Air Tractor Inc AT-301 N73071 accident near Edgeley, North Dakota

Probable cause

The loss of engine power for reasons that could not be determined because postaccident examination of the airplane and engine did not reveal any anomalies that would have precluded normal operation.

NTSB analysis

The pilot reported that shortly after leveling off and making a power reduction for cruise flight, he noticed that a descent had developed. The pilot added one notch of flaps and dumped the chemical load using the emergency dump handle but the descent continued. He landed the airplane in a bean field. A postaccident examination of the airplane and engine did not reveal any anomalies, nor were any anomalies noted in the airplane’s recent annual inspection. The temperature and dew point recorded at a nearby airport were in a range susceptible to the formation of carburetor ice at glide and cruise power settings. Carburetor icing usually results in engine roughness and a drop in manifold pressure. Since the pilot made no mention of engine roughness, a decrease in manifold pressure, and was able to increase manifold pressure during his attempts to arrest the descent, it is unlikely that the power loss was due to carburetor icing. The reason for the power loss could not be determined.

Text from the NTSB. Open the NTSB docket for CEN11LA598 for the full record.