On August 19, 2012, about 1245 central daylight time, an experimental amateur-built Jones Kitfox III, N942EJ, impacted terrain following a loss of engine power after takeoff from Cottonwood Airport, Rockford, Illinois. The pilot performed a forced landing to a field after the airplane experienced a loss of engine power. The private pilot and a passenger were uninjured. The airplane sustained substantial damage to the fuselage, wing, and stabilizer. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and a flight plan had not been filed for the local flight that was originating at the time of the accident. The pilot stated that the airplane experienced a loss of engine power after takeoff while at 300 feet above ground level. The pilot then performed a forced landing to a bean field. The pilot stated that a spark plug had loosened after he replaced it about 2 hours of time in service before the accident flight. The pilot's safety recommendation was to tighten and then recheck spark plugs when they are installed.