On July 3, 1996, approximately 1155 mountain daylight time, N51763, an Enstrom 280C, was substantially damaged during a forced landing 8 miles south of Castle Rock, Colorado. The flight instructor and the private pilot receiving instruction were not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The instructional flight was being conducted under Title 14 CFR Part 91. The flight originated at Englewood, Colorado, on July 3, 1996, approximately 1150. According to the pilots, they were in a slow climb from 500 feet to 750 feet agl (above ground level). The engine began to sputter, then lost power. They made an autorotation and run-on landing on a rough field. During the landing roll, the left front skid and crossover tube collapsed, causing the helicopter to veer 90 degrees to the left and the main rotor blades to sever the tail boom. An FAA airworthiness inspector examined the helicopter on November 20, 1996. According to his report, the magneto (Bendix m/n D4LN-2200, s/n 35413) had failed. When the magneto was rotated, none of the 12 leads produced a spark. When the distributor cap was removed, it was noted that none of the points opened when the magneto was rotated. In a telephone interview, the inspector also said that on the day prior to the accident, he observed the helicopter landing at Centennial Airport, Englewood, Colorado. He said the engine was missing noticeably. He suggested that the pilots (the same ones involved in the accident) have the engine checked before further flight. According to the inspector, the instructor replied that the condition was "common on Enstrom helicopters when the engine is hot."