2024-04 · NASA ASRS report 2107787
Air carrier flight crew reported the aircraft rolled forward uncommanded during pushback procedure. The Captain turned on the hydraulic pumps and the aircraft came to a stop.
We were a crew of four and had completed all preflight duties when a mechanic came up to ask us to start the APU so he could remove ground power. We started the APU but before we could switch power the other mechanic pulled the ground power and the aircraft went dark except for the battery items. We again completed preflight duties and navigation checks to make sure the aircraft was set up correctly. Just before departure time we completed the load complete electronic verifications. The FO2 left the flight deck to close the L1 door and walk the deck. The FO called Ramp Control and stated load complete. Ramp said the tug was behind us and would be there shortly and to call him back when ready for pushback. The mechanic then connected to the intercom and stated the tug would be there shortly. Since it was now departure time; I said lights out; brakes set clear to remove chocks and stairs. Confirm gear pins and pitot covers are removed and clear to pressurize hydraulics. The mechanic replied; gear pins and pitot covers removed. After a short pause he said he was disconnecting from the aircraft and would be back in a couple of minutes. We briefly discussed not doing the before start checklist since he had not said removing chocks and stairs or cleared to pressurize. Our mental model was that he was probably hooking up the tug or maybe the steering bypass pin but I could not inquire since he had disconnected. Approximately one to two minutes later I felt aircraft movement and looked out the left window to see we were moving forward and seemingly picking up speed as if the tug was pulling us. I was completely startled but realized after a moment that we should not be moving. My right hand went instinctively to the parking brake handle and it was set; I then pushed the toe bakes to the floor with no effect and realized we had no brake pressure and reached up and pressurized the number 4 hydraulic demand pump. The aircraft stopped. During these few seconds both FOs on the flight deck were calling for brakes and the mechanic had reconnected and called out brakes over the intercom. I immediately said brakes set to the mechanic and then asked was anyone injured. He replied we are all good. I then asked if the aircraft hit anything and he again replied we were all good and no damage was done. From the flight deck it appeared the nose of the aircraft was over the blast fence. The mechanic then coordinated another tug to pull us back away from the fence. During this time; I received a call from Operations asking how we were doing and I quickly relayed that we had rolled forward but had stopped the aircraft and no injuries were reported and the aircraft had not been damaged. During pull back from the fence area the ACARS registered an out time. The mechanics did a thorough inspection to the front of the aircraft and found no damage. They brought back the stairs and the mechanic came up and signed off the entry in the logbook with a new logbook page and a fresh Airworthiness Release and signature. We then closed the door and called ramp for pushback and engine start which were normal and we departed without further issue.Preventative measures would include standard phraseology when responding to my initial communication. I do not know if the mechanic was distracted by something but he didn't respond by saying removing chocks and stairs and cleared to pressurize hydraulics or he could have said standby. Also; I am unclear as to why he would disconnect from the intercom at that particular moment.
Communication was confirmed with the ground engineer as we prepared to commence pushback from Spot XX at Ramp X in ZZZ.Whilst verifying the removal of stairs and chocks; the Ground Engineer confirmed the stairs were removed but did not confirm the removal of the chocks from the aircraft or the connection of the pushback tug.Upon confirming the removal of pitot covers and gear pins and ensuring clearance to pressurize hydraulics; the Ground Engineer responded; gear pins and pitot covers removed. I'm going to disconnect for a minute and get back to you; and abruptly disconnected his headset with an audible click; cutting off communication with the flight deck.As we waited for the ground engineer to re-establish communication; the aircraft began to move forward slowly and then accelerated. The Captain attempted to apply the brakes and set the park brake handle; but without the hydraulic panel set for pushback; there was no brake pressure to stop the movement.At this critical moment; the Ground Engineer re-established communication and urgently transmitted; brakes; brakes.The Captain promptly adjusted the hydraulic panel; switching the #4 and #1 hydraulic demand pumps to aux (Auxiliary) and the remaining pumps to auto; which allowed the aircraft to slow down and eventually come to a stop.After confirming with the Ground Engineer; we were informed that no personnel were harmed; and there was no damage to the aircraft or nearby ground equipment.This incident highlights the importance of using standardized phraseology and thorough verification. Additionally; the Ground Engineer expressed concerns about ramp personnel removing chocks without proper communications between them (ramp personnel and Maintenance); emphasizing the need for strict adherence to safety protocols.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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