Air carrier flight crew reported during push-back having a miscommunication with the ground crew resulting in taking evasive action to stop the aircraft; the aircraft struck the tug damaging the aircraft.
Synopsis
Air carrier flight crew reported during push-back having a miscommunication with the ground crew resulting in taking evasive action to stop the aircraft; the aircraft struck the tug damaging the aircraft.
Narrative
During pushback I asked the tug driver if we were clear to start engine one which he responded clear to start one." After a successful start of engine number one; I asked if we could start engine two; which again; the tug driver cleared us to do so. A few moments later I heard the tug driver shout; "set brake; set brake; set brake!" and observed the guideman give the stop signal. I immediately reached to set the parking brake and at the same time felt the aircraft make contact with the tug. Prior to the tug driver shouting; "set brake;" I did not hear nor did I communicate to the driver that the brake was set. After setting the parking brake I asked the tug driver what had happened and he responded that he had told me to set the brake. I answered that I never heard him asking for the brake to be set and that I did not state "brake set." The only command I heard was the one mentioned above which was given too late to avoid aircraft contact with the tug. After learning what had happened we shut down both engines. I then contacted operations; dispatch and maintenance control to inform them of the situation. Ramp control was also made aware. I also communicated with the flight attendants and made the appropriate PA's to the passengers. It should be noted that during pushback I have no visual contact with the tug vehicle. It's also important to note that during the length of time that it took to disembark the passengers it was difficult to communicate with the ground crew. The ground crew had to make several headset changes to allow for proper communication. The decision was ultimately made to disembark the passengers via stairs and shuttle them to the terminal via bus.I am not aware of the exact cause of this incident but may have been a mechanical issue with the tug. Additionally; timely communication to set the parking brake could have prevented the aircraft from impacting the tug vehicle.It appeared to me that the headsets used by the ramp crew were intermittent. As mentioned in the description; after the aircraft made contact with the tug the ground crew had to swap headsets multiple times due to communication malfunctions. It is imperative to have high quality functional headsets throughout the pushback procedure."
Second reporter narrative
We began the push back with our tug driver. Our headsets were working fine and we were given no indication of any faults in our communication with ramp and we continued as normal. A slight Rain began during push when we were cleared by the ramper to Start # 1 engine. We started #1 engine. Then we received clearance from our ramper; now; to start #2. I commenced #2 start and after the 1-minute start was completed; I felt a movement of the tug. This coincided with what the rampers called the impact of the airplane into the tug; however it was not very distinguishable from a usual push operation. Maybe a second later; we heard the ramper saying; 'Set Brake!; repeated three times. Captain set parking brake and asked what had happened. *at no point prior to the impact did I or the CA hear the ramper say; "Set Brake'. And the CA did NOT acknowledge with "Brakes Set" at any point prior to impact.**It became apparent there were ramper headset issues since there were minutes (after collision and during management of all resources) where the flight deck could not hear the rampers and vice versa. The ramper headset was changed once or twice through the rest of the ordeal*We coordinated with dispatch; maintenance; operations; and ramp tower to advise them of our situation. For a long time; we awaited city approval to de-plane and a for bus to transport the passengers back to the concourse. Operations and maintenance decided we were unable to use air stairs on back doors because of height difference (this would've saved about another 30 minutes in planning on their part. 1 bus arrived at 98 min after #2 start and de-boarding began at 110min. Roughly XA:40 pm LocalI believe the leading cause was the ramper releasing the aircraft before the Captain acknowledged with "brakes set". Another cause MAY have been the faulty headset the ramper was using that inhibited our communication after-the-fact. A reemphasis on proper communication and phraseology for the rampers with the flight deck would have avoided the whole situation. A suggestion that could possibly have mitigated the issue is a properly-functioning headset for the ramper. As noted above; it did add to the confusion as we were assessing the situation and the rampers did need to switch headsets at least once through the ordeal."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.