On July 3, 2013, about 0605 mountain daylight time, a WSK PZL Mielec M-18B (turbine-powered Dromader), N7643J, was substantially damaged during takeoff at Hubler Field Airport, Caldwell, Idaho. The commercial pilot, the sole occupant on board, was not injured. Valley Air Service, Inc., was operating the airplane under the provisions of 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed for the local aerial application flight, which was originating at the time of the accident. A flight plan had not been filed. The pilot stated that this was his first flight for the day, and he had approximately 490 gallons of applicant and 120 gallons of fuel on board. He taxied to the end of runway 29, a 2,800-foot-long runway and applied power for takeoff. The pilot said the airplane appeared to accelerate normally until the tail wheel came up and then the airplane's acceleration did not seem normal. He adjusted the power lever forward a bit, but the torque did not seem to increase. As he reached the end of the runway, he realized that he would not make it off the ground and that it was too late to abort. The pilot advanced the power lever all the way forward but the torque indication was only in the 80's percentile range. He pulled back on the control stick, and the main wheels left the ground, but the tail wheel felt like it was again on the ground. The pilot jettisoned the applicant load, but the airplane struck a fence in a nose high attitude approximately 100 feet from the end of the runway. The airplane tumbled and came to rest in a river approximately 350 feet from the fence. The airplane's turbine engine separated from the airframe, and both wings exhibited aft accordion leading edge crushing. The pilot stated that "a more prompt recognition of the problem and an earlier decision to dump the load [of applicant] may possibly have prevented the aircraft from hitting the fence." The pilot reported that when he arrived at the airport at 0500 the wind was light and variable. At 0615 the reported wind at Caldwell Industrial Airport, Caldwell, located 3 nautical miles from the accident site was wind from 110 degrees at 8 knots. During the postaccident examination, the Garrett AiResearch TPE331 turboshaft engine was removed from the accident scene and shipped to Honeywell Aerospace, Phoenix, Arizona. On August 1, 2013, a manufacturer's representative and a Federal Aviation Administration (FAA) inspector witnessed the disassembly of the engine. Additionally, the fuel control unit (FCU), propeller governor and P2T2 sensor were sent to Woodward, Inc., Rockford, Illinois, for examination under the supervision of an FAA inspector. At the conclusion of the examinations, no mechanical malfunctions or failures were found that would have precluded normal operation.