FLC IN MD80 AT FL210 LOSES PRESSURIZATION.

Narrative

DEPARTED EWR DIRECT BOS. LOST ALL PRESSURIZATION; PRESSURE CTLRS MALFUNCTIONED SIMULTANEOUSLY. SAFE DSCNT MADE TO 11000 FT. ATC ADVISED OF NATURE OF EMER. CREW AND PAX ADVISED. NO INCIDENTALS OR EMERS. MOST PAX RPTED NOT NOTICING ANYTHING UNUSUAL. MAINT DISCOVERED A FAULTY PRESSURIZATION CTLR; IT LOCKED ITSELF OUT PRIOR TO COMMUNICATING TO OUR STANDBY SYS. THIS HAS BEEN A RECURRING PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS FLYING AN MD80. HE WAS THE PF. HE DECLARED AN EMER BECAUSE THE CABIN WAS CLBING AT 2000 FPM AND ATC WAS NOT PROVIDING THE LOWER ALT. AT THE TIME OF THE 32 MIN FLT; EWR TO BOS; THEY WERE AT FL210 AND THE CABIN REACHED ABOUT 8000 FT BEFORE REGAINING CTL OF THE OUTFLOW VALVE THROUGH THE MANUAL SYS. THE RPTR WAS ABLE TO MAKE A NORMAL DSCNT SO THE PAX WERE NOT ALARMED. THE ENG AND WING ANTI-ICING HAD BEEN ON; BUT LEAKING PLUMBING WAS NOT THE PROB IN THIS CASE. THE PROB WAS A FAULTY COMPUTER IN THE PRESSURIZATION CTLR THAT LOCKED OUT THE STANDBY FUNCTION. THE MECH WENT ON TO SAY THIS PROB HAS BEEN RECURRING FREQUENTLY FOR THIS AIRLINE IN THE PAST 2 OR 3 MONTHS. THE FLT WAS ABLE TO CONTINUE ON TO ITS ORIGINAL DEST. THE RPTR STATED THAT THE NEXT TIME HE MIGHT WAIT JUST A BIT LONGER TO SEE IF THE MANUAL CLOSING OF THE OUTFLOW VALVE WOULD REGAIN PRESSURIZATION CTL; BUT HE DID NOT WANT TO DROP THE MASKS WHICH WOULD HAVE OCCURRED AUTOMATICALLY AT 14500 FT; CABIN ALT. THERE WERE NO REPERCUSSIONS RESULTING FROM THE EVENT OF DECLARING AN EMER.