On October 15, 2001, about 0855 eastern daylight time, a Cessna 172P, N52685, registered to Marashi Aviation, LLC., operating as a Title 14 CFR Part 91 personal flight, sustained a ground collision with airport terminal concrete columns at Knoxville's McGhee Tyson Airport, Tennessee. Visual meteorological conditions prevailed and an instrument flight plan was filed. The aircraft received substantial damage, and the commercially-rated pilot and a passenger were not injured. The planned departure had not occurred at the time of the accident. According to the pilot, after engine start and attempt to taxi, he realized that a chock was still in place at his right main wheel. He set the parking brake, told his right seat occupant to sit still, and exited the cockpit to remove the chock. Once he removed the chock, the aircraft taxied forward where the right wing collided with a concrete column of the terminal canopy, pivoting the aircraft and causing the left wing to collide with another column. The wing main spar sustained damage, as well as left wing fuel tank rupture. Postcrash examination of the cockpit revealed that the parking brake was not set. He stated that the parking brake must have been inadvertently released as he slid out of his seat. According to an FAA inspector, the distance the unpiloted aircraft traveled prior to the collision with the concrete columns was about 300 feet. The ramp possessed a slight downhill slope in the direction the aircraft was headed at engine start, and although the pilot tried to catch the taxiing aircraft, he was unable. The left wing sustained leading edge collision damage one foot from the wing tip, the right wing leading edge sustained damage just outboard of the lift strut attachment, and the wing spar center section was bent. The passenger exited the aircraft, postcrash, uninjured. Two FAA inspectors examined the brake system and found no discrepancies. Their conclusion was, "It is my opinion that the pilot accidentally hit the parking brake handle with his knee when he exited the aircraft and the return spring for the handle pulled the parking brake handle to the off position, releasing the brakes."