On May 21, 2000, at 1150 central daylight time, a Piper PA-31T1 twin-engine airplane, N301TA, was substantially damaged when it taxied into a parked airplane on the ramp at the William P. Hobby Airport near Houston, Texas. The private pilot and the two passengers were not injured. The aircraft was owned by TAR Air Corporation, of Bedford, Massachusetts, and was leased to the pilot. Visual meteorological conditions prevailed, and an IFR flight plan was filed for the 14 Code of Federal Regulations Part 91 personal flight. The proposed destination for the cross-country flight was Lufkin, Texas. According to the 2,600-hour pilot, the parking brake was set, the left engine was running, and he was starting the right engine. After the right engine started, the pilot checked the engine instruments. The pilot was unaware that the airplane was moving forward on the ramp. According to witness statements, the airplane traveled approximately 75 feet, and the right engine impacted the propeller of a parked, unoccupied Beech Bonanza single-engine airplane, N9968P. According to the pilot and the FAA inspector, who examined the airplane, the parking brake was not completely engaged. The right engine's outboard lower mount was pulled from the firewall and the left side of the firewall was buckled.