On August 14, 2003, about 1705 central daylight time, an Air Tractor AT-301, N4339S, piloted by a commercial pilot, sustained substantial damage when it struck a powerline while maneuvering near Aplington, Iowa. The airplane subsequently impacted the ground. The 14 CFR Part 137 aerial application flight was operating in visual meteorological conditions without a flight plan. The pilot received serious injuries. The flight departed Ackley Municipal Airport (4C7), Ackley, Iowa, at 1630. According to the pilot's written statement, he departed 4C7 with fuel and 260 gallons of chemical mix. The pilot reported that the airplane impacted power lines while maneuvering for a headland application pass, subsequent to completing a chemical application to a soybean field. The pilot stated that the airplane's impact with the power lines resulted in a loss of pitch control. The pilot reported the airplane "impacted the ground in a very nose-down attitude completely destroying the aircraft."