On June 20, 2004, at 1830 central daylight time, a Cessna 401, N3234Q, piloted by a private pilot, was substantially damaged when it departed the runway pavement during a hard landing on runway 5 (6,498 feet by 150 feet, asphalt) at Mount Vernon Airport (MVN), Mount Vernon, Illinois. The personal flight was conducted under 14 CFR Part 91 without a flight plan. Visual meteorological conditions prevailed at the time of the accident. The pilot and passenger reported no injuries. The local flight departed MVN approximately 1700. A witness reported that the accident aircraft turned a "close-in" left base for the runway at a "high power setting." He recalled thinking that the pilot was going to execute a "low level, high speed pass." The aircraft did not appear to him to be in a normal landing descent profile. The aircraft crossed the runway threshold approximately 35 feet above ground level (agl) and the power was reduced to idle. The aircraft leveled about 30 feet agl and subsequently settled to 5-10 feet agl. As it approached the intersecting runway, the aircraft "dropped" and landed on all three landing gear. He noted that a "large cloud" of smoke rose from all three wheels. After a ground roll of about 100 feet, the aircraft slowly began to settle onto its left wing and he could hear the propeller begin to hit the ground. A Federal Aviation Administration inspector conducted an on-scene inspection. He reported that the aircraft landed approximately 500 feet prior to the intersecting runway. Tire marks on the pavement were consistent with the right main landing gear contacting the runway first, followed by the left main landing gear and nose gear, 15 feet later. Ground scars consistent with left engine propeller strikes were observed 25 feet after the point where the left main gear touched down. The aircraft subsequently departed the north side of the runway about 2,000 feet past the runway intersection, striking 2 runway lights in the process. The post-accident examination of the aircraft revealed that the left wing had been severed vertically through both the upper and lower skin, from the leading edge to the forward spar, consistent with impact to a runway light assembly. The left wing tip tank remained secured at the aft fitting. Forward-to-aft scrape marks were present on the left wing tip lower skin. The left main landing gear down lock linkage was fractured above the hinge. The fracture surface appeared consistent with an overload failure. The left-engine propeller blade tips were curled aft and exhibited scrape marks. According to the accident report submitted by the pilot, his most recent flight review was completed in July 1986. His most recent medical certificate was issued on May 11, 1999. The pilot did not include a narrative in his accident report. Weather conditions recorded by the MVN Automated Weather Observing System (AWOS) at 1755 were clear skies and winds from 020 degrees at 5 knots. At 1855, the AWOS recorded clear skies and calm winds.