Narrative:

The B727 has 2 pressurization units called 'packs.' one was inoperative, and it was MEL'ed. When one pack is inoperative, you are restr to FL250 or below. We were cruising at FL250. The aircraft would not maintain pressurization. Cabin altitude was climbing to 9500 ft. We descended to FL220 to see if the lower altitude would help. We then tried FL180, only we could not maintain a cabin altitude to below 10000 ft. We requested a descent to 10000 ft MSL. The controller cleared us to 11000 ft. We descended to 10000 ft when cleared by ATC. We never had to stop the descent to 10000 ft. We had to dump 3500 pounds of jet-a fuel around the tulie VOR near bakersfield. We returned to lax at 9000 ft, landed with no further problems.

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Original NASA ASRS Text

Title: A B727-200 AT FL250 DSNDED TO 11000 FT AND DIVERTED DUE TO FAILURE TO MAINTAIN CABIN PRESSURE CAUSED BY A FAILED MAIN CARGO DOOR SEAL.

Narrative: THE B727 HAS 2 PRESSURIZATION UNITS CALLED 'PACKS.' ONE WAS INOP, AND IT WAS MEL'ED. WHEN ONE PACK IS INOP, YOU ARE RESTR TO FL250 OR BELOW. WE WERE CRUISING AT FL250. THE ACFT WOULD NOT MAINTAIN PRESSURIZATION. CABIN ALT WAS CLBING TO 9500 FT. WE DSNDED TO FL220 TO SEE IF THE LOWER ALT WOULD HELP. WE THEN TRIED FL180, ONLY WE COULD NOT MAINTAIN A CABIN ALT TO BELOW 10000 FT. WE REQUESTED A DSCNT TO 10000 FT MSL. THE CTLR CLRED US TO 11000 FT. WE DSNDED TO 10000 FT WHEN CLRED BY ATC. WE NEVER HAD TO STOP THE DSCNT TO 10000 FT. WE HAD TO DUMP 3500 LBS OF JET-A FUEL AROUND THE TULIE VOR NEAR BAKERSFIELD. WE RETURNED TO LAX AT 9000 FT, LANDED WITH NO FURTHER PROBS.

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.