NTSB Identification: CHI01FA129.
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Scheduled 14 CFR NORTHWEST AIRLINES INC
Accident occurred Tuesday, May 01, 2001 in Minneapolis, MN
Probable Cause Approval Date: 07/02/2002
Aircraft: Douglas DC-9-31, registration: N9333
Injuries: 2 Minor,42 Uninjured.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The airplane was substantially damaged when it was struck by an aircraft tug during passenger boarding. The aircraft was parked and was being prepared for departure. The driver of the tug was moving the vehicle into position in order to connect the aircraft tow bar in preparation for pushback. He said that when he placed the tug into gear, it lurched forward into the parked aircraft. He said that pieces of the aircraft protruded through the windshield of the vehicle and pinned him into his seat. He said that he was unable to shift the vehicle into reverse and his leg was pinned on the accelerator pedal. Other ground workers in the area attempted to shut off the tug's engine. The driver said that the vehicle continued to drive forward until the engine was finally shut off. During the event, the pilot of the aircraft had applied the brakes when he noticed the unplanned movement of the airplane. The aircraft was pushed backward about 30 feet causing damage to the nose section of the fuselage. Subsequent to the accident, the tug was placed on jacks and a check performed. During the check it was found that the normal engine shutoff switch would not shut the engine off if the engine was operated at high throttle settings. It was further discovered that at high throttle settings, the brake system was not able to stop the rotation of the drive wheels. No anomalies were found during this test that would explain the lurching described by the tug driver. The tug had been involved in a previous incident where an aircraft was damaged. A report of the previous incident showed that the tug lurched when the driver was attempting to move the tug into position to connect to the aircraft. The tug manufacturer does not have records of operational problems associated with that model tug. The manufacturer also said that they were not aware of a history of lurching problems concerning the model tug in question. It was found that the distance from the cab of the tug to the nose of a DC-9 aircraft when the tow bar is attached is 4 feet 2 inches.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The partial failure of the aircraft tug for undetermined reasons. Full narrative available
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