On February 16, 2003, about 1430 eastern standard time, a Cessna 140, N76897, was substantially damaged during a forced landing to a field near Fryeburg, Maine. The certified flight instructor (CFI) and the private pilot were not injured. Visual meteorological conditions prevailed for the flight that departed Eastern Slopes Regional Airport (IZG), Fryeburg, Maine, about 1400. No flight plan was filed for the local instructional flight conducted under 14 CFR Part 91. The private pilot stated that he had recently purchased the airplane, and was receiving flight instruction. The private pilot completed some maneuvers at an altitude of 2,500-3,000 feet msl, and about 1430, the CFI applied carburetor heat while setting the engine power to idle for a simulated engine failure. The private pilot completed the emergency checklist items, and positioned the airplane for a simulated forced landing to a field. During the descent, the carburetor heat remained on, and the CFI occasionally cycled the throttle to "clear the engine." About 15-20 feet above the field, the pilot attempted to add power for a go-around, but the engine did not respond. The CFI then took control of the airplane, and performed a forced landing to the field. During the landing, the airplane struck a snow bank and came to rest inverted. The airplane sustained damage to the gearbox, fuselage, wings, and vertical stabilizer. A certificated mechanic examined the wreckage after the accident. The mechanic was able to rotate the propeller by hand, and did not note any discrepancies with the engine. He also observed fuel in the airplane. The mechanic further stated that he believed the power loss occurred due to carburetor ice. He added that on the make and model accident engine, the carburetor was situated below the engine, and more susceptible to carburetor ice. In addition, the carburetor heat relied on two cylinders, rather than all four. The mechanic was confident that carburetor ice caused the power loss, and did not attempt to disassemble the carburetor to look for ice. A Federal Aviation Administration inspector stated that she did not examine the wreckage, but the certificated mechanic had determined the power loss was due to carburetor ice. The reported temperature at an airport approximately 30 miles southeast of the accident site, at 1451, was 16 degrees F. The reported dew point was -16 degrees F, which yielded a relative humidity of 22 percent. According to DOT/FAA/CT-82/44 Publication, Carburetor Icing Probability Chart, the engine was not susceptible to carburetor ice under those conditions.