MD80 CREW LOST CTL OF CABIN PRESSURIZATION AND WAS REQUIRED TO MAKE AN EMER DSCNT TO 10000 FT.

Narrative

A LARGE STORM SYS WAS ON THE RADAR AND HAD BEEN RPTED FROM JUST E OF AMA; REACHING NE TO ABOUT ICT. TOPS TO 5500 FT. WE WERE IN THE CLR; BUT AS WE APCHED WITHIN 30 NM N OF THE WESTERN MOST STORMS; WE TURNED 30 DEGS R 240-250 DEG HDG IN ORDER TO STAY N AND W OF THE WX. AT THIS POINT; WE ENTERED CLOUDS; STARTED PICKING UP LIGHT TO MODERATE CHOP AND TURB. AFTER 10-15 MINS; WE NOTICED ICE BEGINNING TO BUILD UP AND GETTING WORSE. I TURNED AN ADDITIONAL 20 DEGS R IN HOPES THAT WE WOULD MORE RAPIDLY EXIT THE WX. 5-10 MINS LATER; JUST N OF AMA; WE DID EXIT INTO CLR AIR AND DEICED THE TAIL FOR A SECOND TIME TO CLEAN OFF REMAINING STRUCTURAL ICE. WITHIN 5 MINS OF THIS; OUR ATTN WAS DRAWN TO THE ANNUNCIATOR PANEL BY AN AMBER PRESSURIZATION FLOW LIGHT. THE CABIN PRESSURE WAS INCREASING BY 600-70 FT AND THE CABIN WAS ALREADY ABOVE 9000 FT AND RISING. PRESSURE ON L-HAND PACK WAS 27 PSI; R-HAND PACK WAS 25 PSI. INITIAL REACTION WAS TO ADJUST TEMP HIGHER IN HOPES OF ADDING MORE AIR AND PERHAPS UNFREEZING POTENTIALLY FROZEN VALVES. THIS DID NOT SOLVE THE PROB; SO WE REQUESTED AND RECEIVED CLRNC TO DSND TO FL250. WE ALSO IMMEDIATELY PROCEEDED WITH RAPID DECOMPRESSION CHKLIST. MANUALLY CLOSING THE OUTFLOW VALVE DID NOT IMMEDIATELY ARREST THE CABIN'S CLB. AS WE DSNDED; THE CABIN HIT 10000 FT AND THE RED CABIN PRESSURE LIGHT CAME ON. AT THIS POINT; I DECLARED EMER AND RECEIVED CLRNC TO 10000 FT. WE COMPLETED EXPLOSIVE DECOMPRESSION CHKLIST. I ELECTED NOT TO HAVE THE FO EJECT THE PAX OXYGEN MASKS BECAUSE I NEEDED HIM TO HELP ME COMPLETE OTHER DUTIES WITH THE ACFT AND WE WERE HAVING SOME PROBS WITH THE INTERCOCKPIT COM. THE PAX MASKS NEVER DROPPED; PROBABLY BECAUSE AT SOME POINT BEFORE 10000 FT; THE OUTFLOW VALVE DROVE FULL CLOSED AND THE CABIN REPRESSURIZED. IN FACT; THAT WAS MY LESSON LEARNED. WE WERE SO BUSY WITH THE ACFT CTL AND COM THAT THE CABIN PRESSURE DROVE TO ZERO BY THE TIME WE LEVELED AT 10000 FT AND WE NOTICED IT. WE RE-ESTABLISHED AUTOPRESSURE CTL AND THAT WORKED INTO ELP. 2 PAX RECEIVED MEDICAL ATTN AT THE GATE FOR BLOCKED SINUS AND EARS. THE PAX WERE OK AFTER EMS ATTENDED TO THEM.