B737 Undifferentiated or Other Model
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Aircraft Aircraft Damaged; General Maintenance Action
Human Factors
I was pushing aircraft off of gate for departure. Seconds after commencing pushback a van drove behind the left wing of the aircraft. When I lost sight of the van behind engine one and my wing walker on the left wing dropped his wand from the all clear signal to the stop signal I stopped my push tractor. When I pushed the brake pedal; the brakes grabbed and stopped very abruptly (a common issue with this model of push tractor). The abrupt stop caused the shear pin on the towbar to break. I informed the flight deck of the events via interphone and they responded that the parking brake was set and that they were calling maintenance for inspection per policy. When the maintenance technician arrived; he found a broken taxi lens light. The AMT spoke English with an accent that was very difficult to understand; and I was unable to act as a relay between him and the flight deck on the interphone. When maintenance management and Area Manager (AM) arrived on scene; the AMTs began removing the taxi light for replacement. The AM asked twice whether the towbar made contact with the taxi light. I responded that I did not see it make contact and would be very surprised if it was in fact the cause of the lens chip. To further complicate matters; the AMT with the difficult accent dropped the light assembly when it was detached from the aircraft; making further inspection impossible. AM and maintenance management conferred and deemed me responsible for breaking the lens; making the incident a near miss. I was immediately sent for drug and alcohol testing; which were both negative; and to write a statement with a shop steward. I feel that the classification of this incident as a near miss was the result of the AM and maintenance management's collaboration to avoid being charged with the damage that was likely missed on an arrival or departure walk around.
A tug driver reports stopping a pushback abruptly (grabby brakes) when a truck drives behind the aircraft and the wing walker signals stop. The abrupt stop caused the shear pin on the towbar to break and maintenance is called.