The student had about 75 hours experience in ultralight aircraft, and was undergoing a training programme to enable him to become an instructor. At about 100 feet above the ground after takeoff, the instructor closed the throttle to simulate an engine failure. The student was slow to react, and the airspeed rapidly decayed. The instructor took control and applied full power, but was unable to prevent the aircraft from contacting the ground heavily. This contact resulted in the lower fuselage striking the ground, and the throttle control became jammed. The aircraft became airborne again with full power applied, and the instructor turned off the ignition system. A second heavy touchdown occurred before the aircraft came to rest.