B757 flight crew reported a repeat discrepancy after aircraft loss pressurization at cruise. The flight crew requested priority handling and descended. An air turn back and precautionary landing were made at departure airport.
Synopsis
B757 flight crew reported a repeat discrepancy after aircraft loss pressurization at cruise. The flight crew requested priority handling and descended. An air turn back and precautionary landing were made at departure airport.
Narrative
When we got to the aircraft there was a write up about a loud noise/vibration in the flight deck and in the Front Lav/Mid Galley from the previous flight. We delayed while maintenance worked it but they could not figure it out (it was already a repeat on that flight). We eventually got going and everything up to about 25;000 ft. was normal. At about 25;000 ft. this started again and it was deafening. The Captain and I had to scream at each other to communicate. Maintenance had asked us to try turning off the recirculation fans one at a time if this happened again so we got on with the Flight Attendants (FA) and had them listen for changes when we did that. Nothing worked and the noise/vibrations finally stopped around 28;000 ft. as it had on the previous flights.Shortly after as we leveled off at FL350 we got the Cabin Altitude Warning Light and Horn. I asked for an immediate descent and the Captain started down. We both donned our oxygen masks and reestablished communications. I coordinated for lower still and asked for a turn back to Location. ATC was fantastic and very helpful. We requested priority handling and continued down to 10;000 ft. The cabin altitude climbed up to about 12;000 ft and stayed there before coming back down. I ran the checklist and eventually had the system in manual. The passenger's oxygen mask never dropped since the cabin did not get above 14;000 ft. We flew back to Location at 10;000 ft. The rest of the approach and landing were uneventful even with the overweight landing. After landing at the gate the cabin did not depressurize so I had to do that manually.
Second reporter narrative
We arrived at aircraft to find out there was inbound write ups open regarding a vibration and loud noise. Technicians could not find a definitive cause; but suspected a recirculation fan. It was signed off and we were issued a Maintenance Release. On climb out; we received the vibration accompanied with a very loud noise that made communication in Flight Deck difficult. Noise lasted from just under 24;000 ft to 27;900 ft. Vibration remained but got slightly better when turning off the right recirculation fan (maintenance asked us to try turning off the recirculation fans in an attempt to help troubleshoot cause of the vibration and noise). Less than a minute after level off at FL350; we received a Cabin Altitude Warning and associated Horn. We followed QRC and QRH procedure and made a return to Location after an overweight landing. Maximum cabin altitude reached was 12;000 ft. No injuries with crew or passengers.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.