On September 30, 1997, at 1445 central daylight time, a Bell 47, N9005T, registered to Aerial Blades, Inc., of Flandreau, South Dakota, piloted by a commercial pilot, impacted the terrain, while positioning the aircraft for an aerial application mission. The helicopter was substantially damaged. The pilot reported serious injuries. The local 14 CFR Part 137 flight was operating in visual meteorological conditions. No flight plan was on file. The flight originated from a farm field in Pipestone, Minnesota, exact time unknown. The pilot stated, in an interview with the Federal Aviation Administration, that while he was ferrying the helicopter to the next field he, "heard a loud bang from behind." The pilot stated that the cyclic control, "jerked," helicopter began to vibrate, and rotor RPM decreased. The pilot stated that he increased the throttle, but the engine responded as if there was no load on the engine. The pilot initiated autorotation, but was unable to regain control, and the aircraft impacted the terrain. Post accident investigation revealed that one of two pitch control rod assemblies had fractured between the clevis and turnbuckle. The Material Laboratory Division of the National Transportation Safety Board, Washington D.C., examined the fractured control rod assembly. Examination of the fracture showed areas of fatigue striations and multiple crack initiation sites on the machined surface. For additional information, see attached Material Laboratory Factual Report.