Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 136; Flight Crew Total 2245; Flight Crew Type 2245
Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control
Flight Crew Regained Aircraft Control; Flight Crew Took Evasive Action
Human Factors
Pushing back from [gate] in ZZZ. We were anticipating a taxi to Runway XXL and the FMGC was set up to reflect that. Called for pushback clearance was told to push tail south to the grass and expect Runway XY for departure. Being a ZZZ1 based crew these instructions were a little foreign to us; but were relayed to the ground crew and pushback began. Communication with our ground personnel was a little strained as the tug drive had a little bit of an accent and was hard to make out. The instructions to expect Runway XY required us to revise our pre-departure plan to now include the starting of the second motor due to the short taxi. During the pushback; I was heads down resetting the box and loading the data for our new runway of departure. I was listening in on intercom but wasn't giving it my fully attention; as I was starting the engines. The pushback was complete right around the same time as I verified the need to start the second motor with the Captain. I do not recall ever hearing 'pushback complete; set brake' from the ground crew; but it may have been stated as all other procedure from there seemed to occur normally. The tug driver disconnected and ground personnel released us.The Captain was heads down verifying our new speeds and departure procedure in the FMGC as I finished my after start flow and shutdown the APU. It was about this time that we both looked up as the aircraft was slowly rolling forward and gaining a little speed. The Captain and I both got on the brakes and brought the aircraft to a stop a little abruptly; but not violently. We estimate that we probably rolled about 10-20 ft. forward unaware. We did not come into contact with anything and after verifying that the flight attendants we all ok from our sudden stop; we continued on our way.
A320 Captain reported non-standard communication with ground crew during pushback caused the aircraft to roll forward after being disconnected.