On July 22, 2002, at 1040 central daylight time, an Air Tractor AT-401B, N60747, operated by Farmers Spraying Service Inc., was substantially damaged when it impacted terrain during an approach to a cornfield. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 137 aerial application flight was not operating on a flight plan. The airline transport pilot was uninjured. The local flight originated from the Pratt Industrial Airport (PTT), Pratt, Kansas, at 1028. The pilot stated in a written statement that he departed to spray a cornfield field located about 4.3 nautical miles northwest of PTT. Upon his arrival at the cornfield, he determined that the wind was from the northeast about 10 mph from smoke, which he placed over his pivot point. Cumulus clouds were forming with high humidity and a slightly gusty breeze. He observed power lines bordering the west and south sides of the corn field. He decided to spray the field in a north/south race track pattern. He set up for a shallow downline coming over the power lines on his second lap or fourth pass over the field with his airspeed increasing through 95 mph (30-32 inches of manifold pressure and 2,175 rpm). He began to roundout 5-10 feet above the corn, but the airplane continued its downline. He then added full power and pitched up slightly, but the airplane settled into the corn. Inspection of the accident site by the Federal Aviation Administration revealed the airplane contacted the corn crops about 309 feet north of the south power lines. The wreckage path consisted of the left spray boom located about 513 feet north of the power lines, a ground scar located about 792 feet north of the power lines, and the airplane which was 1,143 feet north of the power lines. The airplane was upright and facing towards the southwest. The airplane sustained damage to the rear fuselage, tail section and landing gear. The outboard sections of the propeller were curled backwards. Flight control and engine continuity was confirmed. The pilot stated that he had about 300 gallons of CAPTURE 2EC chemical and estimated that there were 232 gallons remaining at the time of the accident. He also reported the fuel tanks were about 2/3 full. The Great Bend, Kansas, Automated Weather Observing Station, located about 35 nautical miles north-northwest, recorded at 1055: wind 360 at 11 knots gusting to 15 knots; temperature 24 degrees Celsius (C); altimeter setting 30.05 inches of mercury. The station elevation is 1,887 feet. The density altitude was about 3,264 feet.