Incident Overview
A Beech 1900 aircraft arrived at the gate and was chocked. A tug, pulling a baggage cart, was parked next to the left wing, facing the opposite direction, with its engine left running. The unoccupied tug then began moving on its own, executed a right turn of 270 degrees, and struck the left side of the airplane's nose landing gear. As the tug impacted the nose gear, the aircraft's tail pivoted to the left and struck a ramp worker, who fell to the ground and sustained a fractured elbow.
Driver Statements and Parking Brake Condition
When interviewed, the driver of the tug made conflicting statements regarding whether the parking brake was set or not set. The station manager reported that the tension on the parking brake handle was looser than normal. He was unable to determine if the parking brake had been set and then released on its own, or if it had not been set at all.
Operational Procedures
Drivers were taught to set the parking brake when exiting the vehicle, but there was no requirement to chock the tug or shut the engine off when the driver exited the vehicle.