Narrative:

While at cruise flight at FL360; the cabin altitude warning horn sounded. We immediately donned our oxygen masks and established crew communications. I was the pilot monitoring. I noticed the cabin altitude at 10;500 feet and saw the cabin altitude rising at what looked like 500 FPM. I pulled out the QRH and referenced the appropriate checklist. We accomplished the required memory items; started a descent; and while in the process of running the checklist; we regained control of the cabin pressure. I was aware of another depressurization event and I elected to divert. During this event; I directed a descent to a lower altitude before completing all QRH procedures in the stated order. My concern at this time was descending to a lower altitude due to the previous day's event that had a pressurization issue. I confirmed the engine bleed switches on and then moved both pack switches from auto to high. This did not seem to have any effect on the rising cabin pressure. It was at this time that I contacted center and told them that we were having pressurization issues and were requesting lower with a turn back towards the departure airport. I did not accomplish the checklist procedures calling for switching the pressurization control to manual and then manually controlling the outflow valve prior to contacting center. As I was returning to the QRH to insure we had complied with all steps; the cabin pressure came under control and we did not continue with the QRH procedures. After landing; I spoke with the mechanic about the pressurization issue. The mechanic said this aircraft had previous problems with pressurization. When we showed up to our originating flight; we were told that all aircraft had undergone inspections in light of other depressurization events. There was no annotation in the logbook regarding any inspections so I called dispatch and told them I had heard of the inspection requirement but could not find anything stating the inspection had been accomplished. Dispatch said they would call maintenance and get back with me. Just prior to push; I re-contacted dispatch and they told me that there would not be anything in the logbook but company aircraft had been inspected and that we were good to go. This situation impacted my decision to immediately start a descent with a pressurization issue prior to completing all checklist procedures. Since the cabin pressurization came under control during descent; I had no need to accomplish the steps previously omitted. I feel that the lack of documentation concerning the aircraft inspection had an effect on my decision to start down so quickly.

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Original NASA ASRS Text

Title: A B737 crew conducted an emergency descent after the cabin altitude exceeded 10;000 FT and the cabin altitude warning sounded. Cabin altitude control was regained during the descent.

Narrative: While at cruise flight at FL360; the cabin altitude warning horn sounded. We immediately donned our oxygen masks and established Crew communications. I was the Pilot Monitoring. I noticed the cabin altitude at 10;500 feet and saw the cabin altitude rising at what looked like 500 FPM. I pulled out the QRH and referenced the appropriate checklist. We accomplished the required memory items; started a descent; and while in the process of running the checklist; we regained control of the cabin pressure. I was aware of another depressurization event and I elected to divert. During this event; I directed a descent to a lower altitude before completing all QRH procedures in the stated order. My concern at this time was descending to a lower altitude due to the previous day's event that had a pressurization issue. I confirmed the engine bleed switches on and then moved both pack switches from auto to high. This did not seem to have any effect on the rising cabin pressure. It was at this time that I contacted Center and told them that we were having pressurization issues and were requesting lower with a turn back towards the departure airport. I did not accomplish the checklist procedures calling for switching the pressurization control to manual and then manually controlling the outflow valve prior to contacting Center. As I was returning to the QRH to insure we had complied with all steps; the cabin pressure came under control and we did not continue with the QRH procedures. After landing; I spoke with the Mechanic about the pressurization issue. The Mechanic said this aircraft had previous problems with pressurization. When we showed up to our originating flight; we were told that all aircraft had undergone inspections in light of other depressurization events. There was no annotation in the logbook regarding any inspections so I called Dispatch and told them I had heard of the inspection requirement but could not find anything stating the inspection had been accomplished. Dispatch said they would call maintenance and get back with me. Just prior to push; I re-contacted Dispatch and they told me that there would not be anything in the logbook but Company aircraft had been inspected and that we were good to go. This situation impacted my decision to immediately start a descent with a pressurization issue prior to completing all checklist procedures. Since the cabin pressurization came under control during descent; I had no need to accomplish the steps previously omitted. I feel that the lack of documentation concerning the aircraft inspection had an effect on my decision to start down so quickly.

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.