On August 21, 2005, about 0930 central daylight time, a single-engine Cessna 172R airplane, N93AF, was substantially damaged during a forced landing following a loss of engine power near Springtown, Texas. The instrument rated private pilot, the sole occupant of the airplane, was not injured. The airplane was registered to and operated by American Flyers Schools, Inc., of Pompano Beach, Florida. Visual meteorological conditions prevailed and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The cross-country flight originated from the Meacham International Airport (FTW), near Fort Worth, Texas, at 0900, and was destined for the Levelland Municipal Airport (LLN), near Levelland, Texas. According to the pilot, after departing FTW he climbed to an altitude of 6,500 feet. While in cruise flight, approximately ten miles west of Springtown, Texas, he noticed a "mist" forming on the windscreen. He elected to return to FTW and began a descent. During the descent the oil pressure light illuminated and the pilot observed that the "oil temperature was very high." The pilot then elected to shut down the engine. Realizing that he could not reach the airport, he proceeded to search for a suitable landing area. After he attempted to contact Meacham tower to declare an emergency he selected a landing field. Observing power lines in his path, the pilot restarted the engine in an attempt to avoid contacting them. The airplane's "engine responded with very little effect," but the pilot was able to clear the power lines and landed in a field. During landing, the nose landing gear collapsed and the airplane nosed over, coming to rest in an inverted position. A Federal Aviation Administration (FAA) inspector responded to the accident site and reported that the airplane's wings, vertical stabilizer, and engine firewall had sustained structural damage. The inspector also reported that the engine oil sump contained approximately six quarts of engine oil at the time of recovery. An examination of the engine by representatives from the NTSB and Cessna Aircraft Company, revealed that the engine oil pressure switch, (P/N 83278), had failed internally which allowed engine oil to vent overboard. A review of the engine logbooks suggested that the total time on the pressure switch was approximately 5,321 hours. NTSB investigators manually rotated the engine and obtained thumb compression on all cylinders. The engine rotated freely and continuity was established to all valves and accessory case gears. The left and right magnetos produced spark through each spark plug lead to all spark plugs, with the exception of the number one cylinder top spark plug lead, which had sustained damaged during the accident. The Cessna 172R Skyhawk Information Manual dated December 2, 1996, page 3-20 stated: "If a total loss of oil pressure is accompanied by a rise in oil temperature, there is good reason to suspect an engine failure is imminent. Reduce engine power immediately and select a suitable forced landing field. Use only the minimum power required to reach the desired touchdown spot."