On July 21, 2001, about 1415 eastern daylight time, a Piper PA-28-181, N17AV, was substantially damaged during an overrun at Mattituck Airbase (21N), Mattituck, New York. The certificated private pilot and three passengers were not injured. Visual meteorological conditions prevailed at the time of the accident. No flight plan had been filed for the flight, between Igor I. Sikorsky Memorial Airport (BDR), Bridgeport, Connecticut, and Mattituck. The personal flight was conducted under 14 CFR Part 91. According to the pilot, while approaching the airport, he observed a Mooney on a 4-mile final to runway 01. He followed the Mooney, but when he was on final, saw that it had not yet cleared the runway, and executed a go-around. At the time, the windsock indicated that the winds were from the west-northwest. The pilot completed the next approach, and the airplane touched down, with full flaps, 200-300 feet from the runway threshold. The pilot felt that the touchdown speed was faster than he was accustomed to, but felt an aborted landing would have been too dangerous, since there were trees at the end of the runway. The pilot attempted to stop the airplane on the runway; however, the braking was limited. The airplane approached the departure end of the runway at an estimated 10-15 mph. It then rolled off the end of the runway and struck trees. The pilot felt that during the approach, the wind had shifted to a "significant" tailwind. According to a Federal Aviation Administration (FAA) inspector, witnesses reported that the airplane landed about halfway down the runway at a high rate of speed. The FAA inspector also noted that wind indications could be different at each end of the runway. Runway 01 was 2,200 feet in length, and 130 feet in width, with trees at the northern end. According to the PA-28-181 Pilot's Operating Handbook, the landing roll at sea level pressure, 25 degrees Centigrade, a gross weight of 2,500 pounds, full flaps, full-stall touchdown, and a zero-wind condition should have been approximately 950 feet. A 5-knot tailwind (the maximum for which data was provided) should have required about 1,280 feet. Winds, recorded at an airport about 10 nautical miles to the southwest at the approximate time of the accident, were from 200 degrees true, at 9 knots. The temperature was 24 degrees Centigrade.