History of Flight
On September 19, 2023, at approximately 1232 central daylight time, an Air Tractor AT-502B airplane, registration N502NB, was substantially damaged in an accident near New Rockford, North Dakota. The pilot was fatally injured. The flight was a Title 14 Code of Federal Regulations Part 137 aerial application operation to apply herbicide to a sunflower field about 5 feet tall.
Witnesses reported the airplane flew under power lines while applying the product. The top of the vertical stabilizer was sheared off by the power lines, but the airplane continued flying straight westbound. About 0.25 miles west of the power lines, the airplane entered a left-turning dive and subsequently impacted a cornfield. A Federal Aviation Administration (FAA) safety inspector noted the pilot had struck a power line with a different Air Tractor airplane the week before, which did not result in an accident. The loader stated the accident flight was the second of the day, loaded with 120 gallons of Jet A fuel and 473 gallons of herbicide.
Personnel and Meteorological Information
The pilot's logbooks were not available during the investigation. At the time of the accident, the sun was positioned at 160° with a relative elevation of 42°, and the airplane's flight path over the field was aligned with a magnetic heading of 270°.
Wreckage and Impact
The airplane came to rest inverted on a southerly heading about 15 feet from the initial impact point. Corn stalks at the initial impact area showed angular separations consistent with a propeller strike. All major components were located. A postimpact fire partially consumed the accessory case area of the engine, but there was no evidence of an in-flight fire. The airplane sustained substantial damage to both wings, fuselage, and empennage.
Both wing leading edges were crushed aft. The rudder separated from the vertical stabilizer and was found under the left wing; its control cables were impact-separated about 6 inches from the attach points. Flight control continuity was established through impact separations. The vertical stabilizer was partially separated from the fuselage, with wire impact marks about 18 inches below its top. An approximate 10-inch section of upper vertical stabilizer, with about an 8-inch section of wire deflector attached, was impact-separated. The wire deflector cable ends were consistent with tension overload separation; its forward nicopress sleeve remained attached but deformed, and about 154 inches of the wire deflector were not recovered.
The three-bladed propeller remained attached to the engine, with two blades attached to the hub and one separated. All blades exhibited leading edge damage and S-type deformation. The engine remained attached to the fragmented mount, with thermal damage confined to the accessory area. The exhaust duct case showed torsional deformation. Examination revealed no preimpact mechanical malfunctions or anomalies that would have precluded normal operation. A field download of a Garmin aera 510 unit and attempts to recover data from a Satloc G4 unit yielded no pertinent data.
Medical and Pathological Information
An autopsy by the University of North Dakota Forensic Pathology Office listed the pilot's cause of death as blunt force injuries of head and chest, with the manner of death as accident. Postmortem toxicological testing by the FAA Forensic Sciences Laboratory detected methamphetamine (26 ng/mL in aortic blood, 27 ng/g in liver tissue), amphetamine (22 ng/mL in aortic blood, 25 ng/g in liver tissue), and carboxy-delta-9-THC (5.8 ng/mL in liver tissue, not detected in aortic blood). The FAA classifies methamphetamine and amphetamine as "Do Not Issue/Do Not Fly" medications, and considers marijuana use unacceptable for pilots. The pilot reported no medication use or active medical conditions at his last FAA medical examination.
Tests and Research
A representative from the Western Area Power Administration reported that with ambient temperature and a power line temperature of 90°F, the power line height above ground level was 26.8 feet. The sunflowers in the field were about 5 feet tall, and the level flight profile height of the airplane was 13.75 feet. The clearance between the power line and the sunflowers was about 21.8 feet. Air Tractor reported that the wire deflector length is 164 inches (13.67 feet), made of 5/32-inch diameter MIL-DTL-83420 Type I non-jacketed wire rope, rated to a minimum breaking strength of 2,400 pounds.