B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Workload; Communication Breakdown; Time Pressure; Confusion
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport; Flight Crew Overcame Equipment Problem; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Became Reoriented; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft; Human Factors; Procedure
While climbing through FL 280 we got a cabin altitude warning horn. Cabin was at 10;000 ft and AUTO FAIL and STBY ON lights illuminated on pressurization panel. Accomplished immediate action items; [advised ATC] and the FO flew the emergency descent profile down to 9000ft. Communication with the FAs was extremely difficult during the descent. Turns out the FAs couldn't hear us or understand that we were accomplishing an emergency descent; not because O2 masks were interfering with the communication as we assumed but; rather it was because of air noise near L1 door. (We had assumed Passenger masks had deployed but learned later that they had not. I observed an amber light near pass O2 switch illuminated. It was the engine LOW IDLE light which I thought was the O2 mask light.).After arriving at 9000 ft with a more clear communication with the cabin; we learned the O2 masks had not deployed; and that the loud noise around the L1 door started shortly before we got the cabin altitude warning. I don't think the Passengers knew something was amiss until I told them they could take their masks off and we were returning to ZZZ. Returned to ZZZ below 9000 ft in MAN DC mode. Approach and landing was uneventful.After discussing event with Maintenance we discovered the aircraft has a recent history of pressurization write ups relating to the L1 door. We both reviewed the logbook prior to flight but only went back to the last airworthiness sign off. So; when the FAs mentioned the loud door noise we were not familiar with its history.
While climbing through FL280; a B737 CABIN ALTITUDE warning horn sounded along with the pressurization AUTO FAIL and STANDBY ON annunciations. An emergency descent was completed to 9;000 ft and the flight returned to the departure airport where the L1 door seal was discovered failed.