On August 3, 1996, at 1936 central daylight time, a Bell 206B III, N5015T, registered to and operated by Chem Air, Inc., collided with an unmarked power line near Barton, Alabama. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 137 aerial application flight. The helicopter was destroyed and the airline-transport rated pilot, the sole occupant, was fatally injured. The time of departure has not been determined. According to the operator of the helicopter, the purpose of the flight was defoliation of vegetation near the power lines. The loader of the chemical indicated that when the flight was due to return to refuel, he observed smoke near where the helicopter was spraying. He then called 911 and reported the crash. Examination of the crash site by an FAA inspector revealed a downed .990 inch diameter unmarked 161 KV transmission line that had been located about 97 feet above ground level. The helicopter was observed on its right side nearly inverted about 200 feet from the nearest power line tower and the downed cable was observed on the wreckage. Fire damage to grass was noted near where the downed cable contacted the ground. The tailboom which was attached to the airframe was displaced downward about 90-degrees from normal orientation and evidence of main rotor blade contact with the cockpit was noted. The helicopter was equipped with a GPS to be used to delineate spray locations. Examination of the airframe by a representative of the manufacturer revealed no evidence or preimpact failure or malfunction of the flight controls. The main rotor hub and blade assembly was separated at the mast. Examination of the fracture surface revealed evidence of overload failure. Examination of 1 of the main rotor blades revealed evidence of striations on the leading edge of the blade inboard of midspan. Both blades were damaged and evidence of electrical arching was noted on the trailing edge portion of 1 of the blade grips. A report is an attachment to this report. Examination of the engine by a representative of the manufacturer revealed no evidence of preimpact failure or malfunction. A report is an attachment to this report. A postmortem examination was performed by Steven T. Hayne, M.D., F.C.A.P., the Rankin County Designated Pathologist. The cause of death was listed as helicopter crash. Toxicological analysis of specimens of the pilot was performed by the FAA Accident and Research Laboratory. The results were negative for carbonmonoxide, cyanide, tested drugs, and ethanol. On the day and location of the accident the sunset was calculated to occur at 1954 hours. There were no known witnesses to the accident.