CEN11LA539

About 25 minutes prior to reaching the intended refueling destination, the pilot noticed a drop in engine rpm. The pilot applied carburetor heat, the engine rpm increased, and he turned the carburetor heat off. All other engine instruments and indications appeared normal. During the descent, the engine rpm dropped again, and the pilot attempted to resolve the problem by again applying carburetor heat, changing throttle positions, and switching fuel tanks; however, he was unsuccessful. Unable to maintain altitude, the pilot performed a forced landing to a cornfield. During postaccident examination of the airplane, fuel was noted in the airframe fuel tanks, and mechanical continuity was established throughout the engine. The airplane was operating in conditions conducive to serious carburetor icing at glide power at the time of the accident. It is possible that, when the engine lost partial power during the descent, the carburetor heat was not effective, because the engine was operating at a low power setting and was not producing sufficient heat to melt the ice.

On July 29, 2011, at 1030 central daylight time, a Hurley Cavalier SA 102.5 experimental amateur-built airplane, N115RH, sustained substantial damage when it impacted terrain near Salem, Iowa. The commercial pilot, who was the sole occupant and registered owner, sustained serious injuries. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The flight departed Oshkosh, Wisconsin, approximately 0830, and was destined for the Mount Pleasant Municipal Airport (MPZ), Mount Pleasant, Iowa. Approximately 25 minutes prior to reaching the intended refueling destination, the pilot noticed a drop in engine RPMs. The pilot applied carburetor heat and the engine RPMs increased. At that time, all other engine instruments and indications appeared normal. During the descent to MPZ, the engine RPMs dropped again, and the pilot attempted to resolve the problem by applying carburetor heat, changing throttle positions, and switching fuel tanks; however, he was unsuccessful. Unable to maintain altitude, the pilot initiated a forced landing to a cornfield. A postaccident examination of the airplane showed both wings spars were bent and the fuselage was buckled. Fuel was noted in the airframe fuel tanks and the carburetor was separated from the engine. Mechanical continuity was established throughout the engine. No anomalies were noted with the airframe or engine that would have precluded normal operations. At 1035, the MPZ automated weather observing system (AWOS), located approximately 5 miles north of the accident site, reported the wind from 060 degrees at 5 knots, visibility 10 statute miles, scattered clouds at 1,700 feet, temperature 81 degrees Fahrenheit, dew point 73 degrees Fahrenheit, and an altimeter setting of 30.05 inches of Mercury. According to the Federal Aviation Administration's Special Airworthiness Information Bulletin CE-09-35 Carburetor Icing Prevention chart, with the temperature and dew point, 81 degrees Fahrenheit and 73 degrees Fahrenheit respectively, conditions were conducive for serious carburetor ice at glide power.