Air Tractor AT-402B N61318 accident near Deerfield, Kansas

Probable cause

The pilot inadvertently stalling the airplane. Contributing factors in this accident were the pilot intentionally performing low altitude maneuvers (side slips), unporting and starving the engine of fuel, and his initiating a climb at low airspeed.

NTSB analysis

The pilot had noticed a fuel imbalance of almost a quarter of a tank after the previous spray flight. The airplane was then serviced with 40 gallons of Jet A fuel through a single point refueling port. The pilot checked the fuel level again and noted the right tank had approximately 1-1/2 inch more fuel than the left tank, or roughly 1/2 capacity in the left tank and between 1/2 and 2/3 capacity in the right tank. He took off with 375 gallons of chemical mix to spray two corn circular fields. He used a left hand reverse racetrack pattern to spray the two circles. Halfway through the application, he checked the fuel gauges and noted both were reading between 1/4 and 1/2 tank. On his final swath of the field, the pilot climbed over a set of power lines. It was his intention to utilize the southerly wind to drift the spray under the power lines to the edge of the field. He performed a right side slip maneuver (right wing down, left rudder) to spray the west circle, leveled his wings, and repeated the maneuver to spray the east circle. He then initiated a 60-degree bank right climbing turn from a height of about 30 feet. The pilot said that during the climbing turn, "altitude and decrease in airspeed felt normal." He looked out the right side of the airplane to check the spray pattern. When he attempted to level the wings at an altitude between 100 and 150 feet, the right wing "continued to drop followed by the nose." He said the stall warning horn never sounded, and there was no aerodynamic buffet. He opened the throttle completely, but the engine did not respond. The airplane struck a pivotal sprinkler and impacted terrain. It was the pilot's opinion that the engine lost power "due to unporting of fuel from the tank to the engine [induced] by the slip maneuver."

Text from the NTSB. Open the NTSB docket for DEN08LA125 for the full record.