AN ACR MD82 FLC MADE A RAPID DSCNT WHEN THE CABIN ALT STARTED TO INCREASE.

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IN NEW YORK AIRSPACE AT FL330; EXPERIENCED CABIN CLB OF 800 FPM WITH CORRESPONDING LOSS OF DIFFERENTIAL PRESSURE BOTH PACK PRESSURES INDICATED NORMAL. FO EXECUTED RAPID DSCNT TO 10000 FT WHERE CABIN PRESSURE RETURNED TO NORMAL. CONTINUED TO BOS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAPT SAID THAT THEY HAD REVIEWED THE MD82'S MAINT LOG AND NOTED A PREVIOUS WRITE-UP ABOUT LOW AIR FLOW FROM THE R PACK. INITIALLY; THE PACK WORKED NORMALLY; BUT JUST AS THEY WERE PREPARING FOR DSCNT THEY NOTED THAT THE AIR CONDITIONING AND PRESSURIZATION FLOW LIGHT WAS ILLUMINATED AND THE CABIN ALT GAUGE WAS INDICATING AN INCREASE IN ALT OF 800 FPM. THE FLC REQUESTED A LOWER ALT AND TOLD THE CTLR THAT THEY WERE HAVING A PRESSURIZATION PROB AND THAT THEY NEEDED TO GET TO 10000 FT WHEN HE COULD ACCOMMODATE THEM. THE CAPT SAID THAT AT NO TIME DID HE FEEL THAT THE CABIN ALT WAS GOING TO INCREASE TO THE POINT THAT THE WARNING SYS WERE GOING TO SOUND OR THE MASKS DEPLOY. AFTER ARRIVING AT 10000 FT; THE REST OF THE FLT WAS NORMAL AND MAINT PERSONNEL WERE WAITING WHEN THEY PARKED AT THE GATE.