After experiencing an uncontrollable increase in cabin altitude; an md-82 flight crew declared an em...

Narrative:

After leveling off at FL310 the 'cabin altitude' light illuminated and the aural warning sounded. [We] accomplished the immediate action items of 'cabin altitude warning/rapid depressurization' checklist. Cabin altitude was over 10;000 ft and initially did not appear to be decreasing. Declared emergency and started emergency descent. During descent to 10;000 ft verified that cabin was not exceeding 14;000 ft. We did not deploy the cabin oxygen masks and they did not automatically deploy as cabin altitude remained less than 14;000 ft. Returned to our departure airport and accomplished an uneventful overweight landing. [It] appears that the automatic pressurization system failed.

Original NASA ASRS Text

Title: After experiencing an uncontrollable increase in cabin altitude; an MD-82 flight crew declared an emergency; performed an emergency descent to 10;000 MSL and returned to their departure airport where they completed an overweight but uneventful landing.

Narrative: After leveling off at FL310 the 'cabin altitude' light illuminated and the aural warning sounded. [We] accomplished the immediate action items of 'Cabin Altitude Warning/Rapid Depressurization' checklist. Cabin altitude was over 10;000 FT and initially did not appear to be decreasing. Declared emergency and started emergency descent. During descent to 10;000 FT verified that cabin was not exceeding 14;000 FT. We did not deploy the cabin oxygen masks and they did not automatically deploy as cabin altitude remained less than 14;000 FT. Returned to our departure airport and accomplished an uneventful overweight landing. [It] appears that the automatic pressurization system failed.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1101293
Time
Date	201307
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Aircraft 1
Make Model Name	MD-82
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Pressurization System
Person 1
Function	First Officer Pilot Not Flying
Person 2
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

After experiencing an uncontrollable increase in cabin altitude; an md-82 flight crew declared an emergency; performed an emergency descent to 10;000 MSL and returned to their departure airport where they completed an overweight but uneventful landing.