On May 1, 2000, at 1858 Pacific daylight time, an Air Tractor AT-802A, N90802, main landing gear collapsed during landing roll at the Kingman, Arizona, airport. The airline transport certificated pilot, the sole occupant, was not injured. The airplane was substantially damaged. The flight departed from Eagle Airpark, Bullhead City, Arizona, about 1840. The repositioning flight of the agricultural application aircraft was operated under 14 CFR Part 91 by Eagle Aviation. Visual meteorological conditions prevailed and no flight plan was filed. The pilot told an inspector from the Federal Aviation Administration (Las Vegas, Nevada) Flight Standards District Office (FSDO) that the landing gear strut collapsed unexpectedly, and without warning, during the landing roll, and the airplane ground looped to the right. It was not subjected to an abnormal load during landing and the airplane was relatively light with no chemical load aboard and about 1,300 pounds of fuel. The inspector examined the airplane and said the left landing gear leaf broke inside the saddle. There was rust and beach marks in the fracture face indicative of a pre-existing crack. The model year 2000 airplane had about 1,100 hours total flying time and had recently received a 100-hour maintenance inspection; however, the inspector said the area where the crack occurred was difficult to inspect. The FSDO inspector said the left landing gear strut, a single spring steel leaf, separated in the shoulder area where the strut enters the saddle at the fuselage skin line. The left landing gear wheel was broken in the outboard flange area and the tire was deflated. The tire exhibited deep radial scratch marks on the outboard side wall. The aileron hinge bracket at the left wing tip was bent inboard and striations on the left wing lower surface were oriented spanwise. The left wing outer half-span was bent upward accompanied by compression wrinkling of the upper wing skin. Examination of the fracture by a metallurgical laboratory revealed that the strut met the manufacturer's chemical, hardness, and materials specifications for the component. The fracture through the strut was characterized by two distinct modes. The first was 0.08 inches in depth and 0.37 inches in width and exhibited features consistent with fatigue. The fatigue crack had multiple initiation sites along the top surface in an area that had fretting damage. The remainder of the fracture face displayed gross overload features. According to the laboratory report, the transverse failure of the strut resulted from an overload condition, with high side and drag loads, well in excess of the design ultimate load for the component. The complete metallurgical report is in the docket for this accident.