On August 13, 2006, at 1315 Pacific daylight time, an experimental Sicheneder Pitts S1S, N22JF, nosed over during landing at Tracy Municipal Airport, Tracy, California. The pilot/owner was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. The commercial pilot was not injured; the airplane sustained substantial damage. The personal flight departed Byron Airport, Byron, California, at 1300. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot stated in a written report that as he approached Tracy, he checked the Automated Weather Observation System, and visually established contact with two other aircraft in the pattern. He then joined the pattern and established the airplane for a landing on runway 30. He performed a three point landing within the first 1,000 feet passed the threshold. He stated that he landed just right of the centerline, and during rollout encountered a dip in the runway. He felt the landing gear 'flex' and the airplane then veered to the left. He attempted to correct with right rudder and brake, but the airplane nosed over. The airplane sustained substantial damage to the lower right wing, upper left wing, and the vertical stabilizer.