B737-800 flight crew reported that after push back; they rolled forward a few feet after not setting the brakes properly and contacted the tow bar.
Synopsis
B737-800 flight crew reported that after push back; they rolled forward a few feet after not setting the brakes properly and contacted the tow bar.
Narrative
A reserve trip was assigned by Crew Scheduling: a 4-leg; maximum-duty day out of ZZZ with a XA:15 report time and a scheduled finish at XL:50. I had been experiencing delays throughout the day due to late inbound aircraft.The first portion consisted of a deadhead to ZZZ followed by operating the return flight; which was uneventful. My crew and I had a 2-hour sit prior to the next turn. During the break; I sat down for a late lunch before the turn to ZZZ1; scheduled to depart at XH:44 and return at XL:50.The inbound aircraft was late; causing us to block out behind schedul. Initial interphone contact with the pushback crew occurred around dusk; as the sun was setting rapidly. The tug driver's voice was low despite the volume being at maximum. I verified the hot-mic switch position to rule out an issue on my side. I normally conduct pushback communications via the cockpit speaker and handset; however; due to the poor audio quality; I placed my headset over my left ear in addition to using the speaker--a practice I never normally do. On initial call; First Officer calls for push clearance and we have about a 10 minute hold for congestion in alley. The push crew was very professional we exchanged standard pushback phraseology; we finally obtained pushback clearance; and began moving to the ramp-assigned spot. During the push; we were cleared to start both engines and did so. Upon reaching the stop point; ambient light was lost; it was now fully dark in the flight deck. I commented to the First Officer; It got dark quick."The tug driver requested that I set the parking brake. I performed what I believed was the normal parking-brake-set procedure; then advised him; "Brakes set" along with standard disconnect phraseology (which I have done over 1000 times being in the Captain seat for over 5 years). As the ramp crew began the disconnect sequence; I reached to quickly adjust the cockpit lighting for night operations. Normally; on a typical night pushback; the dome lights are on max brightness; so the ramp team can maintain visual contact with me during the push process.At that moment; the tug driver transmitted; "Confirm brakes are set." I immediately applied full toe-brake pressure with both feet and set the parking brake handle--everything happened very quickly. The ramp crew then advised that the aircraft had rolled forward approximately 2 feet; resulting in tow-bar damage.It was very dark outside ; and neither I nor the First Officer perceived any aircraft movement.We confirmed no injuries occurred. Both engines were shut down; Maintenance was coordinated for an aircraft inspection prior to further movement; and ramp arranged a different tug to return us to the original gate XX.Cause: Double and triple check the brake handle is engaged before communicating to push crew."
Second reporter narrative
On push back; we received clearance from ground crew to start engines. The Captain directed me to start engine number 2 then 1. As engine 1 was starting; I heard the Captain say parking brake set; clear to disconnect." The engine had stabilized; I set the engine bleeds. With us being stopped on the ramp; I realized based off the current time that there should be a new ATIS. I sent off for a new ATIS via ACARS. At that time I felt the tow bar get disconnected; then a violent vibration. I looked up and saw the push back tug shaking violently and much closer than normal. I initially thought the tug hit the aircraft. The ground crew said the aircraft rolled forward; over the tow bar. I looked down and saw the red parking brake light; then I looked at the hydraulic panel on the overhead. Everything was normal; hydraulic lights out. I checked the hydraulic system page and saw normal pressures. The ground crew advised that we needed to call Maintenance. I called Maintenance. They advised that they would send somebody and to put it in the log book. Maintenance did an inspection; and determined we needed to go back to the gate for more inspections. Upon being towed to the gate a ramp manager stated that they reviewed the incident and aircraft did roll forward onto the tow bar approximately 3 to 4 feet. It is possible that when the Captain went to set the brake; it didn't fully set. It is also possible during the aircraft rolling over the tow bar; the Captain reset the brake before I looked down at the brake light.Cause: Failure of proper pilot monitoring to insure the captain properly set the parking brake due to task saturation."
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.