An Air Carrier Captain and a tug river reported the towbar broke during a tow in to the gate. The aircraft rolled backwards prior to flight crew setting brakes.
Synopsis
An Air Carrier Captain and a tug river reported the towbar broke during a tow in to the gate. The aircraft rolled backwards prior to flight crew setting brakes.
Narrative
During the flight; we noticed we were scheduled to park at Gate X; which is a tow in gate for wide body aircraft in ZZZ. We briefed the Flight Attendants (F/As) accordingly and reviewed the Tow In checklist during the descent and approach briefing. After an uneventful landing and subsequent taxi in; we had to hold short of the Tow In lead in line while we awaited the ground crew to setup and guide us in. Once ready; the marshaller guided us in on the initial Tow In line and stopped us at the appropriate mark. The First Officer (F/O) ran the Tow In checklist and we shut down both engines and awaited the ground crew to contact us via the interphone. After a few minutes; he called and stated that they were ready to complete the Tow In. He called for brake release and according to the checklist script"; I responded and released the brakes to begin Tow In. Just as a note of reference; I've towed in the 777 several times at gate X and I'm very familiar with the process at this gate. With that said; as we began to pull forward; I noticed that the aircraft was closer to the second of two jetways (one to be attached to door 2L) than usual. It was not close enough to alarm me; or make mention to the tug driver; but it seemed closer than I've noticed before. As the driver made his very sharp turn towards the lead in line; the aircraft jerked and there was a loud accompanying "bang" from below. The aircraft initially came to a stop; but then began to slowly move backwards. The tug driver then "casually" called "set brakes"; as the aircraft was still moving backwards! Based on instinct and common sense; I did not touch the brakes initially. Those two things did not add up as to why he was asking for me to set brakes with aircraft movement. The F/O made a great comment and questioned whether there was a breakaway; so I quickly called the ground crew. He confirmed there was indeed a tow bar breakaway; so I gently came on the brakes to stop the aircraft movement. I'm not 100% sure; but I believe the F/O was also on the brakes as well which was good. As I surmised; the very sharp angle of his turn must have stressed out the tow bar and it gave way. Fortunately; there were mechanics downstairs that witnessed the entire event. The tug driver explained that the tow bar was broken and I confirmed the brakes were set. I also told him I wanted to talk to the mechanics before I released brakes; and only based on his request after a nose gear inspection. We also followed up with a call to maintenance who was surprisingly already in the loop. A mechanic soon called on the interphone and stated that he witnessed the entire event. I quote him ".. we're lucky no one was injured". He also seemed very agitated at the way the entire event unfolded. He and his crew began an inspection of the nose gear and asked me to cycle the nose gear through full range right and left. Fortunately; he found no damage and gave way to the ground crew once again. They brought another tow bar; connected; and we started the entire tow in process once again. This time successfully. The most disturbing parts of the entire event was not only the aircraft's proximity to the jetway; but the ground crew's lack of proper terminology and urgency during the tow bar breakaway. At no time did he use the term breakaway; and that cost a few seconds while we tried to figure out what was happening. The crew simply must use the term breakaway in order for us to grasp the actuality and severity of the situation - especially with us not being able to see what's taking place. A casual mention for us to "set brakes" during a breakaway simply will not do; and could lead to a more dangerous situation involving aircraft damage and/or injury. The ground crew's lack of urgency and not using the proper terminology was the greatest threat followed by the very large angle of the tow bar as he tried to make the turn. Obviously; I could not see what was taking place; but logic dictated there had to be a large angle on the tow bar for him to successfully make that turn without striking the jetway with the nose of the aircraft! Once he completed the tow in and I said "cleared to disconnect"; I asked for him to ask one of the Ramp leads or supervisors to come up to the flight deck to debrief. By then; there were a great deal of personnel at the nose of the aircraft onlooking and I assumed one had to be a lead or supervisor. Very; unfortunately; no one arrived to talk to me; but the mechanics did come up! They discussed the incident in detail from their perspective and we also briefed on an inbound and unrelated write up. I didn't ask or verify; but I only assumed the mechanics made a write up with all details involved in this incident."
Second reporter narrative
Before inbound I told my crew that I was new to towing in a flight. I was never trained to tow in a flight so I was uncomfortable to go through the whole tow-in process but because I was our dispatcher; I was told by one of my wing walkers who was dispatch qualified that he knew how to do a tow in gate so he proceeded to use the dispatch head set and told me to me bring in the plane with the push back tug. I asked him before I pushed which way I should faced the tug when connecting the tow bar. He told me to hook up the tug from the front facing the nose gear so that's what we did. After he brought the plane in; we proceeded to hook up the tow bar to the nose gear and then he gave me the 'brake set' hand signal and I gave him the 'break set' hand signal back. He then gave me the 'brakes release' hand signal and I gave him the 'brakes release' hand signal back. After brakes were released; he walked behind me to guide me on the line and I started reversing back towards the line. While reversing back to the line; I heard that the tow bar had snapped behind me and I immediately stopped on the scene. After stopping; my wing walker communicating with the pilot went to disconnect the tow bar. After he disconnected the tow bar; the plane rolled back and he immediately yelled out 'break away' to the pilot and the pilot was able to stop the plane. After that; Maintenance Control and the supervisors arrived on scene.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.