On June 17, 1996, about 1850 eastern daylight time, a Cessna 150M, N47ES, registered to ISO Aero Service Inc., operated by Raleigh East Aviation, as a 14 CFR Part 91 instructional flight, experienced a total loss of engine power while performing a simulated engine failure. A forced landing was made to a tobacco field, and the airplane nosed over on touchdown. Visual meteorological conditions prevailed and no flight plan was filed. The certified flight instructor and student pilot reported no injuries. The airplane sustained substantial damage. The flight originated from Raleigh East Airport about 30 minutes before the accident. The certified flight instructor (CFI) stated he informed the student pilot to start a power off descending glide from 3,000 feet to 2,500 feet. The student pilot did not turn the carburetor heat on. The student pilot leveled off at 2,500 feet. The CFI gave the student pilot a simulated engine failure. The student pilot performed his emergency procedures, assumed the best rate of glide airspeed, turned towards his forced landing area, and over shot the forced landing area. The CFI took control of the airplane and increased power. The engine would not produce full power and quit. The CFI made a forced landing to the tobacco field, and the airplane nosed over on touchdown. Examination of the engine assembly and accessories was conducted by the head mechanic of ISO Aero Service Inc., in the presence of the FAA and Raleigh East Aviation personnel. No evidence of a precrash mechanical failure or malfunction of the engine was found. Review of the probability carburetor icing chart revealed that the engine would encounter serious icing at glide power based on the weather conditions at the time of the accident.