On June 7, 2018, about 1150 eastern daylight time, an experimental, amateur-built Searey, N907CB, was substantially damaged following a partial loss of engine power near Englewood, Florida. The student pilot was not injured. The airplane was operated by the pilot under the provisions of Title14 Code of Federal Regulations part 91 as a solo instructional flight. Visual meteorological conditions prevailed, and no flight plan was filed for the flight that originated at Buchan Airport (X36), Englewood, Florida and was destined for Airport Manatee (48X), Palmetto, Florida.The pilot reported that he flew the airplane earlier that morning for about 75 minutes with no anomalies noted. He landed at X36 and took a break for about 30 minutes. He fueled the airplane earlier that day and there were 13.6 gallons on board for takeoff from X36. He performed an engine runup at 3,500 rpm along the entire length of runway 30, then turned around for a takeoff on runway 12. After rotation, the pilot noted a partial loss of engine power. The airplane sank and struck a tree at the end of runway 12 before coming to rest in a lawn near the runway end.
An inspector with the Federal Aviation Administration (FAA) responded to the accident site and examined the wreckage. He reported that the fuselage and left wing sustained structural damage. Examination of the fuel system revealed that the fuel tank was "almost full." The see-through fuel filter was about ¾ full and the fuel inside was clean. The clear plastic fuel lines contained fuel and the fuel was clean.
The FAA inspector's examination of the engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The engine choke was examined and it operated normally. The engine was not equipped with a carburetor heat system. Internal continuity was established and there were no holes or leaks on the engine case.
The closest weather reporting facility was the about 6 miles north-northwest of the accident site. At 1155, the weather conditions reported at Venice, Florida Municipal Airport (VNC) included temperature 30° C and dew point 22° C.
An FAA carburetor icing probability chart indicated the temperature and dew point conditions were conducive to the formation of serious icing at glide power, and icing at glide and cruise power.
According to the FAA Pilot's Handbook of Aeronautical Knowledge, carburetor ice occurs due to the effect of fuel vaporization and the decrease in air pressure in the carburetor's venturi, which can cause a sharp temperature decrease in the carburetor. If water vapor in the air condenses when the carburetor temperature is at or below freezing, ice may form on the internal surfaces of the carburetor, including the throttle valve. This then restricts the flow of the fuel/air mixture and reduces engine power. Generally, the first indication of carburetor icing in an airplane with a fixed-pitch propeller is a decrease in engine rpm, which may be followed by engine roughness. Under certain conditions, carburetor ice can build unnoticed until power is added.