EMB ERJ 170/175 ER/LR
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Troubleshooting; Time Pressure; Communication Breakdown; Workload
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown
Flight Crew Overcame Equipment Problem
Aircraft; Human Factors; Procedure
We had to reopen the Main Cabin Door and the jetbridge had to be pulled back to the plane due to a change in the release requiring more fuel. I'm unsure as to how the door was missed; as I thought we had pushed on it and checked it the second time we locked it and the flight attendant even said she gave it a pull after we locked it. However; on takeoff I heard a loud bang coming from behind me and I stayed focused on my takeoff. I'm not certain at what time the captain reclosed the door; but in cruise he did mention that he had to unlock the lock in order to re latch it and lock it. My memory serves that the door was locked when we did the checklist.We had flap gap seals damaged on the aircraft on initial walk around. Maintenance came out and was irritated at the captain for writing it up. I offered a printed flap aerodynamic seal inspection task given to me from previous A&P's to help him find a quick solution as that is what previous mechanics have used for write ups for the same seals . (I typically run into these particular seals being damaged at least once per trip). He got angry at me and told me its not my place to offer help. After putting an CDL on the plane that required a lower altitude on the release due to a performance hit he sent a message saying we were released at Time. We didn't actually receive the release until around Time. The mechanic had either forgotten or based on his demeanor intentionally delayed the flight to get under our skin. After being released; we did the before start checklist again and caught that the fuel needed to be added due to the new release. We waited again for fuel and a gate agent to come. Ultimately we were delayed about 51 minutes which likely played a role.My personal adjustment to this is to make sure I push on the door every time I read the below the line before start checklist as I believe the lights on the door lock corresponded to it being locked.
First Officer reported cockpit door came open on takeoff and was closed and resecured by The Captain.