Narrative:

Due to loss of an air-conditioning pack (caused by failure of automatic temperature control) 1 pack remaining did not have enough pressure to hold cabin altitude. As cabin pressure hit 9000 ft and after 3 attempts to call ATC to no avail, I began an emergency descent to a lower altitude, and set transponder to 7700. At about FL320 (originally at FL330) controller came on frequency and we asked for FL290, as pressure stabilized below 9000 ft. At FL290 cabin altitude remained controlable so emergency was terminated. No clearance conflicts were evident or noted by ATC who said he had been on 'landline.'

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Original NASA ASRS Text

Title: A DC9-30 IN CRUISE AT FL330 DECLARED AN EMER AND DSNDED DUE TO UNABLE TO MAINTAIN CABIN PRESSURE CAUSED BY THE L AIR-CONDITIONING PACK FAILURE.

Narrative: DUE TO LOSS OF AN AIR-CONDITIONING PACK (CAUSED BY FAILURE OF AUTO TEMP CTL) 1 PACK REMAINING DID NOT HAVE ENOUGH PRESSURE TO HOLD CABIN ALT. AS CABIN PRESSURE HIT 9000 FT AND AFTER 3 ATTEMPTS TO CALL ATC TO NO AVAIL, I BEGAN AN EMER DSCNT TO A LOWER ALT, AND SET XPONDER TO 7700. AT ABOUT FL320 (ORIGINALLY AT FL330) CTLR CAME ON FREQ AND WE ASKED FOR FL290, AS PRESSURE STABILIZED BELOW 9000 FT. AT FL290 CABIN ALT REMAINED CONTROLABLE SO EMER WAS TERMINATED. NO CLRNC CONFLICTS WERE EVIDENT OR NOTED BY ATC WHO SAID HE HAD BEEN ON 'LANDLINE.'

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.