Air Tractor Inc AT-502B N502NB accident near New Rockford, North Dakota

Probable cause

The pilot’s failure to maintain clearance from overhead power lines during an aerial application flight. Contributing to the accident was the pilot’s decision to fly under the power lines with a small area of clearance available for the airplane.

NTSB analysis

The pilot was conducting a low-level aerial application flight, spraying a field of sunflowers, when the accident occurred. Multiple witnesses reported that the airplane flew underneath power lines and then the top of the vertical stabilizer was sheared off by the power lines. The airplane continued to fly straight ahead, and about .25 miles west of the power lines, the airplane made a left-turning dive and subsequently impacted a cornfield. A postimpact fire partially consumed the accessory case area of the engine. The airplane sustained substantial damage to both wings, the fuselage, and the empennage.

Postaccident examination of the airframe and engine did not reveal any anomalies that would have precluded normal operation before the airplane impacted the power line. The torsional deformation observed on the engine’s exhaust duct case, combined with the propeller damage and evidence of propeller strikes on the terrain, indicates that the engine was producing power at impact. About 154-inches of the 165-ich wire deflector cable was not recovered. The separated ends of the cable sections attached to the fuselage and vertical stabilizer were consistent with tension overload separation. It is likely that the wire deflector cable’s impact with power line exceeded the cable’s minimum breaking strength.

Toxicological testing indicated that the pilot had used a cannabis product and methamphetamine. However, neither delta-9-THC nor its psychoactive metabolite was detected in the tested specimens, and the non-psychoactive metabolite carboxy-delta-9-THC was not detected in blood. This indicates that it is unlikely that effects of the pilot’s cannabis use contributed to the accident. Toxicological results also indicated that the pilot likely had used methamphetamine and was experiencing some methamphetamine effects at the time of the accident. Details of his methamphetamine use and specific associated effects at the time of the accident are unknown. Such effects may have ranged from improved reaction time to impaired judgment, perception, reaction, and control. Whether effects of the pilot’s methamphetamine use contributed to the accident could not be determined.

Based on the available evidence, the pilot likely misjudged the overhead clearance necessary to avoid the power lines. About 8 ft (about 4 ft on the top of the airplane and about 4 ft on the bottom of the airplane) clearance was available for the airplane to fly underneath the power lines and yet remain above the sunflowers.

Text from the NTSB. Open the NTSB docket for CEN23FA412 for the full record.