On December 28, 2003, at 1400 eastern standard time, an unregistered homebuilt Rans S-17, was substantially damaged while maneuvering near Woodstock, Connecticut. The uncertificated pilot was seriously injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under 14 CFR Part 91. According to the pilot, he departed a private airstrip about 1315 with about 5.5 gallons of fuel onboard. After 45 minutes of flight time the pilot was flying at 400 feet above the Geer Christmas Tree Farm, located in Woodstock. "Suddenly and without warning," and without input from the pilot, the airplane rolled to the right, dipping its right wing. The pilot attempted to correct the attitude of the airplane by increasing left cyclic input, increasing the throttle, and applying full left rudder. Despite his efforts, the airplane continued to roll right and struck the ground. After impact the airplane spun around clockwise 180 degrees, coming to rest facing southeast. Approximately 3 gallons of fuel remained on board after the accident. A Federal Aviation Administration inspector interviewed the pilot after the accident. The pilot stated that he was flying low and in a circle when the right wing dropped excessively, and he was too low to recover. The airplane then impacted evergreen trees and came to a stop. The pilot reported he had accumulated 519 hours of total flight experience in the airplane.