EMB-170 flight crew reported during pushback they started one engine which caused the aircraft to roll forward due to the ground crew having disconnected the tug without notifying the flight crew.
Synopsis
EMB-170 flight crew reported during pushback they started one engine which caused the aircraft to roll forward due to the ground crew having disconnected the tug without notifying the flight crew.
Narrative
During pushback from the gate; ramp personnel were required to stop the push of the aircraft from the gate half way through the push because the tug was experiencing mechanical problems. The aircraft was dropped with coordination of Ground Control with plenty of space to begin a safe taxi. Ramp personnel were told they had permission to drop the aircraft and they began to make their preparations to drop. Ramp gave the flight crew permission to start Engine 1. Shortly after ramp began to seemingly remove the tug from the aircraft; the aircraft began to move forward. It appeared the tug was still attached and moving the aircraft into a more appropriate alignment next to Taxiway X. The flight crew had no communication with the tug and was hesitant to hit the brakes on the concern the tug was attached and damage the aircraft or other equipment. It was not until the centerline wing walker; currently stationed in front of the flight deck in view of the crew holding his wands in an 'X' to indicate to the flight crew to hold; began to make several and continuous steps backward; did the crew realize something was wrong. At this moment the Captain saw the tug and tow bar drive off and back to the gates. The tug never gave any word to the flight crew that the push was complete and to set brakes. Because the brakes were never set; the aircraft began to move forward after the tug and tow were removed and the thrust of a now idle engine was enough to create forward motion toward the retreating tug and crew. The Captain immediately stopped the aircraft and set the parking brake. The crew received the official wave off and began with the after start checklist and continued the flight. I recommend crews be assertive and ask if they can set the parking brake if the tug does not tell them. ZZZ ramp personnel receive immediate training to communicate with the crew to set brakes after the push is complete.
Second reporter narrative
Pushback from the gate was coordinated with the ground crew. The ground crew requested to stop halfway through the push due to tug complications. Engine 1 was started with positive communication with the tug driver. There was no communication instructing the parking brake to be set or to disconnect. The aircraft started moving forward; which I thought was the tug pulling us forward. However; the wingwalker holding the orange wand 'X' was taking steps backwards. I realized that we were not connected to the tug when it pulled out to the left from under the airplane and we were still moving forward. I braked and in total we moved about 15 ft. The tug drove back towards the gate and the ramp agent with the X gave a wave off.In summary; the ground crew disconnected without any communication or confirmation of the brake being set and pulled out towards the running engine as we started to roll forward. Brakes were set; and no further incident. Communication from the ground crew to set the brake and that they were planning to disconnect.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.