Air Tractor Inc AT 502B N879JA accident near Dighton, Kansas

Probable cause

The pilot's failure to follow the Preflight checklist and his inadequate preflight inspection, during which he failed to detect the water contamination of the fuel, which resulted in a partial loss of engine power during initial climb.

NTSB analysis

The commercial pilot stated that he did not observe any anomalies during his preflight inspection or during his before-takeoff engine run-up. The pilot was departing on a positioning flight when the engine lost partial power during initial climb. The pilot's corrective actions did not restore full engine power, so he made a forced landing to a nearby muddy field. The pilot reported that, after the accident, the engine continued to run with a gas generator speed of about 35% and that he cut fuel flow to the engine to shut it down.

Postaccident engine examination revealed no evidence of a mechanical malfunction that would have precluded normal operation; however, an examination of the fuel system revealed water contamination in multiple tanks and filters. Laboratory testing showed that the observed water contamination exceeded the allowable limits for aviation turbine fuel. Given the amount of water contamination observed after the accident, it is likely the pilot did not adequately check the fuel condition at both wing fuel tanks, header fuel tank sump, and the fuel valve sump as required by the airplane flight manual's Preflight checklist.

Text from the NTSB. Open the NTSB docket for CEN15LA226 for the full record.