On May 20, 2002, approximately 0740 central daylight time, an Air Tractor 402 agricultural airplane, N91660, sustained substantial damage while landing at a private grass airstrip near Hughes, Arkansas. The commercial pilot, sole occupant of the airplane, was not injured. The airplane was registered to and operated by Hutcherson Flying Service of Forrest City, Arkansas, under 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed for the aerial application flight, and no flight plan was filed. The flight originated from another private airstrip near Blackfish, Arkansas, at 0720. In the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), the pilot reported that while spraying a field, he was having trouble with three spray nozzles. There were numerous crops in the area that were susceptible to the chemical he was applying, prompting him to land at an alternate airstrip to repair the leaking nozzles. The pilot reported that after touching down, the "tail wheel locking mechanism failed" and he felt the airplane "kick to the left, like something had come loose back there." The airplane's left spray boom became entangled in the adjacent wheat crop, pulling it off the left side of the airstrip. The airplane ground looped, and came to rest in an upright position. The pilot stated that a week prior to the accident, he noticed problems with the tail wheel locking mechanism. The tail wheel bushings and fork were replaced, but "this didn't cure the problem." An FAA inspector, who responded to the accident site, reported the left lower wing was damaged, the fuselage was twisted, and the rudder, elevator, and both horizontal and vertical stabilizers had sustained damage.