Air Tractor AT602 N2033N accident near David City, Nebraska

Probable cause

The pilot’s exceedance of the airplane’s critical angle of attack while maneuvering at low altitude, which resulted in an aerodynamic stall and impact with terrain.

NTSB analysis

The commercial pilot was performing an aerial application flight when the airplane struck the ground in a right wing low, 60° nose-down attitude. Flight track data from an onboard aerial guidance system revealed that the airplane had completed 6 previous aerial applications that morning, and was engaged in a seventh application when the accident occurred. During the last application, the airplane made 4 passes followed by shallow turns to reverse direction. During these turns, the airplane climbed until it reached 90° abeam the direction of application, then descended as it completed the turn on the opposite heading. The accident occurred during the turn between the fourth and fifth passes. Postaccident examination of the airframe, engine, and propeller revealed no evidence of any mechanical malfunctions or anomalies that would have precluded normal operation. The flap actuator was found extended 3-7/8 inches, correlating to a flap extension of 30°.

Based on the recorded data, the characteristics of the airplane's last turn before impact did not vary greatly from that of the other turns performed during the accident flight. It is likely that, during the turn, the pilot allowed the airspeed to decay and the airplane exceeded its critical angle of attack, which resulted in an inadvertent aerodynamic stall at an altitude which did not allow for recovery.

Text from the NTSB. Open the NTSB docket for CEN16LA291 for the full record.