Air carrier flight crew reported miscommunication with the ground crew resulted in an uncommanded aircraft movement and loss of aircraft control.
Synopsis
Air carrier flight crew reported miscommunication with the ground crew resulted in an uncommanded aircraft movement and loss of aircraft control.
Narrative
Awaiting pushback in DCA; our ramp crew met us from the adjacent gate and plugged into the airplane so we could communicate via headsets. After being given the safety briefing; the ramp crew member told me he was ready to capture the airplane. I asked if he was ready for the parking break release to which he replied 'yes'. I released the parking brake and the aircraft slowly rolled back about 6 inches. Right when I realized the aircraft was rolling back; the ramp crew member told me to set the brake because he didn't have the airplane. I slowly set the parking brake and the airplane came to a stop. There were no injuries and there was no imminent threat to the aircraft. The ramp crew reconnected to the airplane; and we pushed back as normal and the rest of the flight was routine.Cause: This event was caused by poor communication between the ramp and the flight deck. After being told I was cleared to release the parking brake I trusted that the ramp crew had control of the airplane when they did not. Suggestions: In the future I would take extra precautions to triple check and ensure that all parties are ready for the parking brake to be released especially after the ramp crew had rushed over from another gate. Additionally; ramp crews should be fully briefed on company SOPs for capturing an aircraft and proper communication on what being ready for the parking brake release means.
Second reporter narrative
Waiting to push in DCA. Our ramp crew was sharing the tug from the next gate over. They came over once they finished pushing the other aircraft and plugged into the aircraft. Safety briefing was made and then the ramp crew told us they were ready to capture the airplane. The Captain asked 'Are you ready for the parking brake release?'. The ramp crew replied 'Yes.' The captain then release the parking brake and we noticed that the aircraft began to slowly roll back. As we both realized this the ramp crew told us to set the brakes due to him not being able to capture the aircraft. The Captain set the parking brake slowly and stopped the aircraft. The supervisor came over to take over the capture and pushback of the aircraft. Pushback proceeded as normal and flight was normal.Cause: Lack of clear communication from ramp to flight deck.Suggestions: Proper phraseology from ramp crew. Ensure ramp is ready for capture and push. Less pressure on ramp crews sharing tugs to rush a push. Operations need to be better aware of company SOPs and communication.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.