Air Tractor Inc AT-301 N4421S accident near Farnsworth, Texas

Probable cause

The partial loss of engine power for reasons that could not be determined because the postaccident engine examination revealed no anomalies.

NTSB analysis

The pilot of the agricultural airplane reported that, as he was beginning a spray pass, the airplane sustained a partial loss of engine power. He attempted to dump his chemical load but was unable to maintain altitude and executed a forced landing to a field. He said that the engine continued to run smoothly but at a reduced power setting during the event. Postaccident examination of the engine revealed no anomalies that would explain the partial loss of engine power. The temperature and dew point were within a range of susceptibility for carburetor icing during glide and cruise power settings. However, the sudden reduction of power with the engine continuing to run smoothly described by the pilot was not consistent with the gradual reduction in power and rough running typically associated with carburetor icing.

Text from the NTSB. Open the NTSB docket for CEN13LA341 for the full record.