ERJ170 flight crew reported momentary uncommanded aircraft movement during pushback requiring the flight crew to apply the parking brake to regain control.
Synopsis
ERJ170 flight crew reported momentary uncommanded aircraft movement during pushback requiring the flight crew to apply the parking brake to regain control.
Narrative
After the aircraft was set up/checked and ready to go the Captain signaled to the ground crew to get on the headset after getting no response and got signaled back that they didn't have any. They asked to remove chocks and then signaled to release the parking break. We started rolling back and the captain and I both assumed we were getting pushed but we were just rolling back. The Marshaler gave some signal with his right hand that I and the captain did not recognize; looked like some kind of wave. I then expressed that it seemed like they were pushing us very quickly and then the captain pulled the parking break. He later explained that he saw another marshaler on the side with an X so that's why he did that. The plane jolted to a stop and they captain asked if the flight attendants were fine then made an announcement. Cause: Captain and I assumed normal pushback operations since we were not briefed by the ground crew of a no headset or power out operation. Suggestions: Captain and I should have followed company SOPs of always getting briefed if non normal operations and the ground crew should have also notified us of the situation as well.
Second reporter narrative
After all checks were accomplished and ready for pushback I tried to reach ground crew; there was no response.I had one person in front of aircraft with wands not illuminated although I could see he did have a pair in his hand. I made signals to be reached on headset; marshaler made a gesture of no headset and then proceeded with hand signals to remove chocks that I acknowledged for him to do. Next we signaled to release the parking brake assuming they were connected to the tug and I gave them hand signals to push back. We started to move away from the gate. I looked out the side window and saw the other marshaler with his illuminated wands in an X so I applied brakes without any deceleration of the aircraft. I then applied the parking brake to stop the movement of the aircraft.Cause: Lack of communication between flight crew and ground crew. No headset; only hand signals that in this case was in-sufficient. Ground crew did not do a face to face briefing prior to door closure that would have triggered a non normal push procedure. Suggestions: Briefing of the flight crew for a non normal procedure; including use of headset/handsignals. As an additional safety net; especially on a slanted ramp chocks should be installed behind the main wheels in cases where power out procedures are being accomplished from gate.In company pages in this case there should be a transparent caution notes regarding power out; caution do to a slanted ramp may cause aircraft to roll at brake release.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.