On August 1, 1999, at 1957 central daylight time, a Cessna 150L airplane, N444UF, was substantially damaged following a loss of control while maneuvering in the traffic pattern at the Coulter Field Airport, near Bryan, Texas. The flight instructor sustained minor injuries and the student pilot was not injured. The airplane was owned by Preiss Enterprises, Inc., and operated by United Flight Systems, Inc., both of College Station, Texas. Visual meteorological conditions prevailed for the Title 14 CFR Part 91 instructional flight for which a flight plan was not filed. The local flight departed from the Easterwood Field Airport (CLL), near College Station, Texas, approximately 30 minutes prior to the accident. The 750-hour flight instructor reported to the operator that "the engine started sputtering and lost power while the airplane was abeam the departure end of the runway while on a left downwind for runway 14." The flight instructor stated that he intended to land the airplane on a short taxiway perpendicular to the approach end of runway 32. During his approach to the taxiway, engine power was reestablished, and he elected to initiate a climb to return to home base. The flight instructor added that the engine lost power again during climb out, "and the airplane stalled." The airplane impacted on the shoulder of a highway, went through a fence, and came to rest in a field in the inverted position. Pilot/witnesses standing outside the terminal building at the airport reported that the airplane had been operating in the closed traffic pattern, performing touch-and-go landings on runway 14. They stated that when the airplane was established on a left downwind, abeam the south boundary of the airport, they heard the sound of the engine go from full power to idle. They observed the airplane make a left turn and descend toward the south end of the airport. The pilots commented that they expected the airplane to make a right turn and land downwind on runway 32. They reported that the flaps were extended to about 10 degrees. The witnesses added that the airplane continued to descend perpendicular to the runway, and crossed the approach end of the runway at an estimated altitude of 150 feet agl. When the airplane was just a few feet above the ground, the witnesses heard the sound of an increase to what sounded like full takeoff power. The airplane initiated a climb until it reached the southwest boundary of the airport, which was paralleled by a 25-foot-tall powerline. At powerline level, the airplane abruptly assumed a nose high attitude and cleared the powerlines. After clearing the powerlines, "the left wing of the airplane dropped and the airplane appeared to stall and spin toward the ground." The airplane "fell almost vertically with the engine still running at full power." The 15-hour student pilot told one of the witnesses that he observed the powerlines in their flight path, and they "pulled up hard and barely missed them." Examination of the airplane by the operator revealed spar damage to both wings and structural damage to the vertical stabilizer and engine firewall. The operator estimated that the airplane had approximately 18 gallons of fuel on board at the time of the accident. The 1973 model airplane was not equipped with shoulder harnesses for either occupant. The flight instructor sustained minor facial injuries during the accident.