On November 2, 2001, about 1756 central standard time, a Piper PA-28R-201T, N5984V, piloted by a commercial pilot, sustained substantial damage on impact with terrain and an object following a gear collapse during landing roll on runway 35 (3,600 feet by 60 feet, dry/asphalt) at Mount Hawley Auxiliary Airport (3MY), near Peoria, Illinois. The airplane exited the runway, impacted a runway light, and came to rest off the runway's right side. The personal flight was operating under 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the accident. The pilot was uninjured. The flight had filed and had activated an IFR flight plan. The flight had departed from Naper Aero Club Airport, near Naperville, Illinois, about 1710, had cancelled the IFR flight plan while approaching 3MY, and was landing at 3MY at the time of the accident. The pilot reported: As I turned from base to final, I again ordered a pre-landing checklist noting that the gear was showing 3 green lights on the panel. The initial phase of the landing and touch down seemed normal but after a short period (I cannot define how need) as the aircraft proceeded down the centerline, I noticed the right side of the aircraft descending as though the right gear was collapsing and the right wing descending toward the pavement. I cannot say with certainty what corrective action I took but the aircraft's right wing continued to descend. Before the wing came in contact with the ground, I was unable to steer the aircraft. The aircraft began dropping from the nose as the aircraft turned to the right. The propeller struck the asphalt just prior to the aircraft departure from the runway. After exiting the runway the aircraft continued to turn approximately 120 degrees from the initial landing direction and come to a stop between the runway and taxiway. A mechanic at 3MY stated: ... The aircraft was in the grass between runway 35 and the taxiway. It was about 2700 feet from the approach end and about 50 feet to the east in the grass. Peoria Approach was notified. On Saturday morning (11/3/01) we removed the aircraft from the grass. When lifted the Right wing the gear fell down and locked. I jacked the left wing to engage the lock, the left gear was down but, was not locked. The nose gear would not fall down due to the gear doors were bent, so I used the hydraulic pump to push it down and it locked. We hooked our tug to the aircraft and put it in a tie down. Federal Aviation Administration Inspectors examined the airplane. The inspectors found that the airplane landed long on runway 35 and touched down on the left side of the centerline. (See appended photographs) An inspector stated: Photographs indicate that the aircraft immediately began a hard right turn. Shortly before exiting the runway, skid marks show that the right main landing gear started to fold up. The aircraft came to rest on the east side of the runway with the nose and right main gear retracted. One runway light was broken off after it was struck with the left wing.