Narrative:

During climb out from ZZZ en route to ZZZ1 passing FL210; ECAM alerted crew to high cabin altitude. The cabin temperatures were very high (100+ degrees). The captain was talking to maintenance about the problem when the ECAM indicated a high cabin altitude. An immediate descent was initiated to 10000 ft and within a few seconds of starting the descent; cabin altitude was less than 10000 ft. We returned to ZZZ and landed overweight. The cabin temperature was approximately 100 degrees upon landing. One pack was on MEL and the other had a low flow insufficient to pressurize aircraft. The maintenance technician stated that the spares was short on stock and a common sensor was not available. This caused the #1 pack to be placed on MEL. The low flow of the #2 pack was not known until it operated as a single pack. Keeping common spare parts in stock and not MEL'ing packs -- especially in the summer -- would have prevented this. Had the operating pack been flow tested; the low flow would have been discovered on the ground.

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Original NASA ASRS Text

Title: DISPATCHED FROM A HOT DESERT ARPT WITH ONE PACK DEFERRED; REMAINING PACK IS UNABLE TO MAINTAIN PRESSURIZATION FOR A319.

Narrative: DURING CLBOUT FROM ZZZ ENRTE TO ZZZ1 PASSING FL210; ECAM ALERTED CREW TO HIGH CABIN ALT. THE CABIN TEMPS WERE VERY HIGH (100+ DEGS). THE CAPT WAS TALKING TO MAINT ABOUT THE PROB WHEN THE ECAM INDICATED A HIGH CABIN ALT. AN IMMEDIATE DSCNT WAS INITIATED TO 10000 FT AND WITHIN A FEW SECONDS OF STARTING THE DSCNT; CABIN ALT WAS LESS THAN 10000 FT. WE RETURNED TO ZZZ AND LANDED OVERWT. THE CABIN TEMP WAS APPROX 100 DEGS UPON LNDG. ONE PACK WAS ON MEL AND THE OTHER HAD A LOW FLOW INSUFFICIENT TO PRESSURIZE ACFT. THE MAINT TECHNICIAN STATED THAT THE SPARES WAS SHORT ON STOCK AND A COMMON SENSOR WAS NOT AVAILABLE. THIS CAUSED THE #1 PACK TO BE PLACED ON MEL. THE LOW FLOW OF THE #2 PACK WAS NOT KNOWN UNTIL IT OPERATED AS A SINGLE PACK. KEEPING COMMON SPARE PARTS IN STOCK AND NOT MEL'ING PACKS -- ESPECIALLY IN THE SUMMER -- WOULD HAVE PREVENTED THIS. HAD THE OPERATING PACK BEEN FLOW TESTED; THE LOW FLOW WOULD HAVE BEEN DISCOVERED ON THE GND.

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.