N580TX

On April 3, 2017, about 1934 central daylight time, an amateur-built Aero Adventure Aventura UL amphibian airplane, N580TX, sustained substantial damage during a forced landing near Kitty Hawk Flying Field (TS67), Garden Ridge, Texas. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.The pilot reported that the purpose of the local area flight was to simulate water landings by flying low passes over a grass area alongside the western edge of runway 14/32 at TS67. The pilot reported that the flight departed about 1915 and that he completed several uneventful low passes before the accident. The pilot stated that the engine began to "sputter" about 300 ft above the ground while on a right crosswind leg for runway 32. The engine subsequently had a total loss of power and the propeller stopped rotating. The pilot established best glide airspeed and made a forced landing in a nearby clearing among trees. The pilot stated that the airplane landed hard on the hull with the main landing gear retracted.

A Federal Aviation Administration (FAA) inspector performed an examination of the airplane at the accident site. The hull and both wings were substantially damaged during impact. Flight control continuity was confirmed from the cockpit inputs to the individual control surfaces. The airplane's landing gear were positioned for a water landing. The emergency ballistic parachute recovery system was armed but had not deployed. The three fuel tanks (1 main, 2 auxiliary) contained automotive gasoline premixed with engine oil. The fuel system contained ample fuel and the fuel shutoff valve was open. The fuel filter assembly and both carburetors contained fuel. Engine crankshaft continuity was confirmed by rotating the propeller. The spark plugs exhibited features consistent with normal engine operation. The propeller remained attached to the crankshaft and appeared undamaged. One of the three propeller blades had punctured the fabric-covered aft fuselage during impact. The propeller was removed from the engine to facilitate an engine test run. The engine, a 55-horsepower Hirth model 3202, serial number 901269, started and ran at various engine speeds without any hesitation or anomalies. The postaccident examination and successful engine test run revealed no evidence of a mechanical malfunction or failure that would have precluded normal operation.

According to a carburetor icing probability chart contained in FAA Special Airworthiness Information Bulletin CE-09-35, entitled "Carburetor Icing Prevention", the recorded temperature and dew point were in the range of susceptibility for the formation of carburetor icing. The bulletin notes that if ice forms in the carburetor of a fixed-pitch propeller aircraft, the restriction to the induction airflow will result in roughness in engine operation and a drop in engine speed.

The airplane was not equipped with a carburetor heat system; however, the engine was equipped two Dell'Orto sliding carburetors. Carburetors that incorporate a variable-venturi design (e.g. sliding carburetors) are not generally prone to carburetor icing, according to Aircraft Powerplants, Fifth Edition by Bent/McKinley.