On August 30, 2002, approximately 1315 central daylight time, an Air Tractor AT-401 agricultural airplane, N9193Y, was substantially damaged when it impacted an oil pumping rig while maneuvering near Hearne, Texas. The commercial pilot, who was the sole occupant, sustained minor injuries. The airplane was registered to and operated by Corpora Aerial Service, Inc., of Hearne, Texas. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 CFR Part 137 aerial application flight. The local flight departed a private airstrip near Hearne at 1300. According to the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), the pilot reported that he was conducting an aerial application flight defoliating a cotton field, starting on the south side working to the north, making alternate spray passes in an east to west direction. The pilot also reported that an oil pumping rig was located approximately 8 to 10 passes into the field. On all passes leading up to the area where the pumping rig was located, the pilot said he observed the unit "not pumping, and remaining off on the down stroke." The pilot further stated that while making a westerly spray pass on the north side of the pumping rig, he began a slow climb to clear the obstable. The pilot reported that during the climb to clear the pumping rig his view was obstructed by the left wing, which subsequently impacted the rig's "horse head" on the up stroke, severing the outboard 6 to 8 feet of the wing. The pilot stated that the airplane began to roll violently to the left, and "determining that I could no longer maintain control of the airplane, I pulled the throttle back to idle and let the aircraft descend into the cotton field." The airplane impacted the ground in a left wing low, nose low attitude, separating the engine and severing the tail section. The airplane came to rest in an inverted position, and there was no post-impact fire. According to an FAA inspector who traveled to the accident site and interviewed oil company personnel, oil pumping rigs were very prevalent in the area, and the "horse head" (portion of the pump which rises and lowers) can rise approximately 10 feet when in the pumping mode. It was also reported that this particular pumping unit was on a timer and would shut off periodically.