N73194Air Tractor AT-502 · 1988

The pilot stated that he listened to the airport’s automated weather station broadcast before taxi and, at that time, the surface wind was from 080° at 8 knots. However, while he taxied to runway 13 the airport’s windsock direction was consistent with a surface wind from the north-to-northeast. Before takeoff, he relistened to the airport’s automated weather station broadcast, which still reported the surface wind was from 080° at 8 knots. Believing the automated weather station report was accurate, the pilot continued with a takeoff on runway 13.

The pilot stated the takeoff was conducted with 10° of flaps extended but recalled that the takeoff roll was longer than normal. He kept the control stick full aft and to the left (into the wind) during the initial takeoff roll. After the airplane accelerated to 60 mph, he pushed the control stick forward to raise the tail, but the airplane suddenly veered left and off the left side of the runway into a drainage ditch. The pilot was unable to regain directional control with a full right rudder input. During the runway excursion, the right main landing gear separated which resulted in substantial damage to both wings when they impacted the ground. The pilot reported that there were no mechanical failures or anomalies with the airplane that would have prevented normal operation.

The pilot believes a left quartering tailwind may have contributed to his loss of directional control during takeoff. He also opined that the surface wind direction reported by the airport’s automated weather station was incorrect, which led him to believe using runway 13 was appropriate for the reported wind direction. A review of the airport’s automated weather station data revealed the reported surface wind direction was 080°-090° in the minutes before and after the accident. A postaccident weather model for the airport included an east-northeast surface wind (061°) at 4.5 knots. Based on the pilot’s windsock observation, the unintentional left veer during the takeoff roll was likely due to the pilot not maintaining directional control with a left quartering tailwind.