CEN20LA234

The pilot’s exceedance of the airplane’s critical angle of attack, which led to an aerodynamic stall and a loss of airplane control. Contributing was a partial loss of engine power for undetermined reasons.

The pilot reported that, during an aerial application flight, a partial loss of engine power occurred while he was performing the first climbing turn to reverse course. The airplane subsequently descended and impacted terrain in a nearvertical attitude. Postaccident examination of the engine and its components revealed no preimpact anomalies. The reason for the partial loss of engine power could not be determined with the available evidence for this accident investigation. Given the airplane’s near-vertical descent, it is likely that the pilot exceeded the airplane’s critical angle of attack during the climbing turn, which resulted in an aerodynamic stall and a loss of airplane control from which the pilot was unable to recover.

On June 17, 2020, about 1800 central daylight time, an Air Tractor AT-402 airplane, N1532H, was substantially damaged when it was involved in an accident near Pine Bluff, Arkansas. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The pilot reported that he was spraying applicant over a field and that a partial loss of engine power occurred when he began the first climbing turn to reverse course and make a second pass. The airplane subsequently descended and impacted terrain in a near-vertical attitude. The pilot also reported that the airplane owner had previously told him that the engine could potentially have 15% less power and had a history of engine problems. Maintenance log entries did not show a history of engine problems. Postaccident examination of the engine and its components discovered multiple signatures of rotational scoring and rubbing. The fuel control unit, fuel pump, starting flow control unit, overspeed governor, and propeller governor showed no preimpact anomalies but did show signs of contamination consistent with the presence of agricultural fertilizer. The engine case and components were damaged by impact.