On July 30, 2004, about 1900 central daylight time, an experimental amateur-built Tjerrild Rotorway Exec helicopter, operated by a private pilot, sustained substantial damage on impact with terrain and crops during a forced landing, following an in-flight loss of engine power near Eureka, Illinois. The personal flight was operating under 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the accident. No Flight plan was on file. The pilot and passenger were uninjured. The local flight originated near Eureka, Illinois, and was in cruise flight at the time of the loss of engine power. The pilot stated: Took off from Eureka College ball field toward the South. Executed climbing left hand turn around to a heading of [approximately] 360 [degrees] and up to 1000 MSL [feet above mean sea level]. Established level cruise at 1000 MSL and 70 mph. Engine stopped without warning. Executed an auto rotate into corn field below. As main rotors entered corn the aircraft yawed left and stopped partially tipped over on left side. No injuries. Accident site [approximately] 1 mile from take-off point. A Federal Aviation Administration Inspector performed an inspection of the wreckage. The high-tension wire from the ignition coil was found detached. Rotorway International issued a service bulletin dated May 15, 1992 on the helicopter's ignition system. That service bulletin stated: TO ALL EXEC BUILDERS EXEC MANDATORY/ADVISORY SERVICE BULLETIN A-07 History: Electronic Ignition Systems have proven to be more reliable and easier to maintain than conventional distributor ignitions. Action: For Exec helicopters, RotorWay International recommends ONLY the Dual electronic Ignition system as equipped on our R.I. 162 engines. This system features two completely independent ignition systems, including two spark plugs per cylinder, designed to operate simultaneously. Either ignition system will support full power performance. We recommend only this ignition system and will no longer sell or support distributor ignitions. The dual electronic ignition system may be fitted to any Exec with the RW 145 or RW 152 engine, and is strongly recommended. If you have purchased a rebuilt distributor from RotorWay International, the conversion to the dual electronic ignition system is regarded as mandatory. The accident helicopter was not modified with that service bulletin.