NTSB Factual Report

On May 19, 2004, approximately 0645 central daylight time, an Air Tractor AT-401 single-engine agricultural airplane, N4508Y, sustained substantial damage when it impacted terrain following a loss of engine power during takeoff from a private airstrip near San Angelo, Texas. The commercial pilot, who was the sole occupant and registered owner of the airplane, was not injured. Visual metrological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 137 aerial application flight. The local flight was originating at the time of the accident.

According to an FAA inspector, the pilot reported that during takeoff of the first flight of the day, the engine gradually lost power. The pilot aborted the takeoff, and the airplane veered into a soft wheat field. Examination of the airplane revealed the main landing gear was damaged, and the left wing was partially separated. Fuel was observed at the fuel pump, the throttle and mixture linkages were intact, and engine continuity was established by rotating the propeller through by hand. According to the pilot, the carburetor "recently" had been overhauled. The carburetor was removed and shipped to the overhaul repair station for further examination.

On June 16, 2004, under the supervision of an FAA inspector, the Bendix NAY9E1 carburetor, serial number 5638771, was examined and disassembled at the overhaul repair station. Examination of the carburetor revealed the top housing flange was bent which resulted in an air leak. The cotter key was missing from the economizer stud and the stud was adjusted to a full rich setting at some time between the overhaul and the accident. The fuel inlet screen, float bowl, and inlet needle were free and clear of contaminants.

The reason for the loss of engine power was not determined.

NTSB Probable Cause

The loss of engine power for undetermined reasons. A contributing factor was the soft terrain encountered during the aborted takeoff.