On July 27, 2002, about 1130 mountain standard time, an Air Tractor AT-502, N293JK, collided with mountainous terrain while maneuvering in a box canyon approximately 13 miles southwest of San Manuel Airport , San Manuel, Arizona. Devil Dusters, Inc., was operating the airplane under the provisions of 14 CFR Part 137. The commercial pilot, the sole occupant, sustained minor injuries; the airplane sustained substantial damage. The local aerial application flight departed San Manuel about 1115. Visual meteorological conditions prevailed, and a flight plan had not been filed. In a telephone conversation with the National Transportation Safety Board investigator-in-charge, the pilot reported that the purpose of the flight was to seed a fire devastated portion of the Coronado National Forest. The area where he was applying seed was in a box canyon that he had flown into several times, in days prior. After successfully completing a seed run, near the closed end of the canyon, he began a course reversal turn. About halfway through the turn, the airplane experienced a rapid loss of altitude. He ascertained that the airplane would not be able to complete the turn, and leveled the wings. The airplane stalled, and collided with flat terrain on the side of the mountain. He thought the loss of altitude that he experienced was the result of mountain downdrafts. The pilot reported no preimpact mechanical malfunctions or failures with the airplane.