Narrative:

Just after leveloff at FL310, the xfer lock-out light and standby light on the pressurization control panel came on. The cabin began to climb. The red cabin altitude annunciator came on, and the horn sounded. We donned our oxygen masks, began an emergency descent, and declared an emergency. I called the flight attendants to brief them about the items saying we would be landing in dfw within 10 mins and that an evacuate/evacuation was unlikely, we were not worried about the integrity of the aircraft. I made a PA to the passenger to use their oxygen and to follow flight attendant instructions. A flight attendant then called to say the masks were not deployed so the first officer manually deployed them. During descent, I asked ATC to please notify air carrier about our divert and emergency. On downwind, once checklists were complete, I was able to notify dispatch on the radio. The first officer continued to fly and land. He did a great job and followed all procedures. The flight attendants took care of all cabin duties, calmed the passenger, and were prepared to land. Callback conversation with reporter revealed the following information: this aircraft's pressurization system, per discussion with maintenance after landing, was found to have a history of similar problems. This crew had similar indications during climb through 6000 ft but they were able to clear them through normal procedures. These indications are quite normal and, if cleared by procedure, do not require a maintenance log item. At the time of the second lockout light and standby light the cabin climb rate was 1500-2000 FPM but not considered explosive. The passenger oxygen masks were deployed manually below the cabin altitude that would have activated them automatically.

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Original NASA ASRS Text

Title: AN MD80 FLT CREW, AFTER LEVELING OFF AT FL310 IN ZFW'S AIRSPACE, EXPERIENCED DEPRESSURIZATION, CAUSING THE CAPT TO PERFORM AN EMER DSCNT AND LNDG AT THE DEST ARPT, DFW.

Narrative: JUST AFTER LEVELOFF AT FL310, THE XFER LOCK-OUT LIGHT AND STANDBY LIGHT ON THE PRESSURIZATION CTL PANEL CAME ON. THE CABIN BEGAN TO CLB. THE RED CABIN ALT ANNUNCIATOR CAME ON, AND THE HORN SOUNDED. WE DONNED OUR OXYGEN MASKS, BEGAN AN EMER DSCNT, AND DECLARED AN EMER. I CALLED THE FLT ATTENDANTS TO BRIEF THEM ABOUT THE ITEMS SAYING WE WOULD BE LNDG IN DFW WITHIN 10 MINS AND THAT AN EVAC WAS UNLIKELY, WE WERE NOT WORRIED ABOUT THE INTEGRITY OF THE ACFT. I MADE A PA TO THE PAX TO USE THEIR OXYGEN AND TO FOLLOW FLT ATTENDANT INSTRUCTIONS. A FLT ATTENDANT THEN CALLED TO SAY THE MASKS WERE NOT DEPLOYED SO THE FO MANUALLY DEPLOYED THEM. DURING DSCNT, I ASKED ATC TO PLEASE NOTIFY ACR ABOUT OUR DIVERT AND EMER. ON DOWNWIND, ONCE CHKLISTS WERE COMPLETE, I WAS ABLE TO NOTIFY DISPATCH ON THE RADIO. THE FO CONTINUED TO FLY AND LAND. HE DID A GREAT JOB AND FOLLOWED ALL PROCS. THE FLT ATTENDANTS TOOK CARE OF ALL CABIN DUTIES, CALMED THE PAX, AND WERE PREPARED TO LAND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS ACFT'S PRESSURIZATION SYS, PER DISCUSSION WITH MAINT AFTER LNDG, WAS FOUND TO HAVE A HISTORY OF SIMILAR PROBS. THIS CREW HAD SIMILAR INDICATIONS DURING CLB THROUGH 6000 FT BUT THEY WERE ABLE TO CLR THEM THROUGH NORMAL PROCS. THESE INDICATIONS ARE QUITE NORMAL AND, IF CLRED BY PROC, DO NOT REQUIRE A MAINT LOG ITEM. AT THE TIME OF THE SECOND LOCKOUT LIGHT AND STANDBY LIGHT THE CABIN CLB RATE WAS 1500-2000 FPM BUT NOT CONSIDERED EXPLOSIVE. THE PAX OXYGEN MASKS WERE DEPLOYED MANUALLY BELOW THE CABIN ALT THAT WOULD HAVE ACTIVATED THEM AUTOMATICALLY.

Data retrieved from NASA's ASRS site as of July 2007 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.