PORTLAND, OR, USA
N291AS
BOEING 727-290
THE BOEING 727 WAS PUSHED BACK FM THE GATE COUNTERCLOCKWISE THROUGH AN ARC OF 90 DEGREES RESULTING IN MISPOSITIONING THE ACFT RELATIVE TO THE INTENDED TAXI DIRECTION. THE GROUND CREW (TUG AND SAFETY OPERATORS) ATTEMPTED TO RESOLVE THE OUT OF POSITION CONDITION BY CONTINUING THE PUSH BACK THROUGH A SECOND 90 DEGREE (COUNTERCLOCKWISE) ARC. THIS REQUIRED PUSHING THE AIRCRAFT UPSLOPE ACROSS THE RAMP. DURING THE SECOND 90 DEGREE ARC THE TUG BECAME POSITIONED APPROXIMATELY 90 DEGREES TO THE TOWBAR/AIRCRAFT LONGITUDINAL AXIS. THE DOWNSLOPE AND IDLE POWER CONDITIONS OVERPOWERED THE TUG'S BRAKING CAPACITY AND THE TOW BAR BROKE UNDER A BENDING LOAD ALLOWING THE AIRCRAFT TO ROLL FORWARD IMPACTING THE TUG. ALL THREE B-727 ENGINES WERE OPERATING AT IDLE THRUST.
Source: NTSB Aviation Accident Database
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