ERA24LA032

The pilot was preparing for takeoff after the engine had been running for about 25 minutes. Before departing, he tested the carburetor heat and noted that it was functioning as expected. He applied power for takeoff and the engine accelerated “strongly and smoothly.” About 25-30 ft above the ground during the initial climb the engine suddenly lost about 1,000 rpm. The pilot elected to perform an off-field landing. He maneuvered to avoid a hedgerow and the airplane touched down in an in an area of high grass. During the landing sequence, the fuselage and right wing were substantially damaged. A postaccident examination of the engine and fuel system did not reveal evidence of a preexisting anomaly or failure that would have precluded normal operation. The temperature/dew point at the time of the accident was in the range for serious carburetor icing at cruise power. While the pilot described checking the functionality of the carburetor heat before as part of his normal preflight checks, and leaving it on for “a little longer” than normal as a part of that process, given all available information, it is likely that the temperature of the carburetor dropped during the extended operation of the engine while on the ground, and that during takeoff, the carburetor accumulated ice to a point that resulted in the partial loss of engine power.

On November 11, 2023, about 0815 eastern standard time, a Taylorcraft BC12-65 airplane, N29868, was substantially damaged when it was involved in an accident near Columbia, Tennessee. The private pilot incurred minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that he performed a preflight inspection of the airplane and confirmed there were about 12 gallons of fuel on board. Including engine start, taxi, and pretakeoff runup operations, the engine was running for about 25 minutes with no anomalies noted. Before takeoff he activated the carburetor head and noticed a “normal” engine rpm drop. He also stated that he left the carburetor heat applied, “for a little longer” and when he turned it off there was no engine rpm change. He applied power for takeoff and the engine accelerated “strongly and smoothly.” About 25-30 ft above the ground during the initial climb, the engine suddenly lost about 1,000 rpm. The pilot elected to perform an off-field landing. He maneuvered to avoid a hedgerow and the airplane touched down in an area of high grass. During the landing sequence the airplane was substantially damaged. The pilot was met by first responders. The wreckage was examined after recovery to a storage facility. The wing and main fuel tanks contained fuel and were uncompromised. Fuel drained from the tanks was clean and free of water or other contaminants. The carburetor bowl contained a small amount of particulate matter. The carburetor inlet screen was clear. The engine was turned through manually by rotating the propeller. Compression and suction were noted on all four cylinders and valve action was correct. The magnetos produced spark to all leads when operated manually. The spark plugs were normal in color and wear when compared to a Champion inspection chart. The carburetor was broken from the engine consistent with impact damage; however, the cockpit controls remained attached. The carburetor heat knob was found in the “off” position. Examination of the fuel system and engine did not reveal evidence of a preexisting anomaly or failure that would have precluded normal operation. The recorded temperature and dew point near the accident site was about 48 and 35 degrees, respectively. On a carburetor icing probability chart, those temperatures were in the “serious icing – cruise power” range. FAA Special Airworthiness Information Bulletin (CE-09-35) – Carburetor Icing Prevention, stated that: “…pilots should be aware that carburetor icing doesn't just occur in freezing conditions, it can occur at temperatures well above freezing temperatures when there is visible moisture or high humidity. Icing can occur in the carburetor at temperatures above freezing because vaporization of fuel, combined with the expansion of air as it flows through the carburetor, (Venturi Effect) causes sudden cooling, sometimes by a significant amount within a fraction of a second. Carburetor icecan be detected by a drop in rpm in fixed pitch propeller airplanes and a drop in manifold pressure in constant speed propeller airplanes. In both types, usually there will be a roughness in engine operation.”