On January 31, 1999, at 1630 mountain standard time, a Champion 7GCAA, N9668S, operated by a commercial pilot, sustained substantial damage during landing roll near Alliance, NE. The personal flight was operated under 14 CFR Part 91. There was no flight plan on file. Visual meteorological conditions prevailed at the time of the accident. The pilot reported no injuries. The flight originated from Alliance Municipal Airport, at time 1615, for a local flight. According to the pilot's written statement, the pilot flew over a friend's house and decided to land in a field adjacent to the house. The pilot stated that upon landing, on the plowed farm field, he, "... proceeded to get on the brakes and there was just no grabbing between the tires and the dirt field." The pilot stated that he applied more brakes, and, "... all of the sudden, the tail came up and the airplane nosed over and flipped onto its back." In a telephone interview with the pilot, the pilot stated that the landing was made to the north. Post accident investigation showed that there was substantial damage to three wing ribs, two wing struts, and the vertical stabilizer. A functional test of the brake system was conducted and no abnormalities were found. No other abnormalities were found with the accident airplane. Weather reports for the area reported winds from 150 degrees at 8 knots.