On May 3, 1995, at 0735 mountain standard time, a homebuilt Godkey Kitfox IV, N4357Q, sustained substantial damage during a forced landing at Phoenix, Arizona. The aircraft was owned and operated by the student pilot and was on a local instructional flight. Visual meteorological conditions prevailed and no flight plan was filed. Neither the certificated flight instructor nor the student were injured. The flight originated from the Phoenix-Deer Valley Municipal Airport at 0730 on the day of the accident. The tower operator had just cleared the aircraft for takeoff from runway 25L when she heard the pilot declare an emergency. Looking in the direction of departure, she saw the aircraft complete a 180-degree turn back toward the runway. As she continued watching, the aircraft landed short of the airport boundary and struck the perimeter fence. The instructor reported that the aircraft had just taken off on runway 25L when the student, who was on the controls, informed him that the engine tachometer was not indicating full power. Just as he made the statement, the engine quit. He attempted a left 180-degree turn back toward the departure runway but did not have sufficient altitude to reach the runway and was forced to land short. A postaccident inspection by an Federal Aviation Administration (FAA) airworthiness inspector revealed that the ignition system was inoperative due to a defective diode. Spark plugs were inspected for serviceability and wiring was checked for continuity.