On July 25, 1998, at 1757 central daylight time, a McDonnell Douglas MD-83, N9620D, sustained minor damage when it collided with an airport operations vehicle while taxing to the ramp after landing at the Lambert-Saint Louis International Airport (STL), Saint Louis, Missouri. The domestic flight was operating under the provisions of 14 CFR Part 121 as Trans World Airlines (TWA) flight 150, scheduled passenger service from Los Angeles International Airport, Los Angeles, California, to STL. The flight was operating on an Instrument Flight Rules flight plan. Visual meteorological conditions prevailed at the time of the incident. The two airline transport pilots, four flight attendants, and 142 passengers reported no injuries. One ground personnel individual sustained minor injuries. The aircraft turned right on taxiway "R" after landing on runway 12L (9,003 feet by 150 feet, grooved concrete), then made a right turn on taxiway "P", and a left turn on taxiway "N". According to an Air Traffic Control (ATC) clearance, the flight held short of runway 12R. After receiving a clearance to taxi across 12R, the aircraft was instructed to turn right on taxiway "A". A City of Saint Louis sweeper truck, truck 145, was performing maintenance on the field. While driving, the operator of the truck saw a piece of debris at the intersection of taxiways "A" and "T". According to a statement by the operator, "I pulled my sweeper to the grass area of the northside of shoulder off alfa taxi-way and I got out of the sweeper and walked to break off the object that were sticking up in the middle of the taxi-way (alfa) and (tango). I walked back to my sweeper and I looked over my left shoulder and glance aircraft wing strike the rear of sweeper, that's all I remember." According to statements made by the operator, after he parked the sweeper, he set it in neutral and set the parking brake. According to a statement made by the first officer of TWA flight 150, "While making the turn onto Alpha taxiway I heard [the captain] say that he saw a person on taxiway Alpha. When the person came into my view I noticed he was exiting to the right of the taxiway. I then saw him walk to a street sweeper, located partially on the grass, to the right of taxiway Alpha. I determined that the sweeper was located well clear of our aircrafts path, so clear that it did not deserve mentioning to [the captain]. As our aircraft passed abeam Tango taxiway I felt a minor bump which I thought to be a pothole...I received an inter phone call from the cabin...The flight attendant on the inter phone said that a passenger had seen the wing tip make contact with the street sweeper. At the same time I heard the TWA ramp tower tell us of damage to our right wing tip." "When we exited the cockpit a flight attendant and passenger told us that the right wing tip had knocked a person off of the street sweeper, and the person may be severely injured." According to the Airfield Administrator's report of the incident, the aircraft did not notify Air Traffic Control (ATC) of hitting the sweeper. Another aircraft, TWA flight 546, reported, "there was a man down on the north side of taxiway alfa" to ATC. ATC personnel contacted city operations with a request to check on the man down. In a statement by an operations worker, he received a radio call that the operator of truck 145 was not responding to radio calls. After hearing the position from TWA flight 546, he responded that he would investigate. Upon reaching the incident scene, he saw a person from operations tending to the sweeper operator. In a statement, the person tending to the sweeper operator stated that the sweeper operator "was on hands and knees swaying from side to side." The person tending to the operator called airport operations to request emergency vehicles. While the emergency vehicles were responding, an operations foreman and two other operations persons responded to the scene of the incident. Emergency vehicles responded and took the injured sweeper operator to the hospital. TWA personnel joined the operations personnel to assess the scene of the incident and to take photographs of the sweeper and the aircraft. The operator of the sweeper was released from the hospital later that evening with no reported injuries.