On February 18, 1994, at 1000 central standard time, an unregistered Argo Minimax, experimental airplane, collided with the ground, after the pilot experienced a reported flight control problem, near Franklin, Tennessee. The personal flight operated under 14 CFR Part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The airplane sustained substantial damage, and the non-rated pilot received serious injuries. The flight departed Spring Hill, Tennessee, at 0815 hours. According to the student pilot, while maneuvering, the flight controls jammed, and the controllability of the airplane became limited. A visual check of the exposed flight control surfaces and cables failed to reveal a mechanical problem. The pilot selected a field and established an emergency descent. Once the airplane was within the landing area, the pilot deployed the recovery parachute. The airplane descended to the ground in a nose low attitude. According to the student pilot, prior to his takeoff, he placed a communication radio battery on the floor of the airplane; the pilot believed that the battery pack jammed the flight control. According to the pilot, the aircraft originally was configured for one five gallon fuel tank. He modified the airframe for the installation of two five gallons tanks, one in each wing assembly. A review of 14 CFR Part 103 disclosed that ultralight vehicles are limited to a total of five gallons of fuel capacity.