Narrative
During an agricultural operation, the pilot was applying fertilizer over a field. On the fifth pass, the pilot broke off the pass at midfield for an unknown reason. The pilot then lined up again on the same row that had been previously abandoned and continued the application normally until reaching the midfield point.
At that location, the flagman observed pronounced up-and-down fluctuations of the elevators. The airplane descended to the point where the flagman ducked out of the airplane's path. The pilot discontinued the fertilizer application as the airplane nearly impacted willow trees at the end of the field.
Witnesses observed the airplane executing a turn to reverse direction. During the turn, the airplane impacted the ground in a nose-down attitude while in a right turn.
Findings
Toxicological testing was negative, as were autopsy findings. No other factual details regarding the aircraft, operator, or environmental conditions were provided in the source.