HISTORY OF FLIGHT On July 3, 2011, about 2021 Pacific daylight time, a Cessna 180D, N6451X, was substantially damaged when it struck a telephone line that spanned across the Santa Clara River, about 1.8 miles south-southwest of the Santa Paula Airport (SZP), Santa Paula, California. The commercial pilot and his passenger were fatally injured. The airplane was registered to a private individual and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Dusk visual meteorological conditions prevailed and no flight plan was filed. The flight originated from SZP about 2000. A witness, who was a rated pilot, reported to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) that he was located at SZP, and observed the airplane during a portion of the accident flight. The witness stated that the accident pilot initiated the flight by performing a short field takeoff and performed two circuits around the traffic pattern. During the third takeoff, the airplane turned left, overflew the south side of the airport, and proceeded toward the Santa Clara River at an approximate altitude of about 100 feet above ground level (agl). The witness further stated that the airplane did not gain additional altitude, and that he lost sight of the airplane while it was flying in a westerly direction over the river. During the entire time the witness observed the airplane, its engine sounded normal. A witness standing on a hillside about 450 feet south-southeast of the accident site reported to the NTSB IIC that he heard the airplane's engine for a few seconds before the crash. The witness stated that he did not observe the accident sequence, however, immediately after the engine sound stopped, he observed a fire in the Santa Clara River bed. The witness immediately proceeded toward the fire and observed the accident airplane engulfed in flames. PERSONNEL INFORMATION The pilot, age 43, held a commercial pilot certificate with airplane single-engine land and instrument airplane ratings. A second-class airman medical certificate was issued to the pilot on July 6, 2010, with no limitations stated. The pilot reported on his most recent medical certificate application that he had accumulated 1,930 total flight hours. AIRCRAFT INFORMATION The four-seat, high-wing, conventional gear airplane, serial number (S/N) 18050951, was manufactured in 1960. It was powered by a Continental O-470-L (10) engine, serial number 069734-R, rated at 230 horse power. The airplane was also equipped with a McCauley adjustable pitch propeller. The most recent annual inspection was completed on February 15, 2011, at a total airframe time of 3,596.8 hours. The airframe, engine, and propeller logbooks were not located during the investigation. METEOROLOGICAL INFORMATION A review of recorded data from the Camarillo Airport automated weather observation station, located 6.8 miles south of the accident site, revealed at 1955, conditions were wind from 210 degrees at 5 knots, visibility 9 miles, sky clear, temperature 18 degrees Celsius, dew point 15 degrees Celsius, and an altimeter setting of 29.77 inches of mercury. According to data from the United States Naval Observatory, official sunset occurred at 2012, with the end of civil twilight at 2042. WRECKAGE AND IMPACT INFORMATION Examination of the accident site revealed that a downed telephone line, which was oriented in a north-south direction, spanned across the Santa Clara River between two poles. The wires were about 85 feet in height above the ground and both poles on either side of the river were about 15 feet higher than the telephone line. No line marking balls were observed. Airplane components consisting of wing tips, shattered navigation light lens fragments, plexiglas windscreen, and ground scar were located over an estimated 175-foot-long distance beginning about 180 feet southwest of the downed telephone line, oriented on a heading of about 220 degrees magnetic. Examination of the airframe revealed that the airplane's entire fuselage, including the cockpit and instrument panel, were consumed by a post ground impact fire. A cable mark was noted on the right wing leading edge about 12 inches outboard of the flap/aileron split. The mark was oriented approximately 45 degrees to the leading edge of the wing, inboard on the top of the wing to outboard on the bottom of the wing. Flight control continuity was established throughout the airplane to all primary flight control surfaces. Examination of the engine revealed that it was separated from the engine mount structure. The wye-ducting, carburetor, and an induction elbow were separated from the engine and located within the wreckage debris path. The engine exterior surfaces exhibited thermal discoloration. The magnetos remained attached to the engine and exhibited thermal discoloration to their housings. The cylinders were examined using a borescope and the piston heads and combustion chambers exhibited dark grey deposits. The valve heads were unremarkable. The crankshaft was rotated by hand and thumb compression was obtained on all six cylinders. Engine and valve train continuity was established throughout the engine. Spark was observed from all ignition leads while the crankshaft was rotated. The propeller remained attached to the crankshaft propeller flange and exhibited score marks in a chordwise direction, leading edge nicks and torsional deformation. MEDICAL AND PATHOLOGICAL INFORMATION The Ventura County Medical Examiner conducted an autopsy on the pilot on July 4, 2011. The medical examiner determined that the cause of death was “...thermal injuries with smoke/soot inhalation.” The FAA's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, performed toxicology tests on the pilot. According to CAMI's report, carbon monoxide, cyanide, volatiles, and drugs were tested, and had positive results for 18 percent carbon monoxide detected in blood.