On June 13, 2004, at approximately 1230 mountain daylight time, a Northwing WS2, an unregistered ultralight, was destroyed when it impacted a cornfield adjacent to Yankee Field, an ultralight airstrip 5 miles northeast of Fort Collins, Colorado. The non-certificated pilot was seriously injured. Visual meteorological conditions prevailed. No flight plan had been filed for the local flight that was being conducted under the provisions of Title 14 CFR Part 91. The flight was originating at the time of the accident. The pilot reported he had just departed runway 18 and was approximately 100 feet agl when the engine lost power. He attempted to return to the field and landed "perpendicular [to the] grass strip." During the landing roll, the ultralight struck a berm, became airborne, and settled into an adjacent cornfield. The ultralight was destroyed and the pilot broke his right arm. The pilot reported possible fuel problems for the loss of power.