temperature 27 degrees C; dew point 15 degrees C: altimeter 30.17 inches of mercury. The airport had an elevation of 2,891 feet and based on the weather at that time, had a calculated density altitude of 4,912.4 feet. AIRPORT INFORMATIONN365SM was a 1981 Ayres S2R-T34, tail-wheel equipped, single-engine, low-wing, all-metal airplane, used for aerial application of agricultural products, with serial number T34-053DC. The pilot reported that the airplane's last annual inspection was performed on May 2, 2012, when the airplane accumulated 8,368.5 hours of total time, and that the airplane subsequently accumulated about 139 hours of flight time following the inspection. A Pratt & Whitney Canada PT6A-34AG turboprop engine, with serial number PCE 56009, powered the airplane. That engine was overhauled, subsequently installed on the airplane on May 2, 2012, and it had accumulated a total time of 44,727.3 hours with zero time since overhaul. The engine drove a three-bladed constant speed, Hartzell HCB3TN-3D, propeller. WRECKAGE AND IMPACT INFORMATIONA FAA inspector examined and took pictures of the wreckage. The airplane came to rest upright near a cornfield. Examination of the airplane and review of the inspector's photographs revealed the four corners of the airplane were intact. The propeller remained attached to the engine, but one propeller blade tip was separated from its propeller blade. The separated blade tip exhibited chordwise scratches. One blade exhibited chordwise abrasions and another blade showed S-shaped bending. ADDITIONAL INFORMATIONThe pilot's safety recommendation indicated that he had caught a cold over the prior weekend and he should have stayed in bed. Additionally, he listed more rest, and commented that he had been relocating to a new house where he worked long hours there "till late." Another recommendation was to set personal minimums higher in reference to temperature, wind, and turbulence. He also indicated that there is no opportunity to obtain dual instructional experience in a work environment. TESTS AND RESEARCHThe recovery company removed the engine, crated it, and it was shipped to the engine manufacturer for detailed examination. The examination revealed that the engine sustained deformation of the exhaust duct consistent with impact damage and circumferential witness marks on the power turbine disc, power turbine shroud, and the power turbine guide vane ring consistent with adjacent component rotational contact. The first stage compressor shrouds showed rubbing marks from its rotor airfoil tips. No anomalies were observed during the testing of the fuel control unit, fuel pump, fuel nozzles, starting flow control, propeller governor, fuel heater, and compressor bleed valve, which would have prevented normal operation prior to the accident.