FTW02LA086 · Air Tractor AT-502B

The 9,978-hour commercial pilot had dispensed his 4th load of fertilizer for the day and was returning to the airstrip in clear weather when witnesses observed the airplane climb, nose over, and impact the ground in an inverted attitude in a furrowed field. Data from the Ag-Nav GPS indicated that the airplane climbed from 200 feet agl to approximately 480 feet agl and then vertical to approximately 630 feet agl prior to descending. According to the propeller manufacturer's representative, the propeller was operating with power "ON" at the time of impact, the propeller was operating at a blade angle in the "normal operating range," and there were no discrepancies found that would have precluded "normal" operation of the propeller prior to impact. No evidence of an in-flight mechanical and/or flight control malfunction was found that would have rendered the airplane uncontrollable prior to the impact. The FAA Civil Aeromedical Institute's (CAMI) Forensic Toxicological and Accident Research center examined the specimens taken by the medical examiner. The toxicological findings were positive for 0.023 (ug/ml, ug/g) Amphetamine detected in the blood; 0.892 (ug/ml, ug/g) Amphetamine detected in the urine; 0.053 (ug/ml, ug/g) Methamphetamine detected in the blood; and 2.516 (ug/ml, ug/g) Methamphetamine detected in the urine. Use of amphetamines would have precluded medical certification of this pilot had it been reported. The pilot was impaired either by the effects of methamphetamine, which may have led him to attempt to perform beyond his capabilities on the aircraft, or by withdrawal effects, which may have resulted in significant fatigue and distraction.

Verbatim NTSB analysis and probable cause from the NTSB dataset