N502NB

HISTORY OF FLIGHTOn September 19, 2023, about 1232 central daylight time, an Air Tractor AT-502B airplane, N502NB, was substantially damaged when it was involved in an accident near New Rockford, North Dakota. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight.

The purpose of the flight was to apply herbicide to a field of sunflowers that were about 5 ft tall. Witnesses reported that the airplane flew underneath power lines while applying the product and observed the top of the vertical stabilizer sheared off by the powerlines before the airplane continued to fly straight ahead westbound. About 0.25 miles west of the powerlines, the airplane made a left-turning dive and subsequently impacted a cornfield (see figure).

A Federal Aviation Administration (FAA) aviation safety inspector reported that the pilot struck a power line with an Air Tractor AT-402 airplane the week before the accident flight; however, the previous wire strike did not result in an accident. The loader for the operation reported that before departure for the accident flight, which was the second flight of the day, the airplane was loaded with 120 gallons of Jet A fuel and 473 gallons of herbicide.

Figure. Annotated photo of the accident site (wreckage photo by the NTSB and vertical stabilizer section photo by the FAA). PERSONNEL INFORMATIONThe pilot’s logbooks were not made available during the investigation. METEOROLOGICAL INFORMATIONThe airplane’s flight path over the field was generally aligned with a 270° magnetic heading. At the time of the accident, the sun was positioned about 160° with a relative elevation of 42° above the horizon. WRECKAGE AND IMPACT INFORMATIONThe airplane came to rest inverted on a southerly heading about 15 ft from the initial impact point. Numerous corn stalks at the initial impact area exhibited angular separations consistent to that of a propeller strike. All major components were located.

A postimpact fire partially consumed the accessory case area of the engine. There was no evidence of an in-flight fire. The airplane sustained substantial damage to both wings, the fuselage, and the empennage.

Both wing leading edges were crushed aft. The rudder separated from the vertical stabilizer and was located underneath the left wing. The rudder control cables were impact-separated about 6 inches from their rudder attach points. Flight control continuity was established from the cockpit to the flight controls through impact separations.

The vertical stabilizer was partially separated from the fuselage and exhibited wire impact marks about 18 inches below the top of the vertical stabilizer. An approximate 10-inch section of upper vertical stabilizer, with about an 8-inch section of wire deflector attached, was impact separated from the assembly. The separated ends of the wire deflector cable were consistent with tension overload separation. The wire deflector cable’s forward nicopress sleeve remained attached to its forward attach point; the nicopress sleeve was deformed and the separated-ends of the cable were consistent with tension overload. About 154-inches of the wire deflector was not recovered.

The three-bladed propeller remained attached to the engine. Two propeller blades remained attached to the hub and one was separated. The three propeller blades exhibited leading edge damage and S-type deformation. The engine remained attached to the fragmented engine mount. Thermal damage from the post-impact fire was contained to the accessory area of the engine. The exhaust duct case exhibited torsional deformation. Examination of the airplane and engine did not reveal any preimpact mechanical malfunctions or anomalies that would have precluded normal operation.

A field download of a Garmin aera 510 unit revealed that there was no data pertinent to the accident flight. The NTSB Vehicle Recorder Laboratory was unable to recover any data from the Satloc G4 unit. MEDICAL AND PATHOLOGICAL INFORMATIONThe University of North Dakota Forensic Pathology Office, Grand Forks, North Dakota, performed the autopsy. The pilot’s cause of death was listed as blunt force injuries of head and chest, and his manner of death was accident.

Postmortem toxicological testing performed by the FAA Forensic Sciences Laboratory detected methamphetamine at 26 ng/mL in aortic blood and at 27 ng/g in liver tissue, as well as amphetamine at 22 /mL in aortic blood and at 25 ng/g in liver tissue. Carboxy-delta-9-THC was detected at 5.8 ng/mL in liver tissue and was not detected in aortic blood.

The FAA considers methamphetamine and amphetamine to be “Do Not Issue/Do Not Fly” medications. Marijuana is a federal Schedule I controlled substance, and the FAA considers its use by pilots unacceptable, regardless of state laws.

The pilot reported no medication use and no active medical conditions at the time of his last FAA medical examination. TESTS AND RESEARCHA representative from the Western Area Power Administration reported that with the ambient temperature and the temperature of the power line at 90° Fahrenheit, the measurement of the power line above the ground level was 26.8 ft.

The measurement of the sunflowers standing in the field was about 5 ft tall, and the level flight profile (overall height) of the airplane was 13.75 ft. The measurement between the power line and the sunflowers was about 21.8 ft.

Air Tractor reported that the length of the wire deflector is 164-inches or 13.67 ft and is made of a 5/32-inch diameter MIL-DTL-83420, Type I – non-jacketed wire rope, Composition B – corrosion resistant steel cable, rated to a minimum breaking strength of 2,400 pounds.