On July 8, 1994, at 0815 central daylight time, a Cessna 150, N9284U, sustained substantial damage following a loss of engine power and subsequent off-airport forced landing near Andover, Minnesota. The certificated flight instructor and private pilot aboard reported no injuries. The 14 CFR Part 91 instructional flight originated in Anoka, Minnesota, at 0800. No flight plan was filed, and visual meteorological conditions prevailed at the time. According to the instructor's statement, he reduced the engine power to simulate a rough running engine, and than pulled the mixture control out to simulate an engine failure. He said the private pilot did an excellent job of remedial emergency procedures, including pulling the carburetor heat "on" promptly. The instructor wrote that he was satisfied with the private pilot's actions, and told him to restore power. When the private pilot pushed the mixture in to full rich, the engine would not restart. The instructor took control of the airplane and made a forced landing on a nearby field. He was unable to stop the airplane prior to colliding with obstructions. The reported surface temperature in the area at the time of the accident was 61 degrees and the dew point was 59 degrees. The attached Carburetor Icing Probability Chart places this temperature and dewpoint combination in the severe icing category. Postaccident inspection of the airplane and its systems discovered no preimpact mechanical anomalies. The engine was started and run at the site with no observed mechanical deficiencies.