Boeing 737-3H4 N624SW accident near Los Angeles, California

Probable cause

The tug operator’s failure to comply with company procedures when parking an unoccupied baggage tug, and the failure of the tug’s seat switch to disengage the electric motor when weight was removed from the driver’s seat.

NTSB analysis

While the airplane was being pushed back for its flight, it was struck by a runaway baggage tug. The tug operator reported that he stopped on the ramp to pick up two bags. He exited the tug without setting its parking brake, turning off its engine, or placing the gear selector in neutral or park, which was not in accordance with the tug company’s ground equipment general driving rules. The tug operator then placed the first bag on the passenger seat, which company procedures caution against doing. While the tug operator was handling the second bag, the unoccupied tug began to move because the first bag had fallen off the passenger seat onto the accelerator pedal. The tug moved forward, struck a hydrant fueling cart on the ramp, and then veered toward the left side of the airplane. The tug impacted both of the airplane’s engines and its fuselage. If the tug operator had followed company driving rules, the accident could have been prevented. In addition, postaccident examination of the tug revealed that the electrical motor disengaging seat switch, which is designed to disengage the tug's electrical motor when weight is removed from the driver's seat, was inoperative; therefore, it did not prevent the tug from moving forward as designed.

Text from the NTSB. Open the NTSB docket for WPR10FA199 for the full record.