Narrative:

Stablized cruise altitude FL370, the first officer and I both felt a large pressure surge on our ears, momentarily thereafter the master caution 'air conditioning' annuciator light came on. The 'automatic fail' and 'stand by lights' on pressure controller were illuminated. Cabin altitude was above 10000 ft. Rate of change 3000 FPM plus, and the cabin altitude horn was on. The first officer and I donned our oxygen mask, established communications, and selected stand by on the pressure controller. The cabin continued to climb at which point we selected manual, noting that the outflow value was closed. We also made note of the fact that there were no indications of any door lights being open, and that both packs and bleeds were on with no apparent malfunctions. At this time I made the decision to execute an emergency descent. We notified the atl center of our problem, and that we had begun the descent requesting a turn off the arwy. The start switches were placed to flight, the seatbelt sign was turned on, and a brief PA announcement was made to alert both passengers and F/as. I also requested the first officer to accomplish the emergency descent checklist. Somewhere during the descent, the pressure controller (still on manual) apparently drove the cabin down to 8000 ft and descending. We stopped the descent at FL190, but shortly thereafter the cabin began to climb at a high rate (1000 FPM) with the outflow valve closed. Because of this erratic behavior of the controller, we continued the descent to 9000 ft and proceeded to billings. We selected billings due to our near proximity, and the availability of medical personnel to see to our possibly injured passengers. During this period of time paramedics/ medical assistance was requested, as our communication with the F/as related numerous people with ear problems, and several with near hysteria. Upon arrival, 13 people plus 2 infants and I F/a proceeded to area hospitals for chkup. My current understanding is that none were admitted. I feel that the pressurization problem appears to have been partial and temporary probably caused initially by the pressure controller itself. I have no suggestions to prevent a recurrence as it was probably an isolated occurrence.

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Original NASA ASRS Text

Title: FLT CREW OF ACR MLG ENCOUNTERS PROBLEMS WITH THE ACFT PRESSURE CTLR AND EXECUTES AN EMERGENCY DESCENT AND LNDG. SOME PASSENGERS TREATED FOR EAR PROBLEMS.

Narrative: STABLIZED CRUISE ALT FL370, THE F/O AND I BOTH FELT A LARGE PRESSURE SURGE ON OUR EARS, MOMENTARILY THEREAFTER THE MASTER CAUTION 'AIR CONDITIONING' ANNUCIATOR LIGHT CAME ON. THE 'AUTO FAIL' AND 'STAND BY LIGHTS' ON PRESSURE CTLR WERE ILLUMINATED. CABIN ALT WAS ABOVE 10000 FT. RATE OF CHANGE 3000 FPM PLUS, AND THE CABIN ALT HORN WAS ON. THE F/O AND I DONNED OUR OXYGEN MASK, ESTABLISHED COMS, AND SELECTED STAND BY ON THE PRESSURE CTLR. THE CABIN CONTINUED TO CLB AT WHICH POINT WE SELECTED MANUAL, NOTING THAT THE OUTFLOW VALUE WAS CLOSED. WE ALSO MADE NOTE OF THE FACT THAT THERE WERE NO INDICATIONS OF ANY DOOR LIGHTS BEING OPEN, AND THAT BOTH PACKS AND BLEEDS WERE ON WITH NO APPARENT MALFUNCTIONS. AT THIS TIME I MADE THE DECISION TO EXECUTE AN EMER DSCNT. WE NOTIFIED THE ATL CTR OF OUR PROB, AND THAT WE HAD BEGUN THE DSCNT REQUESTING A TURN OFF THE ARWY. THE START SWITCHES WERE PLACED TO FLT, THE SEATBELT SIGN WAS TURNED ON, AND A BRIEF PA ANNOUNCEMENT WAS MADE TO ALERT BOTH PAXS AND F/AS. I ALSO REQUESTED THE F/O TO ACCOMPLISH THE EMER DSCNT CHKLIST. SOMEWHERE DURING THE DSCNT, THE PRESSURE CTLR (STILL ON MANUAL) APPARENTLY DROVE THE CABIN DOWN TO 8000 FT AND DSNDING. WE STOPPED THE DSCNT AT FL190, BUT SHORTLY THEREAFTER THE CABIN BEGAN TO CLB AT A HIGH RATE (1000 FPM) WITH THE OUTFLOW VALVE CLOSED. BECAUSE OF THIS ERRATIC BEHAVIOR OF THE CTLR, WE CONTINUED THE DSCNT TO 9000 FT AND PROCEEDED TO BILLINGS. WE SELECTED BILLINGS DUE TO OUR NEAR PROX, AND THE AVAILABILITY OF MEDICAL PERSONNEL TO SEE TO OUR POSSIBLY INJURED PAXS. DURING THIS PERIOD OF TIME PARAMEDICS/ MEDICAL ASSISTANCE WAS REQUESTED, AS OUR COM WITH THE F/AS RELATED NUMEROUS PEOPLE WITH EAR PROBS, AND SEVERAL WITH NEAR HYSTERIA. UPON ARR, 13 PEOPLE PLUS 2 INFANTS AND I F/A PROCEEDED TO AREA HOSPITALS FOR CHKUP. MY CURRENT UNDERSTANDING IS THAT NONE WERE ADMITTED. I FEEL THAT THE PRESSURIZATION PROB APPEARS TO HAVE BEEN PARTIAL AND TEMPORARY PROBABLY CAUSED INITIALLY BY THE PRESSURE CTLR ITSELF. I HAVE NO SUGGESTIONS TO PREVENT A RECURRENCE AS IT WAS PROBABLY AN ISOLATED OCCURRENCE.

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.