B727-200 EXPERIENCES LOSS OF PRESSURIZATION ON CLBOUT.

Narrative

CLBING THROUGH FL290; I ALERTED THE CAPT THAT THE CABIN ALT WAS CLBING THROUGH 9000-9500 FT. THE CAPT AND I BEGAN RUNNING COM PROC; UNSCHEDULED CABIN PRESSURE CHANGE; WHILE FO CONTINUED TO FLY THE ACFT. WE WERE UNABLE TO CTL THE CABIN USING THIS PROC. WHEN THE ALT REACHED 10000 FT; THE CABIN WARNING HORN SOUNDED. WE IMMEDIATELY PLACED OUR OXYGEN MASKS ON AND SHORTLY AFTER; THE CAPT DECLARED AN EMER WITH CTR. FO BEGAN AN EMER DSCNT AND I ACCOMPLISHED THE RAPID DSCNT CHKLIST. CTR GAVE US AN IMMEDIATE VECTOR BACK TO ZZZ AND CLRED US TO 11000 FT. DURING OUR DSCNT; THE CABIN ALT REACHED 14000 FT AND THE CABIN OXYGEN MASKS WERE DEPLOYED. AFTER DSNDING THROUGH 12000 FT; THE CAPT MADE A PA TO THE PAX THAT IT WAS NOW SAFE TO DISCONTINUE THE USE OF OXYGEN. AFTER DSNDING TO 10000 FT; THE CREW TERMINATED THE USE OF OXYGEN. THE CAPT CALLED THE LEAD FLT ATTENDANT INTO THE FLT DECK AND BRIEFED HER ON THE SITUATION. WE DUMPED APPROX 12000 LBS OF FUEL AND COMMUNICATED WITH DISPATCH AND MAINT CTL ADVISING THEM OF OUR SITUATION. THE FLT CONTINUED TO ZZZ AND LANDED UNEVENTFULLY.