Narrative:

In cruise at FL290 cabin altitude warning horn sounded. Cabin altitude was approximately 10;000 climbing at approximately 1000 FPM. Flight crew donned o2 masked; I assumed control of aircraft; called for excessive cabin alt checklist cabin climbed to approximately 12;000 ft. I declared an emergency with ATC and began a decent to 10;000 approximately 90 miles south of ZZZ1. We went to manual dc and closed the outflow valve; the cabin began to descend. I called the a flight attendant to advise her of the problem and to enquirer if the passengers O2 masks had deployed. They had not. At this time with cabin and alt. Below 10000' I canceled the emergency with approach and landed. Outflow valve did not close in auto; pressurization system did not default to standby.

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Original NASA ASRS Text

Title: B737-300 lost automatic pressurization controller. Declared emergency and descended. Manual controller regained pressurization control.

Narrative: In cruise at FL290 cabin altitude warning horn sounded. Cabin altitude was approximately 10;000 climbing at approximately 1000 FPM. Flight crew donned o2 masked; I assumed control of aircraft; called for excessive cabin alt checklist Cabin climbed to approximately 12;000 FT. I declared an emergency with ATC and began a decent to 10;000 approximately 90 miles south of ZZZ1. We went to manual DC and closed the outflow valve; the cabin began to descend. I called the A Flight Attendant to advise her of the problem and to enquirer if the passengers O2 masks had deployed. They had not. At this time with cabin and alt. below 10000' I canceled the emergency with Approach and landed. Outflow valve did not close in auto; pressurization system did not default to standby.

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.