Air Tractor Inc AT-301 N3661B accident near Hogeland, Montana

Probable cause

Collision with the ground while maneuvering at low altitude for reasons that could not be determined because postaccident examination did not reveal any anomalies that would have precluded normal operation.

NTSB analysis

The pilot departed in the agricultural airplane shortly before sunrise to apply herbicide in a field about 18 miles from the departure airport. Witnesses located adjacent to the accident site next to the field to be sprayed heard the airplane approach, turn, and collide with the ground.

The airplane was loaded with fuel and herbicide, such that it was about 9 percent (565 pounds) over its maximum gross weight. No anomalies were noted with the engine or airframe that would have precluded normal operation, and propeller damage signatures indicated the engine was producing power at the time of impact. The flaps were in the fully extended position, contrary to the airplane manufacturer's recommendations for this phase of flight.

The airplane sustained high-energy impact damage consistent with a steep nose-down descent into the ground, possibly due to a stall-spin. The increased airplane load would have reduced the stall speed, and the use of full flaps would also have affected the airplane's handling characteristics during the turn; however, the investigation could not determine to what extent this played a role in the accident. The reason for the use of full flaps could not be determined.

Family members reported that the pilot was both under financial, work, and personal stress. One of his daughters reported that during a telephone conversation the week before the accident, the pilot sounded tired and in a state of malaise; during the conversation the pilot sounded "dis-jointed and out of character," and he stated that he was "getting tired of flying."

Toxicological testing revealed that the pilot was taking medication used for the symptomatic relief of depressive illness. While the dose in itself was not high enough to pose a hazard to flight, he did not declare either his use of it or the underlying condition on his most recent FAA medical certificate application 1 month before the accident. However, it could not be determined whether the underlying condition for which the pilot was being treated would have affected is flying ability.

Text from the NTSB. Open the NTSB docket for WPR11LA272 for the full record.