B737 flight crew reported the electronic and equipment doors were not closed to maintenance. Maintenance failed to close one door and MEL the other resulted in pressurization failure and overweight landing at departure airport.
Synopsis
B737 flight crew reported the electronic and equipment doors were not closed to maintenance. Maintenance failed to close one door and MEL the other resulted in pressurization failure and overweight landing at departure airport.
Narrative
During the walk around I noticed the E & E doors were opened since we were the first flight of the day to ZZZZ. I assumed the proper personnel would come and close the doors prior to push. When we went to push we saw the EQUIP light was still on indicating the doors were still open. We called maintenance to come and secure the doors; when he arrived he closed the forward E & E door multiple times and the light remained illuminated. He determined it must be the sensor and decided we would defer the sensor. We reconnected the jet bridge and maintenance came on board and deferred the sensor. We followed the new MEL which instructed us to have ground personnel verify the doors are closed and locked. We pushed back and on takeoff could immediately feel the airplane was not properly pressurizing and confirmed on the overhead panel that the cabin pressure was climbing with our altitude. We leveled off at 5;000 [ft.] and told ATC we would likely be returning to ZZZ and would like vectors to give ourselves time to prepare. I was flying and the Captain gave me the radios and started working on checklists and coordinating with Dispatch. Together we decided an overweight landing was the best course of action. The Captain ran the non-routine landing considerations checklist and we received vectors back to Runway XX in ZZZ. We landed with a very low rate of decent in ZZZ at 156;700 lbs without incident. Upon arriving to the new gate maintenance was waiting for us. They noticed the aft E & E door was still open. When we called maintenance earlier they must have only looked at the more obvious forward door and neglected to check the aft door. This was also missed when we asked to confirm all doors were closed per the MEL. We received a new aircraft assignment and after receiving bags and fuel we made our way to ZZZZ.Cause - The doors must have been left open by maintenance or whoever conducted the security check that morning. We called maintenance to close the doors and they should have checked both doors since they are connected to the same switch.Suggestions - Multiple doors can utilize the same MEL; the E & E doors should have their own MEL that has more emphasis on both doors. We had no way of knowing the maintenance technician didn't check both doors. Prior to MELing there should have been a troubleshooting checklist to follow that emphasized both doors because the technician was eager to MEL the sensor when it was a simple fix.
Second reporter narrative
Several access doors were open during pre-flight. Prior to push back I alerted the push crew the EQUIP light on the overhead panel was still illuminated. The push crew stated the forward E&E door was not closed. Maintenance was asked to come out and secure the open door. The door was properly secured; but the EQUIP light remained illuminated. Maintenance decided the issue could be addressed using MELXX-XX. The aircraft logbook was properly signed off and the flight continued. Aircraft failed to pressurize properly after takeoff. Returned to ZZZ and executed an overweight landing after conferring with Dispatch. Subsequent landing was exceptionally smooth. Normal braking was used resulting in a nominal landing distance followed by an uneventful taxi back to the gate. Once back at the gate it was discovered the main E&E door; located aft of the nose landing gear; was open.Cause - Access doors being improperly left open. Maintenance personnel failed to ensure all doors were closed after be alerted to the flight deck EQUIP light.Suggestions - Ground and maintenance personnel need to visually and physically verify all access doors and panels are properly secured.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.