On June 18, 1994, about 0528 eastern daylight time, a Mooney M20C, N6679U, operated by the owner/pilot, impacted trees in Leesburg, Virginia, during an instrument approach. The airplane was substantially damaged. The private pilot, the sole occupant, was not injured. Instrument meteorological conditions prevailed and a flight plan was filed. The personal flight departed from Birmingham, Alabama, and was conducted under 14 CFR 91. The pilot stated that he began the flight about 1930 on the evening prior to the accident from Houston, Texas. He flew from Houston to Birmingham, Alabama. After refueling the airplane and obtaining a weather briefing, the pilot departed Birmingham at 0040 on the morning of the accident. As he approached the Leesburg Airport, the pilot obtained weather information from the Dulles International Airport Automated Terminal Information Service (ATIS), Washington, D.C. The pilot recalled that ATIS was reporting a ceiling of 1,100 feet above the ground (agl) and a partially obscured sky. The actual recorded ATIS six minutes after the accident reported a cloud ceiling of 700 feet agl, a partially obscured sky, and a visibility of 1/2 mile in fog. The pilot was vectored for the localizer approach to runway 17 at the Leesburg Airport by air traffic control (ATC). The distance measuring equipment (DME) was out of service at the time of the approach, and the pilot stated that he was aware of the outage from his original weather briefing in Houston prior to the flight. The published minimum descent altitude (MDA) and visibility for the approach (approach plate attached) without the use of DME is 1,020 feet mean sea level (636 feet agl) and one mile. The pilot began the approach and impacted trees. In a telephone interview one day after the accident, the pilot stated that after passing the middle marker, he "... went down too fast..." through the MDA after "... missing a step down fix." He then saw the tops of trees below him, and the right wing and right landing gear contacted the trees. In a written statement to the NTSB, the pilot further stated that he "...either reached the [1,000-foot] MDA prior to the 2.7 mile DME fix which put me in the trees or I descended below the MDA." Following the impact with the trees, the pilot "pulled up" and was able to perform a missed approach. He elected to keep the landing gear extended and declared an emergency with ATC at the Dulles International Airport. He then performed the instrument landing system (ILS) approach to runway 1R at Dulles and landed uneventfully. He did not report any malfunctions with the airplane during the flight. According to an FAA aviation safety inspector from Washington, D.C., the right wing, right landing gear, and left elevator sustained substantial damage. The pilot told the FAA inspector that he had been awake for about 24 hours prior to the accident, except for a 2 1/2 hour "nap" in his automobile. In a written statement to the NTSB, the pilot stated: "My judgement may have been adversely impacted by the fact that I didn't get a full days rest prior to the overnight flight."