N714BSCessna 150M · 1976

On January 13, 2012, about 1750 central standard time, a Cessna 150M airplane, N714BS, experienced a loss of engine power during cruise flight near El Dorado, Kansas. The private rated pilot, sole occupant, was not injured and the airplane sustained substantial damaged during the force landing. The airplane was registered to and operated by Prairie Air Service, Inc. Benton, Kansas. Day visual meteorological conditions prevailed and no flight plan was filed for the 14 Code of Federal Regulations Part 91 personal flight. The flight originated from the Lloyd Stearman Field Airport (1K1), at 1700.

The pilot reported that he wanted to try the winter climbing capabilities of the airplane, before taking it on a long cross-country flight. The pilot was then able to climb to 10,700 feet, but reported that he was only able to hold the altitude with the airplane in a nose high attitude. He then decided to descend to a lower altitude and reduced the throttle to the low end of the green rpm arc. He added that since the engine rpm’s was in green arc, he did not apply carburetor heat.

After descending to 8,000 feet, he applied engine power; however, he could only get about 1,500 rpm. The pilot added that he applied carburetor heat for over a minute, checked the throttle and mixture controls, but the engine rpm kept getting lower. He established best glide and picked a highway for the force landing, during which time the engine stopped windmilling. Just before landing he noticed a couple cars on the highway and instead of risking a collision; he sidestepped to a triangular shaped field for the landing. During the landing the nosewheel hit an embankment and the airplane flipped over, coming to rest inverted.

The responding Federal Aviation Administration (FAA) inspector reported that the airplane sustained substantial damage to the fuselage and vertical stabilizer.

After the airplane was recovered, an examination was conducted by the FAA inspector. The inspector reported that the airplane was fueled with automobile gasoline (Mogas). Fuel was present in the gascolator, and the carburetor heat box controls were free to operate. Sparkplugs from each of the cylinders were removed and appeared fuel soaked. The engine’s magnetos produced spark when rotated by hand. The engine exam did not reveal any preimpact mechanical malfunctions or anomalies that would have precluded normal engine operation.

A review of the carburetor icing probability chart, located in the FAA's Special Airworthiness Information Bulletin CE-09-35, dated June 30, 2009, and relevant meteorological data, revealed that the weather conditions for several airports near the accident site, were just outside favorable conditions for the formation of carburetor icing. Additionally, the chart listed in the information bulletin, is based off the use of aviation fuel rather than Mogas. Review of the air temperature and moisture content of the area, at 8,000 to 12,000 feet altitude, also reveal the conditions were not conducive to carburetor icing.

A review of Transport Canada’s publication, TP10737, The use of automobile gasoline (Mogas) in Aviation, dated March 31, 1993 noted that, “ Mogas is generally higher in volatility than Avgas. Mogas will thus absorb more heat from the mixing air when vaporizing, resulting in ice accumulation at higher ambient temperatures. The likelihood of carb icing while flying on Mogas is higher.”

A reason for the loss of engine power was not determined.