On June 29, 2002, at 1630 eastern daylight time, a 1929 Waco ASO, NC763E, was substantially damaged during an emergency landing at the Knox County Airport (4I3), Mt. Vernon, Ohio. The airline transport pilot and a passenger were not injured, and one passenger sustained minor injuries. No flight plan was filed for the flight that originated at the Wynkoop Airport (6G4), Mt. Vernon, Ohio, at 1600. Visual meteorological conditions prevailed for the personal flight conducted under 14 CFR Part 91. In a written statement, the pilot stated that after he departed Wynkoop Airport, he saw several people on the runway frantically waving at him. The pilot knew something was wrong, and realized the left main landing gear strut had broken during takeoff. He then flew to Knox County Airport, which had a longer and wider runway. After touchdown, the airplane skidded on the broken landing gear, then flipped over onto its back. A Federal Aviation Administration (FAA) inspector performed an on-scene examination of the airplane. According to the inspector, the wing carry-through spar was cracked and the left landing gear strut fitting was separated at the point where it attached to the fuselage. The inspector also said that there had not been any recent maintenance or welding performed on the fitting. The Safety Board's Materials Laboratory performed an examination of the left fuselage-fitting eyelet. Visual observation of the fractured surface showed four distinctive regions that were flat, smooth, and dark in color, properties consistent with pre-existing fatigue cracking. Macroscopically, all four regions showed distinct demarcation lines at the edges of the darker area. Two of the fatigue regions originated on the outer surface of the upper washer and propagated partially through the thickness of the washer. Both fatigue regions showed numerous ratchet marks, consistent with multiple origins of initiation. They were located on the outer edges of the fractured region near the weld beads. Both of the regions appeared highly oxidized and were large in area. One of the regions had numerous ratchet marks, while the other one had a very defined single initiation site, and both dark and light fatigue areas. The airframe had accrued a total of 1,440 hours at the time of the accident. The pilot reported a total of 12,350 flight hours, of which, 180 hours were in make and model. Weather at the Port Columbus International Airport (CMH), Columbus, Ohio, at 1651, included winds from 110 degrees at 6 knots, visibility 7 statute miles, few clouds at 6,000 feet, and broken clouds at 20,000 feet.