B737 flight crew is advised during climb by the A Flight Attendant that the forward cabin door has a loud hiss. Approaching FL290 the crew requests a level off then a descent when the cabin continues to climb. The cabin altitude warning horn sounds as descent is commenced and the flight returns to departure airport.
Synopsis
B737 flight crew is advised during climb by the A Flight Attendant that the forward cabin door has a loud hiss. Approaching FL290 the crew requests a level off then a descent when the cabin continues to climb. The cabin altitude warning horn sounds as descent is commenced and the flight returns to departure airport.
Narrative
On departure climb out; we received a call from our A Flight Attendant. She indicated that she was hearing a loud hiss from the forward entrance door after the ten thousand foot ding. We elected to continue our climb as the pressurization seemed relatively normal at this point; and we hoped the door seal would seal itself as the cabin PSI increased. I asked the A to call us back if the hiss continued. ATC continued our climb clearances to our cruise altitude. Our A called back and said the loud hiss continued. We leveled off at FL290 to check cabin rate. The cabin was climbing at 900 to 1000 ft per min. We notified ATC that we had a pressurization problem and need lower quickly and we planned to return. We received initial clearance to 17;000' and then later to 13;000'. We descended at max rate. Our cabin altitude warning went off; we did our memory items; donned our O2 masks and turned back toward ZZZ airport. We declined to declare an emergency as our descent clearance came quickly and our cabin altitude never climbed above 11;000 ft; with 6 psi of pressure. At this point we went direct to the field and were given further step down altitudes as terrain allowed. We landed without further incident.
Second reporter narrative
At 10;000 ft; the Flight Attendant in the front called up and said the door was very loud and Passengers were complaining. I could hear it through the intercom and it sounded like the door seal was not properly seated. We continued to climb and monitored the cabin pressure thinking the seal would be closed as the pressure in the cabin increased. The cabin pressure gauge showed a 6 psi pressure difference. However; the cabin was climbing at just under 1;000 ft per minute.We called ATC and asked for a level off; which we were given at Fl290. After we leveled; the cabin continued to climb; and we notified ATC that we needed to return. He gave us vectors; and as he was; we got the cabin altitude warning horn. We performed the memory items and I pulled out the checklist while the Captain started a decent; which we were given by ATC to 17;000 ft. At the time this was as low as we could get due to terrain. I did the checklist while the Captain flew; and by the time I got the Emergency Decent checklist; we were given clearance to 13;000 ft; and we continued down to that altitude. At this point we were direct to the field and given a few more step-downs until we reached 10;000 ft.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.