N43310Keuthan Aircraft BUCCANEER II · 1994

On April 24, 2020, about 1045 central daylight time, a Keuthan Aircraft Corp. Buccaneer II, N43310, was substantially damaged when it was involved in an accident near Coden, Alabama. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot, he mixed automobile gas with oil and departed from his grass airstrip with full fuel tanks, which was about 10 gallons of fuel. He was flying in the local area over water at 800 ft when "the engine began to lose power, rpm started a slow continuous drop." He moved the throttle to full power, but the engine continued to lose rpms and airspeed. About 150 ft above ground level (agl), the "engine quit," and he attempted to glide to a small island. About 25 ft agl, the right wing stalled first, the airplane rolled right, and the nose dropped. The airplane impacted power lines, and then terrain. During the 1 hour 15-minute flight, he reported the engine performance was normal prior to the loss of power.

A Federal Aviation Administration (FAA) inspector responded to the accident scene and noted that the fuel tank contained about 2 gallons of fuel. Fuel was also present in both carburetor bowls. The fuel and fuel filter were free of debris and contaminates. The engine's crankshaft was manually rotated by turning the propeller, and continuity of the crankshaft and compression of each cylinder was confirmed.

A detailed examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. An engine run was performed, and the engine started immediately, accelerated smoothly, and ran continuously at all selected power settings without interruption. The airplane was not equipped with carburetor heat system.

At 1040, the weather reported at Mobile Downtown Airport (BFM), about 16 miles from the accident site, included a temperature 24°C and dew point 14°C. The calculated relative humidity at this temperature and dewpoint was 53%. Review of the icing probability chart contained in Federal Aviation Administration (FAA) Special Airworthiness Information Bulletin CE-09-35 revealed that the weather conditions at the time of the accident were "conducive to serious icing at glide [idle] power."

According to FAA Advisory Circular 20-113, "To prevent accidents due to induction system icing, the pilot should regularly use [carburetor] heat under conditions known to be conducive to atmospheric icing and be alert at all times for indications of icing in the fuel system." The circular recommended that when operating in conditions where the relative humidity is greater than 50%, "…apply carburetor heat briefly immediately before takeoff, particularly with float type carburetors, to remove any ice which may have been accumulated during taxi and runup." It also stated, "Remain alert for indications of induction system icing during takeoff and climb-out, especially when the relative humidity is above 50 percent, or when visible moisture is present in the atmosphere."

The pilot completed Pilot/Operator Aircraft Accident/Incident Report (NTSB form 6120.1/2) and reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation. Furthermore, in the "Operator/Owner Safety Recommendation" section of the report he stated that "manual carburetor heat should be added to all 2 stroke engines."

The Rotax 582 installation manual states, "operation in climatic conditions, where carburetor icing is likely to occur, a heating system must be fitted."