EMB-170 flight crew reported loss of aircraft control during pushback procedure.
Synopsis
EMB-170 flight crew reported loss of aircraft control during pushback procedure.
Narrative
The airplane began to roll/move under its own power (engine 1 start completed already) when the tug disconnected from the airplane. The last communication heard from the ramp to the flight crew was the clearance to start engine 1. The Captain was concerned the ramp crew was disconnecting from the airplane during the last movement felt during the pushback. Initially; I thought the nose was being moved slightly more north and the pushback was still ongoing; as there was no communication heard that the pushback was complete; or instructions to set the parking brake. In the following several seconds; the airplane began to move east on the alley; towards the ground crew; the Captain inquired several times and attempted to get communication from the ramp to confirm to set the parking brake; while sounding the horn several times; and making hand signals for parking brake set. I cannot remember if I flashed the taxi nose light or not. I just remember doing simultaneous communication efforts as things were escalating fast. There was no verbal or visual acknowledgement from the ramp crew. There appeared to be eye contact from the ramp crew along with the 'X' with wands. The only other visual indicator was one of the agents placing his hand on his chest; seemingly concerned over the event. The Captain promptly applied firm pressure to the brake pedals; following by emergency brake application. The ground crew proceeded to give a salute to the flight crew and left the area. The Captain then called the cabin to ensure there were no injuries and confirmed nothing abnormal in the cabin. The Captain then called operations to ask the ramp crew to confirm there was no injuries or damage and the operations personnel said the ramp crew acknowledged our message but only said 'ok.' Cause: Lack of positive communication between ramp crew and flight crew that pushback was complete; parking brake was to be set; parking brake was actually set at the appropriate time; and that the ramp crew was cleared to disconnect the inter phone. Suggestions: Tug driver being the one connected to headset with flight crew. Every second during pushback communication is critical and I believe this is an increased risk if this Ramp crew member cannot directly communicate with the pilots; especially when disconnecting from the airplane. At this stage in the pushback; there is not line of sight between them and the flight crew for hand signals. I do not know in this incident if the tug driver was connected or not. The agent (presumably the crew chief) making the X with the wands appeared to be wearing a X headset; though it was during nighttime conditions.
Second reporter narrative
Flight crew made positive contact with pushback tug prior to pushback. During pushback; crew was notified that they were cleared to start #1. Following engine start on pushback; ground crew disconnected interphone and tug without notification to flight crew. Airplane began a slow roll forward under idle thrust when tug was disconnected. CA attempted to signal rampers with horn and nosewheel light; however no further communication was ever received from rampers. CA applied toe brakes to stop aircraft from rolling and damaging equipment and personnel. CA called the cabin crew to verify no one was injured; then contacted ops to report incident; and verify no damage to ground equipment and aircraft. Cause: Flight deck had not given any instruction that the ground crew was cleared to disconnect interphone; and gave no notification that the parking brake was set. No communication was received from ground crew prior to them disconnecting interphone; nor that tug was releasing the aircraft. Airplane began rolling after engine 1 was started. Suggestions: CA must be able to notify ground when parking brake is set and when they can disconnect interphone. Without knowledge that the tug was to be disconnected; flight crew has no way to know if aircraft is being pulled forward by tug; or if aircraft is moving under its own power.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.