B737-400
Flight Crew Air Transport Pilot (ATP)
Distraction; Situational Awareness; Training / Qualification
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance
Flight Crew Returned To Departure Airport; General Maintenance Action
Human Factors; Procedure
After the external pre-flight by the First Officer; I noticed the EQUIP door light was illuminated. We called Maintenance and a Mechanic came out and inspected the equip door and assured us that it was closed securely; and they would MEL the EQUIP light. The discrepancy was entered into the logbook and the MEL was applied. The Mechanic showed us the MEL and mentioned that we would need to visually inspect it in our next destination; and that he had checked it. Push-back and taxi was normal. On takeoff roll approximately 120 KTS there was a lot of air noise; and after takeoff the aircraft did not pressurize. We requested a straight out and told Departure Control we would return. I transferred aircraft control to the First Officer. I ran the overweight landing checklists and returned to the departure airport. We decided to land overweight because of the extreme noise. It was very difficult to communicate with each other and ATC. The landing was only 1;600 LBS overweight and touchdown was less that 200 FPM. The First Officer inspected the nose area and the equip door in front of the nose gear was open. He closed the door and the light extinguished. The communication was difficult because of the noise. The First Officer's experience level and pilot handling are outstanding. I can't believe that the First Officer would miss an open door on the pre-flight; the Mechanic could miss it when he came out to check equip doors; and the push-back crew would miss it.
A B737 EQUIP door light was on during preflight so a Mechanic deferred the light. After takeoff the aircraft would not pressurize and the noise level was so high the crew returned to land overweight where the door was found open.