What happened
During routine pushback operations from the gate, the ground crew encountered difficulties due to adverse environmental conditions. The ramp surface was wet, and lighting conditions were poor, creating a dark environment for the ground crew. As the tug operator attempted to stop the airplane on the ramp, the vehicle slid to the left while the airplane moved to the right for undetermined reasons.
The mechanical failure occurred when the shear pin on the tow bar broke. This failure caused the airplane to turn sharply to the right. Following this incident, the tug driver jumped from the tug for safety. The tug then collided with the right side of the fuselage. Examination of the airplane revealed 9 damaged ribs on the bottom side of the fuselage.
The investigation
A physical examination of the aircraft was conducted to assess the extent of the damage. Investigators found that the shear pin on the tow bar had broken, which contributed to the loss of control during the pushback. The collision between the tug and the airplane resulted in structural damage to the lower fuselage area.
Findings
Contributing factors included the wet ramp surface and dark lighting conditions. The mechanical failure of the shear pin on the tow bar was a critical element in the sequence of events. The tug operator's attempt to stop the airplane on the ramp led to the sliding motion that preceded the collision.