On June 14, 2010, about 0915 central daylight time, an Air Tractor Inc., AT-602, N4257R, was substantially damaged during a forced landing following a partial loss of engine power near Penrose, Arkansas. The commercial pilot, the sole occupant, sustained minor injuries. The airplane was registered to and operated by Reynolds Flying Service Inc., of McCrory, Arkansas. Visual meteorological conditions prevailed and a company flight plan was filed for the 14 Code of Federal Regulations Part 137 agricultural application flight. The local flight departed at an unknown time. According to the pilot, while approximately 75 feet above the ground, the turbine powered airplane experienced a partial loss of engine power. Unable to maintain altitude, the pilot performed a forced landing to a wet rice field. During landing, the airplane impacted a dirt mound, nosed over, and came to rest inverted. A Federal Aviation Administration (FAA) inspector responded to the accident site and reported that the airplane's empennage, left wing and fuselage, sustained structural damage during the accident. The FAA inspector, along with a representative from Pratt and Whitney Canada Inc., examined the engine. The compressor turbine and the first stage power turbine vane ring displayed contact signatures consistent with the engine being powered near idle at the time of impact. Functional testing of the fuel control unit revealed that the unit's evacuated bellows had developed a fatigue crack in the outer ply surface. This crack would have resulted in a reduced fuel flow to the engine, and a subsequent loss of engine power. Laboratory analysis concluded that the crack had originated in an area of several corrosion pits. The cause of the corrosion could not be conclusively determined.