HISTORY OF FLIGHT On August 9, 1993, at 1217 central daylight time, a Mooney M20C, N5672Q, was destroyed upon impact with terrain while on pipeline patrol near Big Lake, Texas. The airline transport pilot, sole occupant of the airplane, was fatally injured. Visual meteorological conditions prevailed for the aerial observation flight. There were no witnesses to the accident. The wreckage was discovered by the Reagan County Fire Department after they arrived at the site responding to a call to a grass fire. The pilot, operating as Elkin Aviation, was working as an independent contractor for the Exxon Pipeline Company. The assigned patrol consisted of the route known as "the Yates-Pecos to Kemper crude." According to the pipeline company, the pilot was very familiar with the assigned route, and had been flying the route on a weekly basis. Other pipeline patrol pilots interviewed stated that this type of flight was normally flown at 500 feet above ground level. AIRCRAFT INFORMATION The pilot, a certified airframe and powerplant mechanic, performed the last complete engine overhaul on February 1, 1992. According to the engine logbook, he also performed a "top overhaul" at the time of the last annual inspection. The airplane was filled to capacity with 100LL aviation fuel at the Crane County Municipal Airport, Crane, Texas. A witness at the airport stated that the engine backfired several times before the pilot was able to start the engine. The witness added that the engine appeared to be running rough while the airplane taxied for departure, as well as during the initial takeoff climb. WRECKAGE AND IMPACT INFORMATION The wreckage path went through mesquite trees on a measured heading of 150 degrees, and 20 degree nose down, 200 feet west of the pipeline being patrolled. The separated left wing was found 36 feet from the initial ground scar. The wreckage was scattered in a linear pattern over a distance of 450 feet from the initial point of impact. All aircraft components and wreckage were found within 50 feet of either side of the centerline of the wreckage linear pattern. See enclosed wreckage diagrams. The airplane was found with the landing gear and the wing flaps retracted. All flight controls were accounted for at the accident site. Flight control continuity was established to both ailerons. Continuity to the rudder and the elevator could not be established forward of the rear of the cabin due to fire damage. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy and toxicological tests were ordered and performed. The autopsy was performed by the Bexar County Forensic Science Center in San Antonio, Texas, on August 10, 1993. Toxicological tests were negative. FIRE A post-impact fire destroyed the cockpit and cabin area of the airplane. A locally manufactured 36 gallon auxiliary fuel tank bolted to the floor of the baggage compartment separated from the airframe and was located 69 feet from the main wreckage. According to fire department personnel responding to the fire, an explosion was heard as the first fire fighting vehicle was approaching the accident site, and a very intense fire was still burning from the fuel cell upon their arrival. The fuel selector and all connecting lines from the auxiliary fuel system were destroyed by fire. No evidence of pre-impact fire was found during the investigation. TEST AND RESEARCH The engine was found separated from the airframe, and was examined at the accident site. The carburetor, oil reservoir, and propeller, were found separated from the engine. Engine continuity was established, the ignition system was tested, and evidence of lubrication was noted throughout the engine. The oil pressure and oil suction screens were free of metal particles. The vacuum pump shaft was found sheared, with the lower housing bolt missing. Evidence of oil seepage was found at the point where the bolt was missing. No other anomalies were found with the engine assembly. The propeller assembly was found sheared at the propeller flange. Both blades exhibited S-bending and twisting. The leading edges of both blades exhibited dents and gouges. The outer two inches of one of the propeller blades separated from the propeller, and was found among rocks at the initial point of ground impact. ADDITIONAL DATA The airplane was released to the owner's representative at the accident site on August 11, 1993.