Weatherly 620 N90104 accident near Russellville, Alabama

Probable cause

The pilot's failure to see and avoid powerlines during low-altitude agricultural spraying flight operations.

NTSB analysis

The agricultural pilot was initiating an aerial application flight over a cotton field. On the first pass, in controlled flight, he approached the field in a westerly direction and struck power lines, a large tree, then crashed onto a corn field. The pilot was killed, a postcrash fire ensued, and the airplane was destroyed. An examination of the wreckage did not reveal evidence of a preexisting mechanical anomaly or malfunction.

Agricultural pilots routinely perform risky low-altitude maneuvers, and interactions with powerlines are not uncommon; these lines are difficult to see and avoid at the speeds of these flights.

The pilot's traumatic injuries would not have been immediately fatal, but he had no evidence of breathing during the postcrash fire (no soot and no carboxyhemoglobin). As a result, the medical examiner placed the primary cause of death as hypertensive cardiac disease. This disorder increases the risk of a cardiac arrhythmia, which can cause palpitations, shortness of breath, or fainting. Such an event would not be expected to leave any evidence at autopsy. However, the operational evidence points to controlled flight into the power lines rather than loss of control as might be expected with an acute cardiac event. In addition, given the thermal injuries sustained, whether or how much the pilot's heart disease contributed to this accident could not be determined from the available evidence although it likely contributed to his immediate death.

Additional medical findings included the pilot's monocular vision, obstructive sleep apnea, and prior use of cannabis in the hours or days preceding the accident. Although the pilot’s monocular vision could have made it even more difficult for him to see and avoid the powerlines, he had thousands of hours safely flying agricultural operations; therefore, it is unlikely his visual defect contributed to this accident. Concerning the pilot’s treated obstructive sleep apnea, all evidence he provided to the Federal aviation Administration demonstrated excellent compliance with his treatment regimen. Therefore, it is unlikely the pilot’s treated sleep apnea contributed to the accident. Finally, the absence of any psychoactive component or active metabolite of cannabis in the pilot’s blood with a reporting cut off of 1 ng/ml suggests his use was many hours before the accident and that it is unlikely he was impaired by the effects of the drug at the time of the accident.

Text from the NTSB. Open the NTSB docket for ERA19LA263 for the full record.