On May 7, 1997, at 1112 central daylight time (cdt), an Air Tractor, AT-301, N23640, operated by a commercial pilot, sustained substantial damage when during maneuvering the airplane struck some high-tension power lines. The airplane subsequently impacted the terrain, 12 miles north of Huron, South Dakota. Visual meteorological conditions prevailed at the time of the accident. The aerial application flight was being conducted under 14 CFR Part 137. A flight plan was not on file. The pilot reported no injuries. The local flight originated at Huron, South Dakota, at 1045 cdt. In his written statement, the pilot said that he had completed his turn to enter the field he was spraying. He entered the field down wind over the trees. On entering the field the airplane struck power transmission cables. The airplane impacted on the ground and came to rest in a wheat field. The Federal Aviation Administration (FAA) inspector who examined the wreckage at the scene found the airplane resting in a wheat field on its left side, approximately 400 feet northeast of a support tower for some east-west running transmission lines. Several ground impact marks were observed across the wheat field, between the transmission lines and the main wreckage, beginning 100 feet north of the transmission lines and proceeding north- northeasterly to where the fuselage came to its final rest. The left side of the airplane's fuselage was crushed in. The engine was broken free of the mounts and separated from the airplane. Both wings were separated from the airplane at the roots. The right wing was found resting next to the fuselage. It was bent, twisted, and crushed inward. The left wing was broken into several pieces and found scattered between the first impact mark and the main wreckage. Both main gear were bent up and aft onto the fuselage. The left horizontal stabilizer was broken off at the root. The vertical stabilizer, rudder, right horizontal stabilizer and right elevator were undamaged. The propeller remained attached to the flange and exhibited torsional bending and chordwise scratching. Part of a transmission line was found wrapped around the propeller. Flight control continuity was confirmed. Examination of the engine, engine controls and other airplane systems revealed no anomalies.