2024-04 · NASA ASRS report 2105992
EMB 170/175 flight crew reported the aircraft became disconnected from tow bar during pushback resulting in the aircraft rolling uncommanded. Captain set parking brake to stop aircraft.
During push back the aircraft became disconnected from tow bar. Ramp asked me to set brakes. There was confusion because I did not know we were disconnected and I knew we were in motion. I finally realized we were rolling towards the tow vehicle and the tow vehicle was not moving so I set the emergency brake. Ramp told me the pin was not installed in the tow bar keeping us secured. They reported the tow bar did not contact the aircraft in any way and there was not damage. I did not write up the aircraft becoming disconnected from the tow bar before departing the station. It was very dark VMC. I did not hear if the tug driver told me we were disconnected; all I heard was to set the brake. Ramp interphone was a little hard to hear. It was my belief at the time as long as the shear pin did not break or the aircraft did not come into contact with anything a write up/inspection was not required.The tow bar becoming disconnected was not avoidable by the crew. In the future I know if the aircraft unintentionally becomes disconnected I will make a write up.
Upon pushback in ZZZ; the tow bar came apart (one end remained connected to the aircraft; and the other end was still connected to the tug. It separated in the middle). We were not aware of it at the time. It was too dark outside to have any visual reference to anything stationary outside. I was heads down starting engine #1 and fixated on the EICAS display during engine start. The ground personnel said to 'set brakes' over the ramp intercom channel. We could tell that we were still moving (although we weren't sure of the direction); so the Captain (CA) hesitated to set the parking brake. When he was able to see that we were rolling toward the tug; he set the parking brake and the aircraft came to an abrupt stop. When the CA asked the ground personnel if the shear pin had broken; they responded that it had not; and that the bar had just separated in the middle because someone forgot to put the pin in. We discussed whether it required a maintenance write up; and we were both under the impression that if the pin did not break - it did not. We finished the remaining checklists; and departed uneventfully. When we were deplaning in ZZZ1; the FWD Flight Attendant (FA) notified us that she had hurt her shoulder in the abrupt stop and needed medical attention (she had not notified me of this when she answered the PA during the 'Before Takeoff' checklist on departure. Cause: Tow bar separation. Faulty equipment use. Unclear communication from ground personnel. Poor lighting. Delayed communication from FA that she had experienced an injury. Suggestions: Ground equipment should undergo some kind of multi step verification that it is safe to use (especially when used to move aircraft with people on board). Better lighting on the ramp at ZZZ (at least enough to see motion relative to stationary objects from the flight deck). More concise communication from the ground crew about the nature of what was happening would have allowed the CA to slowly apply the aircraft's brakes rather than simply pulling the parking brake. Better communication between flight deck and cabin when there is some kind of aircraft motion that is out of the ordinary. Had we been more familiar with the SOP's regarding 'ANY' separation of the tow bar; we would have called for a maintenance inspection and that likely would've given us time to discover that the FA was hurt.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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