Narrative:

We were operating a flight delayed approximately 3 1/2 hrs. We showed up to the aircraft and everything was normal. We ran all of the appropriate checklists and everything was sop. We called center on the ground and got our IFR clearance with a hold for release time as the tower was closed. Agent asked if it was ok to close and we said yes. I established communication with ground crew and they requested permission for pushback. We ran the 'before push' checklist and I called them back and reported 'brakes released; cleared to push'. During pushback ground crew called and said 'cleared to start both engines'. I acknowledged the ground crew and asked the first officer (first officer) to start both engines. While this was happening we heard a flight on the radio inbound and I was thinking about how this was going to work out as they were doing a straight in approach and we were going to taxi to depart the opposite runway. All of this time I had my eyes out of the cockpit and was monitoring the pushback and watching the ground crew. Next I heard the ground crew state 'set brakes'. I reached down and set the parking brake and thought I saw the red parking brake light illuminate. I stated 'brakes set' while keeping my eyes on the ground crew. Next thing I knew was I was feeling a weird vibration under the aircraft and I was looking outside trying to figure out what was going on and if the ground crew was having trouble disconnecting the tow bar. Then the first officer stated 'the parking brakes not set'. I then immediately reached down and reset the parking brake. During this time we had no communication from the ground crew that the aircraft was moving or that there was anything wrong. I called the ground crew and asked what was going on and they said the parking brake wasn't set. I said we realized that and reset it. We had maintenance come out and do a quick inspection and they said they wanted us to taxi to the gate so they could do a more thorough inspection. Before I moved the aircraft I called the lead flight attendant and told them what had happened and that we would be returning to the gate and then I made a PA to the passengers explaining to them we would be returning to the gate. We went through an after landing flow and when the ground crew was back at the gate we taxied the aircraft back to the gate. After returning to the gate we did the parking checklist and once I was satisfied everything was under control I called the [duty manager] and informed him of who I was and what had just happened. We were getting no information from the local station so I exited the aircraft to go talk to maintenance and visually check for myself what had happened. That is when maintenance told me they were cancelling the flight as a more in depth inspection of the nose gear would be required. I returned to the cockpit and told the crew what was going to happen. The station deplaned the passengers and we as a crew remained on the aircraft trying to communicate with scheduling and see what their plan was. After a while we accomplished the termination check list and deplaned the aircraft. The first officer and I remained at the airport until all of the passengers had left in taxis for hotels and we knew the flight attendants had rooms and I knew what was going on with their schedule. Both the flight attendants and the cockpit crew left the airport at the same time. I have always thought I was very vigilant of the parking brake. I even state to my first officer's when I set the parking brake during lengthy taxis. All SOP's and checklists were followed and adhered to. In retrospect I know I will be much more vigilant of verifying that the parking brake is actually set when I call 'parking brake set'. The only thing I can think that happened is that I had a false set of the brake or somehow I may have kicked the brakes off without realizing it. I think a good procedure to implement in the future would be for the first officer's to visualize and verbalize on the push back that the parking brake is indeed set with a positive indication. Another good procedure I feel should be implemented is that when the ground crew sees or feels anything out of the ordinary when they are in headset communication with the flight crew is that they should verbalize that concern immediately and request 'brakes set'. During this whole incident we had no communication with the headset operator that anything was wrong until I called down to check what was going on after I reset the brake. Again; we had no call that anything was out of the ordinary as I had no sense of aircraft movement. I just heard strange noises and thought they were having difficulty disconnecting the tow bar.

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Original NASA ASRS Text

Title: B737 flight crew reported setting the parking brake after pushback then starting engines. At some point it becomes apparent that the brake is not set and the nose gear makes contact with the tow bar as the aircraft moved forward unnoticed by the crew. Maintenance determines that an inspection is necessary and the flight is canceled.

Narrative: We were operating a flight delayed approximately 3 1/2 hrs. We showed up to the aircraft and everything was normal. We ran all of the appropriate checklists and everything was sop. We called center on the ground and got our IFR clearance with a hold for release time as the tower was closed. Agent asked if it was ok to close and we said yes. I established communication with ground crew and they requested permission for pushback. We ran the 'before push' checklist and I called them back and reported 'brakes released; cleared to push'. During pushback ground crew called and said 'cleared to start both engines'. I acknowledged the ground crew and asked the First Officer (FO) to start both engines. While this was happening we heard a flight on the radio inbound and I was thinking about how this was going to work out as they were doing a straight in approach and we were going to taxi to depart the opposite runway. All of this time I had my eyes out of the cockpit and was monitoring the pushback and watching the ground crew. Next I heard the ground crew state 'set brakes'. I reached down and set the parking brake and thought I saw the red parking brake light illuminate. I stated 'brakes set' while keeping my eyes on the ground crew. Next thing I knew was I was feeling a weird vibration under the aircraft and I was looking outside trying to figure out what was going on and if the ground crew was having trouble disconnecting the tow bar. Then the FO stated 'the parking brakes not set'. I then immediately reached down and reset the parking brake. During this time we had NO communication from the ground crew that the aircraft was moving or that there was anything wrong. I called the ground crew and asked what was going on and they said the parking brake wasn't set. I said we realized that and reset it. We had maintenance come out and do a quick inspection and they said they wanted us to taxi to the gate so they could do a more thorough inspection. Before I moved the aircraft I called the lead Flight Attendant and told them what had happened and that we would be returning to the gate and then I made a PA to the passengers explaining to them we would be returning to the gate. We went through an after landing flow and when the ground crew was back at the gate we taxied the aircraft back to the gate. After returning to the gate we did the parking checklist and once I was satisfied everything was under control I called the [Duty Manager] and informed him of who I was and what had just happened. We were getting no information from the local station so I exited the aircraft to go talk to maintenance and visually check for myself what had happened. That is when maintenance told me they were cancelling the flight as a more in depth inspection of the nose gear would be required. I returned to the cockpit and told the crew what was going to happen. The station deplaned the passengers and we as a crew remained on the aircraft trying to communicate with scheduling and see what their plan was. After a while we accomplished the termination check list and deplaned the aircraft. The First Officer and I remained at the airport until all of the passengers had left in taxis for hotels and we knew the flight attendants had rooms and I knew what was going on with their schedule. Both the flight attendants and the cockpit crew left the airport at the same time. I have always thought I was very vigilant of the parking brake. I even state to my First Officer's when I set the parking brake during lengthy taxis. All SOP's and checklists were followed and adhered to. In retrospect I know I will be much more vigilant of verifying that the parking brake is actually set when I call 'parking brake set'. The only thing I can think that happened is that I had a false set of the brake or somehow I may have kicked the brakes off without realizing it. I think a good procedure to implement in the future would be for the First Officer's to visualize and verbalize on the push back that the parking brake is indeed set with a positive indication. Another good procedure I feel should be implemented is that when the ground crew sees or feels anything out of the ordinary when they are in headset communication with the flight crew is that they should verbalize that concern immediately and request 'brakes set'. During this whole incident we had NO communication with the headset operator that anything was wrong until I called down to check what was going on after I reset the brake. Again; we had NO call that anything was out of the ordinary as I had no sense of aircraft movement. I just heard strange noises and thought they were having difficulty disconnecting the tow bar.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.