On February 13, 2004, at 1400 central standard time, an American Champion Aircraft 8GCBC, N186AC, piloted by a commercial pilot, sustained substantial damage when it impacted a ditch and subsequently nosed over while landing on a gravel road near Sunburg, Minnesota. Visual meteorological conditions prevailed at the time of the accident. The flight was operating under the provisions of 14 CFR Part 91 without a flight plan. The pilot was not injured. The flight departed at 0830 from a private airstrip near Castlewood, South Dakota. The pilot stated the purpose of the flight was to take aerial photographs of several Minnesota farms. The pilot reported that while in cruise flight he had the "sudden urge to use the bathroom" and he selected a nearby gravel road to land on. The pilot stated that during landing rollout he noticed a sign on the left side of the road. While he attempted to maneuver the airplane to avoid striking the sign, the right wheel "got sucked into the ditch which was full of snow." The airplane subsequently impacted the ditch and nosed over. The airplane was configured with extended range fuel system that increased the airplane's maximum endurance to approximately 7 hours. The accident flight was reported to be approximately 5 1/2 hours in duration.