Narrative:

At cruise altitude of FL320 the copilot noticed that the flow light had illuminated. As the copilot was initiating the flow light checklist; I noticed that the cabin climb indicator was pegged at above 1500/FPM climb rate; and cabin altitude was climbing. We received clearance to descend but had no inoperative lights illuminated on the pressurization panel. The right and left pneumatic supply pressure appeared to be normal. As I continued our descent; the copilot started to initiate the automatic pressurization inoperative/manual pressurization checklist. The copilot selected automatic #2 at approximately FL310 and the cabin rate of climb decreased with a momentary bump and the flow light extinguished; but then the cabin climb rate quickly increased again to greater than 1500/FPM. As we continued our descent it became apparent that the cabin altitude was out of control at which time the copilot initiated the rapid decompressions/cabin altitude warning checklist as I initiated an emergency descent. We donned our oxygen masks and at 10000 ft cabin altitude the red cabin altitude light illuminated and the warning horn/vocal sounded. The cabin altitude appeared to go above 14000 ft momentarily but the passenger oxygen masks did not deploy and since the cabin altitude was rapidly descending with the aircraft's altitude toward 9000 ft I elected not to manually deploy the passenger oxygen masks. During all this I was coordinating with the flight attendants who stated that none of the passenger seemed to notice the descent nor did anyone complain about the pressurization. The only apparently noticeable event was that the rear galley door was making a slightly loud noise during descent. All of the dscnts were coordination with ATC who was able to keep our clrncs below our desired altitude until we reached 11000 ft where a momentary delay was encountered. At this time I declared an emergency and received an immediate clearance to 9000 ft. At no time was it necessary to violate any ATC clrncs. The copilot was starting to make some progress with the manual control of the pressurization but he stated that it was difficult to move the cabin control wheel and was unable to get the position indicator beyond the flaps 28 degree setting. At this time we were initiating our leveloff and I asked the copilot to discontinue his attempts to regain control of the cabin manually. After landing; I made a PA notifying the passenger that our aircraft had encountered some pressurization difficulties and apologized for any discomfort. No passenger said anything to me concerning the pressurization except for one lady near the very rear of the airplane who said she was having some difficulty clearing her right ear.

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Original NASA ASRS Text

Title: AN MD80 LOW FLOW LIGHT ILLUMINATED AT FL320. AN EMER DSCNT WAS COMPLETED BECAUSE THE CABIN COULD NOT BE CONTROLLED. THE PAX O2 MASKS DID NOT DEPLOY.

Narrative: AT CRUISE ALT OF FL320 THE COPLT NOTICED THAT THE FLOW LIGHT HAD ILLUMINATED. AS THE COPLT WAS INITIATING THE FLOW LIGHT CHKLIST; I NOTICED THAT THE CABIN CLB INDICATOR WAS PEGGED AT ABOVE 1500/FPM CLB RATE; AND CABIN ALT WAS CLBING. WE RECEIVED CLRNC TO DSND BUT HAD NO INOP LIGHTS ILLUMINATED ON THE PRESSURIZATION PANEL. THE R AND L PNEUMATIC SUPPLY PRESSURE APPEARED TO BE NORMAL. AS I CONTINUED OUR DSCNT; THE COPLT STARTED TO INITIATE THE AUTO PRESSURIZATION INOP/MANUAL PRESSURIZATION CHKLIST. THE COPLT SELECTED AUTO #2 AT APPROX FL310 AND THE CABIN RATE OF CLB DECREASED WITH A MOMENTARY BUMP AND THE FLOW LIGHT EXTINGUISHED; BUT THEN THE CABIN CLB RATE QUICKLY INCREASED AGAIN TO GREATER THAN 1500/FPM. AS WE CONTINUED OUR DSCNT IT BECAME APPARENT THAT THE CABIN ALT WAS OUT OF CTL AT WHICH TIME THE COPLT INITIATED THE RAPID DECOMPRESSIONS/CABIN ALT WARNING CHKLIST AS I INITIATED AN EMER DSCNT. WE DONNED OUR OXYGEN MASKS AND AT 10000 FT CABIN ALT THE RED CABIN ALT LIGHT ILLUMINATED AND THE WARNING HORN/VOCAL SOUNDED. THE CABIN ALT APPEARED TO GO ABOVE 14000 FT MOMENTARILY BUT THE PAX OXYGEN MASKS DID NOT DEPLOY AND SINCE THE CABIN ALT WAS RAPIDLY DSNDING WITH THE ACFT'S ALT TOWARD 9000 FT I ELECTED NOT TO MANUALLY DEPLOY THE PAX OXYGEN MASKS. DURING ALL THIS I WAS COORDINATING WITH THE FLT ATTENDANTS WHO STATED THAT NONE OF THE PAX SEEMED TO NOTICE THE DSCNT NOR DID ANYONE COMPLAIN ABOUT THE PRESSURIZATION. THE ONLY APPARENTLY NOTICEABLE EVENT WAS THAT THE REAR GALLEY DOOR WAS MAKING A SLIGHTLY LOUD NOISE DURING DSCNT. ALL OF THE DSCNTS WERE COORD WITH ATC WHO WAS ABLE TO KEEP OUR CLRNCS BELOW OUR DESIRED ALT UNTIL WE REACHED 11000 FT WHERE A MOMENTARY DELAY WAS ENCOUNTERED. AT THIS TIME I DECLARED AN EMER AND RECEIVED AN IMMEDIATE CLRNC TO 9000 FT. AT NO TIME WAS IT NECESSARY TO VIOLATE ANY ATC CLRNCS. THE COPLT WAS STARTING TO MAKE SOME PROGRESS WITH THE MANUAL CTL OF THE PRESSURIZATION BUT HE STATED THAT IT WAS DIFFICULT TO MOVE THE CABIN CTL WHEEL AND WAS UNABLE TO GET THE POS INDICATOR BEYOND THE FLAPS 28 DEG SETTING. AT THIS TIME WE WERE INITIATING OUR LEVELOFF AND I ASKED THE COPLT TO DISCONTINUE HIS ATTEMPTS TO REGAIN CTL OF THE CABIN MANUALLY. AFTER LNDG; I MADE A PA NOTIFYING THE PAX THAT OUR ACFT HAD ENCOUNTERED SOME PRESSURIZATION DIFFICULTIES AND APOLOGIZED FOR ANY DISCOMFORT. NO PAX SAID ANYTHING TO ME CONCERNING THE PRESSURIZATION EXCEPT FOR ONE LADY NEAR THE VERY REAR OF THE AIRPLANE WHO SAID SHE WAS HAVING SOME DIFFICULTY CLRING HER R EAR.

Data retrieved from NASA's ASRS site as of May 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.