NTSB Identification: CHI05LA179.
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Accident occurred Friday, July 08, 2005 in Chicago, IL
Probable Cause Approval Date: 01/31/2007
Aircraft: Boeing 737-7H4, registration: N494WN
Injuries: 110 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The scheduled domestic passenger flight sustained substantial damage when the airplane impacted a food service truck during the flight's pushback. The food service truck tipped on its side after the impact. The operator stated that an additional provisioning (provo) truck was parked behind the aircraft so that the additional driver could assist the driver of the assigned provisioning truck. The captain was informed by the pushback driver of the "provo truck" at the rear galley and the captain told the driver to push at his discretion. The assigned truck servicing the flight completed its service and was marshaled back from the aircraft and departed. The pushback driver, unaware of the second truck behind the aircraft, began to push the aircraft out. During pushback, as the flight crew initiated engine start, the APU stopped running, the engine start was terminated, and the push sequence was stopped. The pushback driver stated that he experienced "difficulty with going forward" and stopped the push. The pushback driver stated that he "did not see anyone telling me to stop pushing that my zone was not clear." The wing walker took his position at the taxiway to walk out the flight and was aware of the truck behind the aircraft. The wing walker stated that "I put up the stop signal and yelled stop but the plane kept on being pushed." The operator's ground operations manual stated that the pushback driver "is ultimately responsible for ensuring that the aircraft has been secured, all personnel involved in the push are in proper position, and the pushback is conducted in a safe manner." The manual did not list, note, caution, or warn the pushback driver to stop the pushback when the driver's visual contact with the guide agent (wing walker) is not maintained. The manual told the guide agent to "always be in visual range of the pushback driver ... ." The operator was asked if there was a back up aural signal to the visual stop signals. The operator indicated that there was none and "since this event we are testing headset communication systems." When asked where the supervisor was, the operator responded that "the supervisor was within visual range but his attempts to stop the push were not heard or seen."

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The pushback tow driver not maintaining visual lookout for the wing walker's visual signal, and the driver not maintaining clearance from the vehicle during the pushback for taxi. Factors to the accident were the standing vehicle behind the airplane, the inadequate group/crew coordination for the pushback, and the lack of guidance in the company's manuals to stop the tow when visual lookout is not maintained.

Full narrative available

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