EMB-175 flight crew reported the aircraft rolled uncommanded during pushback. Captain applied brakes to stop.
Synopsis
EMB-175 flight crew reported the aircraft rolled uncommanded during pushback. Captain applied brakes to stop.
Narrative
During pushback from gate XX; we have just received clearance to push. At this time the ground crew has not contacted us over the headset; even though they were present and appeared ready for push. After two attempts the captain reverted to hand signals. I saw the captain use the hand signal signifying parking brake release; and after apparent reciprocation; released the parking brake. However we noticed we started to roll a little; and promptly reengaged the parking brake. After the event the ground crew eventually established headset contact; and we successfully pushed without any safety; or operational hazard.Cause: Miscommunication with hand signals with ramp crew.Suggestions: When ramp crew established radio contact; the crew stated they did the hand signals for chalk removal; however the captain very clearly gave the signal for parking brake release. The ground crew when seeing that should have reconfirmed with the appropriate hand signals; or established headset contact earlier.
Second reporter narrative
After inputting our closeout data and running the before start checklist; we were preparing for pushback. We were unable to communicate with the rampers and eventually got their attention with the ramp horn. One of the rampers got onto the ground support equipment and put the headset on but did not communicate with us. He got off the equipment walked to my side of the aircraft and gave me the chocks pulled" and "brake release signals". I signaled back and released the brake. We looked down to switch over to comm 1 for clearance. When I looked up I noticed the aircraft slowly moving backwards. At first I thought they were pushing us without clearance so I turned on the AC pumps to apply smooth brake pressure. We then realized the aircraft was rolling backwards because they hadn't connected it to the tug. We set the parking brake again once we came to a stop. I don't think we rolled more than a couple feet. The ramper then got back on the tug and was able to establish communication with us through the headset. I clarified what happened and he said he was just wanting the chocks pulled. They connected the tug and told us they were ready to push out. I confirmed all secure below; fod walk complete; and steering was disconnected; but the ground crew were not using standard phraseology. Once cleared to push we completed the pushback without further incident. I let expectation bias take over and incorrectly assumed that the headset had failed. I saw that we had enough rampers to do a no communication pushback which led me to believe the ground crew was ready for the pushback. With the lack of standard phraseology once we were able to communicate I am guessing the ramp crew was just attempting to get an on time departure with the brake release.In the future I will make a better effort to verify all equipment is working prior to a push back. I will also make sure in the event of a no headset push back that I will keep my head up and outside to make sure there is no unintended aircraft movement."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.