On August 15, 2000, at approximately 1030 mountain daylight time, a Sukhoi SU-29, N55SU, was substantially damaged during a landing at Vance Brand Airport, Longmont, Colorado. The airline transport pilot, the sole occupant onboard, was not injured. The pilot/owner was operating the aircraft under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the local flight that originated approximately 30 minutes before the accident. The pilot had not filed a flight plan. The pilot said that the purpose of the flight was to practice aerobatic maneuvers. On his return to the airport, the landing was "uneventful, in fact remarkably smooth." The pilot said that shortly after touchdown, the airplane swerved to the right and exited the runway. He said that the left wing "slightly touched the grass." He continued to taxi to his hangar. Postaccident examination was delayed several months (until December 11, 2000) to allow Sukhoi representatives to assess the damage. They determined that several structural tubes just aft of the engine firewall needed to be replaced. The damaged area of tubing was where the main landing gear attached to the fuselage. It could not be determined if the structural damage that occurred on August 15, 2000, was the result of one landing or progressive damage from several landings. The tubes that needed replacement following the August 15, 2000, event had been previously damaged (bent or broken) during an accident on May 11, 1996. At that time, several unsuccessful attempts were made to acquire Russian materials and technical assistance. The decision was made to perform the repairs using American materials. According to the Sukhoi representatives, the American tubing and welding rods were "incompatible" with the original Russian materials.