On August 19, 2000, at 1600 eastern daylight time (edt), a Piper PA-28-235, N9174W, operated by a private pilot, sustained substantial damage during a hard landing on runway 8 (3,501 feet by 75 feet, dry asphalt) at the Mackinac Island Airport (MCD). Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under 14 CFR Part 91. No flight plan was on file. The pilot and passenger, on board the airplane, reported no injuries. The cross-country flight originated at Jackson, Michigan, and was en route to Mackinac Island, Michigan. In his written statement, the pilot said his flight was uneventful until the final approach to landing. He said that the airport winds were reported as 3-4 knots from the north. "Over the threshold, the left wing [of the airplane] went up to approximately 35-40 degrees." The pilot said that he was able to "stabilize the aircraft just prior to touchdown. The initial landing was hard, and the plane porpoised prior to the second touchdown." The pilot said the airplane then veered to the left. "The plane continued on to the grassy area on the left side of the runway and the nose gear collapsed." Following the accident, the pilot said he observed a large American flag, located near the tree line south of the runway, "standing straight out (north to south)." The pilot said the airport manager told him that the north winds come over the top of the trees, descend to the ground, start swirling, and continue south across the runway. A Federal Aviation Administration inspector examined the airplane at the Mackinac Island Airport. The propeller showed torsional bending, chordwise scratches, tip curling, and several nicks in the leading and trailing edges of the blades. The nose gear was broken aft. The firewall was bent rearward. Several of the bottom fuselage rails were bent inward. One of the rails was punctured inward. Flight control continuity was confirmed. An examination of the engine and other airplane systems revealed no anomalies. At 1551 edt, the automated weather observation system (AWOS) at the Mackinac Island Airport, reported clear skies, 10 miles visibility, winds 360 degrees at 6 knots, temperature 65 degrees F, dew point 35 degrees F, and altimeter 30.27 inches of Mercury. At 1554 edt, the automated surface observation system (ASOS) at Alpina, Michigan, 66 miles from MCD at 140 degrees, reported clear skies, 10 miles visibility, winds 320 degrees at 11 knots, gusts to 18 knots, temperature 65 degrees F, dew point 37 degrees F, and altimeter 30.26 inches of Mercury. The Airport/Facilities Directory, East Central U.S. for the Mackinac Island Airport, states in the communications/navigation aids remarks section, AWOS-3 winds unreliable due to trees north of the runway.