On August 20, 2003, 0815 central daylight time, a Cessna T188C, single-engine agricultural airplane, N3872J, was substantially damaged during a forced landing following a loss of engine power while maneuvering near Colorado City, Texas. The airplane was owned and operated by S&V Aerial Inc., of San Angelo, Texas. The commercial pilot, sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 137 aerial application flight. The local flight originated from Colorado City Airport, near Colorado City, Texas, approximately 0800. The 2,910-hour pilot reported in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) that while maneuvering to return to a field he was performing aerial application on, the engine lost power. As the pilot terminated his aerial application run and looked for a suitable place to land, he turned on the fuel boost pump, advanced the throttle to full power, and set the mixture to rich. Subsequently, he saw three sets of power lines directly in front of his position and pitched up to avoid hitting them. As he crossed over of the third set of power lines, "the airplane stalled" and impacted terrain in a "left wing and nose low" attitude. The airplane came to rest upright within a cotton field. Examination of the airplane by an Federal Aviation Administration (FAA) inspector revealed that both main landing gears were separated, the left rear wing spar was damaged, and the left side of the empennage was buckled aft of the cabin. Further examination revealed both fuel tanks were "almost" full of fuel. Review of the aircraft maintenance records revealed the engine was last overhauled on April 2, 1998. The number five cylinder was replaced on October 31, 2001. The number four, five, and six cylinders, pistons, and rings were replaced on October 10, 2002. The most recent annual inspection was performed on May 6, 2003. The Continental TSIO-520-T(1) engine, serial number 515431, was examined by a representative of Teledyne Continental Motors on September 10, 2003, under the supervision of the FAA inspector, at a maintenance facility near Seminole, Texas. Examination of the engine revealed that the crankshaft, part number 649130DU, serial number K209195N, was fractured at the cheek for the number two cylinder. On November 24, 2004, at the facilities of Teledyne Continental Motors, near Mobile, Alabama, a metallurgical examination was performed on the crankshaft under the supervision of an FAA inspector. The examination revealed that a fracture initiated from at least two distinct origins in the fillet between the number 3 cheek and number 2 main journal, witch beach marks throughout. The edge of the fractured surface was smeared. The reason for the failure of the crankshaft was undetermined.