Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Situational Awareness; Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Flight Crew Took Evasive Action
Human Factors
We were at Gate X. When we called for push; ramp cleared us to push tail south and to leave enough room for Aircraft Y to push as well. As we were completing our push ; ramp called us to keep pushing to keep a bit more room for Aircraft Y to push. I communicated this to the ground crew and we kept pushing. Ground crew then told us to set brakes and I said ' Standby; let me ask ramp if this was deep enough' Ground crew said 'Can't go any further as Gate Y is also pushing'.At this moment; I felt that the ground crew was disconnecting and I jumped on the brakes just as we started moving. The ground crew said 'we are disconnected'. They showed me the pin and walked off. I set the parking brake and waved them off. I was aware of the uncommanded aircraft movement bulletin and had this on my mind. We did have a few interruptions during this push which may have been different for the ground crew. Maybe we could remind the ground crew to wait for the Captains 'cleared to disconnect' message. Strict adherence to standard phraseology and awareness will be the key to avoiding these situations. Another suggestion here would be to have ramp give specific push back instructions eg 'Push tail South; release abeam Gate'. This would have cleared any doubt and would have reduced our flight deck to ground comms and we could have reverted to more standard and 'normal' sequence of events.
While at the gate I called for pushback. The instructions were to push back far enough to leave room for an adjacent jet to push back. The captain called for push and we were pushed back. The ground crew stopped us; and ramp asked us to go further back so we relayed to the ground crew. The second time we stopped the Captain asked me to call ramp to see if that was enough room for the other aircraft. While I was making the call; the ground crew disconnected and the Captain had to quickly get on the brakes. Post radio call the Captain informed me that he had not requested the disconnect. [Cause was] Expectations bias and complacency [Suggest] Adherence to standard comms.
Airline flight crew reported the pushback ground crew disconnected the tow bar without informing the Captain to set brakes.