On July 7, 2013, at 1050 central daylight time, a Flight Design GmbH model CTLS light-sport airplane, N549LS, was substantially damaged during a forced landing near Sandwich, Illinois. The commercial pilot and his passenger sustained minor injuries. The airplane was registered to and operated by a private individual, under the provisions of 14 Code of Federal Regulations Part 91, while on a visual flight rules flight plan. Day visual meteorological conditions prevailed for the pleasure flight that departed Creve Coeur Airport (1H0), St. Louis, Missouri, about 0912, and was en route to Waukegan Regional Airport (KUGN), Waukegan, Illinois.
The pilot reported that as the flight descended through 4,700 feet mean sea level the engine began to run rough and eventually lost complete power. He noted that the engine monitoring system indicated that there was no fuel flow, despite the airplane having 16 gallons of automobile fuel still available between the two wing tanks. The pilot reported that his several attempts to restart the engine were unsuccessful in restoring engine power. He requested radar vectors from air traffic control to the nearest airport; however, the airplane was unable to reach an airfield and a forced landing was made into a cornfield. The nose and main landing gear collapsed during the forced landing, which resulted in substantial damage to the forward fuselage.
Two Federal Aviation Administration (FAA) airworthiness inspectors examined the airplane which had been recovered from the cornfield. The postaccident examination revealed that airplane had ample amount of automobile fuel to sustain engine operation. The carburetor heat control was found in the OFF position. The engine started and ran without any anomalies for a period of about 2 minutes. The engine responded to throttle inputs during the operational test run with the electric fuel pump in the OFF position. Additional examination of the fuel system filter, gascolator bowl, and the two carburetor bowls revealed no particulate or water contamination. The postaccident examination did not reveal any mechanical or fuel system anomalies that would have prevented normal engine operation.
The nearest aviation weather reporting station was located at Aurora Municipal Airport (KARR), Sugar Grove, Illinois, about 13 miles northeast of the accident site. At 1052, the KARR automated surface observing system reported the following weather conditions: wind 210 degrees true at 10 knots, visibility 10 miles, sky clear, temperature 27 degrees Celsius, dew point 19 degrees Celsius, altimeter setting 30.02 inches of mercury. A postaccident upper atmosphere model indicated that the temperature and dew point at 5,000 feet msl was 17.2 degrees Celsius and 9.9 degrees Celsius, respectively.
The carburetor icing probability chart included in FAA Special Airworthiness Information Bulletin No. CE-09-35, Carburetor Icing Prevention, indicates that there was a serious risk of accumulating carburetor ice at descent engine power settings. The FAA Pilot's Handbook of Aeronautical Knowledge states that when conditions are conductive to carburetor icing that carburetor heat should be applied immediately and should be left on until the pilot is certain all the ice has been removed. Additionally, if ice is present the application of partial carburetor heat or leaving heat on for an insufficient time might aggravate the situation.
A Transport Canada report entitled The Use of Automobile Gasoline in Aviation, No. TP 10737, indicates that the likelihood of experiencing carburetor icing is higher when operating on automobile fuel. The report notes that automobile fuel has a higher volatility than aviation fuels and, as such, absorbs more heat from the mixing air while being atomized for engine consumption. The result is the potential for carburetor ice to be accumulated at higher ambient temperatures when compared to aviation fuels.
When asked if he had applied carburetor heat following the loss of engine power, the pilot replied that he had never used carburetor heat in the six years that he had flown the accident airplane. Additionally, he indicated that a vast majority of his flying experience was in fuel-injected airplanes, and as such, his memorized emergency procedures did not include the application of carburetor heat following a loss of engine power.