On May 19, 2004, an Air Tractor AT-401 (registration N4508Y) was involved in an aviation accident near San Angelo, TX. Investigators recorded the probable cause as: The loss of engine power for undetermined reasons. A contributing factor was the soft terrain encountered during the aborted takeoff. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During an aerial application takeoff, the engine gradually lost power. The pilot aborted the takeoff, and the airplane veered into a soft wheat field. Investigation found a bent carburetor flange and missing cotter key, but the reason for power loss was not determined.
Accident Details
During the takeoff phase of an aerial application flight, the engine gradually lost power. In response, the pilot aborted the takeoff. The airplane subsequently veered and came to rest in a soft wheat field.
Examination Findings
A post-accident examination of the airplane revealed several observations. Fuel was present at the fuel pump. The throttle and mixture linkages were intact. Engine continuity was established by rotating the propeller manually. Inspection of the carburetor showed that the top housing flange was bent, which resulted in an air leak. Additionally, the cotter key was missing from the economizer stud, and the stud was adjusted to a full rich setting at some point between the engine's overhaul and the accident. The fuel inlet screen, float bowl, and inlet needle were found to be free and clear of contaminants.
Investigation Outcome
Despite the documented anomalies, the reason for the loss of engine power was not determined.