Narrative:

Aircraft had experienced pressurization system failure (analog system) previous day. Maintenance had spent the night working the problem. Our flight originated; full of passengers; with three maintenance employees--two on flight deck jump seats. I briefed flight attendants about previous problem so they were aware of pressurization problem history. Started taxi and had normal takeoff. Climb on course; cleared to cruise altitude of FL310. Climb checklist showed cabin pressure normal. Climbing through about FL220; about 1500 fpm; one maintenance employee leaned forward; pointed at the cabin pressure gauge and said; 'it's getting close to 10;000 ft.' we looked and several seconds later; the cabin altitude warning horn sounded. I called for masks and descent. All four donned masks and communications established. We started descent. I set start switches to flight and checked cabin altitude again (about 11;500' where it topped out) and passenger oxygen panel (not deployed). [We] decided not to activate the system at that point; also decided not to squawk 7700. ATC frequency was congested; but shortly after starting descent; I was able to call with pressure failure and request for descent to 10;000'. Center immediately cleared us to 10;000'. There were no TCAS alerts or separation problems that I am aware of. I pulled out the QRH and reviewed actions taken with both checklists. I looked for the outflow valve procedure; knowing it had to be closed; but couldn't find it right away (I looked in wrong place.) bleed switch positions were not the problem. Spent a moment looking at that verbiage. Maintenance employee then suggested we select 'manual' on pressurization panel and close the valve. Valve was indicating about 1/4 open (mostly closed). I went manual dc and closed valve to achieve about 1000 fpm cabin descent rate; noted cabin at about 10;000 ft as aircraft passed 16;000 ft. I requested 9000 ft level-off altitude and a turn back to [departure airport]; which was granted. (I chose 9000 ft as it didn't look like the pressure controller would return cabin pressure to normal levels; and I wanted it to be lower than 10;000 ft.) spoke with flight attendants during descent; checked cabin and passenger status; and; once level and returning; advised passengers. Completed QRH procedures and landed normally. If I had it to do over again; I'd do two things differently. First; [I would] squawk 7700; to get ATC's attention. I would have done so if not able to talk to ATC right away. I did not declare an emergency (I should have); but we were given the same traffic priority handling as though we had. Second; I would have more carefully followed the QRH checklist. If I had; I'd have found the outflow valve closing procedure in the warning horn portion of the page; and not gotten lost in the bleed switch procedure lower on the page. In other words; checklist discipline; use it as intended; one step at a time; from the top. Two things worked against us here: maintenance inputs from the jump seats and my having taken or assured many of the immediate actions for the pressure problem and emergency descent were accomplished from memory. Extra resources on the flight deck; especially authoritative ones; are good; but have to be managed. And; though we handled the problem well by smoothly transitioning to a descent and stopping cabin altitude climb at 11;500 ft (no physiological problems were reported). I could have gotten the outflow valve closed sooner; if I'd followed the QRH properly; rather than skipping around!

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Original NASA ASRS Text

Title: A B737 Flight Crew reported loss of pressurization in climb. They executed a descent; regained control of cabin pressure; and chose to return to departure airport.

Narrative: Aircraft had experienced pressurization system failure (analog system) previous day. Maintenance had spent the night working the problem. Our flight originated; full of passengers; with three Maintenance Employees--two on flight deck jump seats. I briefed Flight Attendants about previous problem so they were aware of pressurization problem history. Started taxi and had normal takeoff. Climb on course; cleared to cruise altitude of FL310. Climb checklist showed cabin pressure normal. Climbing through about FL220; about 1500 fpm; one Maintenance Employee leaned forward; pointed at the cabin pressure gauge and said; 'It's getting close to 10;000 ft.' We looked and several seconds later; the Cabin Altitude Warning horn sounded. I called for masks and descent. All four donned masks and communications established. We started descent. I set start switches to FLT and checked cabin altitude again (about 11;500' where it topped out) and passenger oxygen panel (not deployed). [We] decided not to activate the system at that point; also decided not to squawk 7700. ATC frequency was congested; but shortly after starting descent; I was able to call with pressure failure and request for descent to 10;000'. Center immediately cleared us to 10;000'. There were no TCAS alerts or separation problems that I am aware of. I pulled out the QRH and reviewed actions taken with both checklists. I looked for the outflow valve procedure; knowing it had to be closed; but couldn't find it right away (I looked in wrong place.) Bleed switch positions were not the problem. Spent a moment looking at that verbiage. Maintenance Employee then suggested we select 'Manual' on pressurization panel and close the valve. Valve was indicating about 1/4 open (mostly closed). I went Manual DC and closed valve to achieve about 1000 fpm cabin descent rate; noted cabin at about 10;000 ft as aircraft passed 16;000 ft. I requested 9000 ft level-off altitude and a turn back to [departure airport]; which was granted. (I chose 9000 ft as it didn't look like the pressure controller would return cabin pressure to normal levels; and I wanted it to be lower than 10;000 ft.) Spoke with Flight Attendants during descent; checked cabin and passenger status; and; once level and returning; advised passengers. Completed QRH procedures and landed normally. If I had it to do over again; I'd do two things differently. First; [I would] squawk 7700; to get ATC's attention. I would have done so if not able to talk to ATC right away. I did not declare an emergency (I should have); but we were given the same traffic priority handling as though we had. Second; I would have more carefully followed the QRH checklist. If I had; I'd have found the outflow valve closing procedure in the warning horn portion of the page; and not gotten lost in the bleed switch procedure lower on the page. In other words; checklist discipline; use it as intended; one step at a time; from the top. Two things worked against us here: Maintenance inputs from the jump seats and my having taken or assured many of the immediate actions for the pressure problem and emergency descent were accomplished from memory. Extra resources on the flight deck; especially authoritative ones; are good; but have to be managed. And; though we handled the problem well by smoothly transitioning to a descent and stopping cabin altitude climb at 11;500 ft (no physiological problems were reported). I could have gotten the outflow valve closed sooner; if I'd followed the QRH properly; rather than skipping around!

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.