Narrative:

Cruising at FL340 just east of the intersection; we received a cabin altitude warning. We accomplished the memory items and declared an emergency with ATC. I started a descent while first officer accomplished the QRH procedure. ATC immediately cleared us to FL330 and then to FL240. First officer gained control of the cabin using manual pressurization; therefore; I expedited the descent to FL240 but did not conduct an emergency descent. The maximum altitude the cabin reached was 9800 ft. I communicated with the flight attendants and then made a PA to reassure the passenger. I then consulted with dispatch and determined that ZZZ was nearest suitable airport for a diversion. We continued at FL240 using manual pressurization techniques and landed without further incident. At ZZZ we changed aircraft and proceeded on to ZZZ1. As backgnd; the aircraft had a history of pressurization controller problems. This was our second leg with the aircraft; there were no problems on the first leg. 2 times during climb out from ZZZ2; the 'xfer lockout' and 'standby on' lights illuminated and both times the abnormal procedure returned the system to normal. We had just made logbook entry about this problem; and were discussing manual pressurization issues when the warning occurred. I would like to command the first officer for his expert and timely handling of the checklists and communications with ATC; and especially for his execution of the manual pressurization procedures. The flight attendants did a great job with the passenger. As far as I know; we followed and accomplished all procedures appropriately.

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Original NASA ASRS Text

Title: AN MD80 CREW RPTS PRESSURIZATION MALFUNCTION AT FL340; MANUAL CTL WAS GAINED AND THE FLT DIVERTED.

Narrative: CRUISING AT FL340 JUST E OF THE INTXN; WE RECEIVED A CABIN ALT WARNING. WE ACCOMPLISHED THE MEMORY ITEMS AND DECLARED AN EMER WITH ATC. I STARTED A DSCNT WHILE FO ACCOMPLISHED THE QRH PROC. ATC IMMEDIATELY CLRED US TO FL330 AND THEN TO FL240. FO GAINED CTL OF THE CABIN USING MANUAL PRESSURIZATION; THEREFORE; I EXPEDITED THE DSCNT TO FL240 BUT DID NOT CONDUCT AN EMER DSCNT. THE MAX ALT THE CABIN REACHED WAS 9800 FT. I COMMUNICATED WITH THE FLT ATTENDANTS AND THEN MADE A PA TO REASSURE THE PAX. I THEN CONSULTED WITH DISPATCH AND DETERMINED THAT ZZZ WAS NEAREST SUITABLE ARPT FOR A DIVERSION. WE CONTINUED AT FL240 USING MANUAL PRESSURIZATION TECHNIQUES AND LANDED WITHOUT FURTHER INCIDENT. AT ZZZ WE CHANGED ACFT AND PROCEEDED ON TO ZZZ1. AS BACKGND; THE ACFT HAD A HISTORY OF PRESSURIZATION CONTROLLER PROBS. THIS WAS OUR SECOND LEG WITH THE ACFT; THERE WERE NO PROBS ON THE FIRST LEG. 2 TIMES DURING CLBOUT FROM ZZZ2; THE 'XFER LOCKOUT' AND 'STANDBY ON' LIGHTS ILLUMINATED AND BOTH TIMES THE ABNORMAL PROC RETURNED THE SYS TO NORMAL. WE HAD JUST MADE LOGBOOK ENTRY ABOUT THIS PROB; AND WERE DISCUSSING MANUAL PRESSURIZATION ISSUES WHEN THE WARNING OCCURRED. I WOULD LIKE TO COMMAND THE FO FOR HIS EXPERT AND TIMELY HANDLING OF THE CHKLISTS AND COMS WITH ATC; AND ESPECIALLY FOR HIS EXECUTION OF THE MANUAL PRESSURIZATION PROCS. THE FLT ATTENDANTS DID A GREAT JOB WITH THE PAX. AS FAR AS I KNOW; WE FOLLOWED AND ACCOMPLISHED ALL PROCS APPROPRIATELY.

Data retrieved from NASA's ASRS site as of January 2009 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.