Narrative:

On this particular flight, we experienced a pressurization problem which is neither addressed in company nor manufacturer's manuals. At 10000 ft MSL, the automatic system failed and our flight engineer switched to the standby system. Climbing through 18000 ft MSL, the entire pressurization system failed (automatic, standby, manual AC/dc) and the outflow valve failed in the closed position which caused the pressurization system to climb to the 9.6 psi relief valve limit in a short time span. The captain elected not to troubleshoot further and land immediately at dfw. On descent, the cabin remained at 9.6 psi differential. On landing the squat switch on the main gear opened the outflow valve and we experienced a rapid decompression which filled the aircraft with a cloud of moisture for 5-10 seconds which quickly dissipated. Fortunately nobody was injured during both the rapid compression and decompression. In talking with company maintenance and operations officials, this was the first time they'd heard of a situation where the outflow valve was uncontrollable in the closed position. My recommendation would be for the manufacturer to come up with a procedure for this emergency. It sure would've helped if we could've had some troubleshooting ideas/steps to try so we didn't have to land fully pressurized. Callback conversation with reporter revealed the following information: the reporter states that his company changed the outflow valve and the pressure controller. This seems to have fixed the problem. The reporter has not heard of any other instance of this situation happening. The crew did not try closing any bleed valves while airborne. His company is in the process of making a procedure to fit this situation. The aircraft manufacturer has no history on this situation, and no procedure for it.

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Original NASA ASRS Text

Title: THE OUTFLOW VALVE ON AN LGT FAILED TO THE CLOSED POS. IT OPENED NORMALLY ON TOUCHDOWN.

Narrative: ON THIS PARTICULAR FLT, WE EXPERIENCED A PRESSURIZATION PROBLEM WHICH IS NEITHER ADDRESSED IN COMPANY NOR MANUFACTURER'S MANUALS. AT 10000 FT MSL, THE AUTO SYS FAILED AND OUR FE SWITCHED TO THE STANDBY SYS. CLBING THROUGH 18000 FT MSL, THE ENTIRE PRESSURIZATION SYS FAILED (AUTO, STANDBY, MANUAL AC/DC) AND THE OUTFLOW VALVE FAILED IN THE CLOSED POS WHICH CAUSED THE PRESSURIZATION SYS TO CLB TO THE 9.6 PSI RELIEF VALVE LIMIT IN A SHORT TIME SPAN. THE CAPT ELECTED NOT TO TROUBLESHOOT FURTHER AND LAND IMMEDIATELY AT DFW. ON DSCNT, THE CABIN REMAINED AT 9.6 PSI DIFFERENTIAL. ON LNDG THE SQUAT SWITCH ON THE MAIN GEAR OPENED THE OUTFLOW VALVE AND WE EXPERIENCED A RAPID DECOMPRESSION WHICH FILLED THE ACFT WITH A CLOUD OF MOISTURE FOR 5-10 SECONDS WHICH QUICKLY DISSIPATED. FORTUNATELY NOBODY WAS INJURED DURING BOTH THE RAPID COMPRESSION AND DECOMPRESSION. IN TALKING WITH COMPANY MAINT AND OPS OFFICIALS, THIS WAS THE FIRST TIME THEY'D HEARD OF A SITUATION WHERE THE OUTFLOW VALVE WAS UNCTLABLE IN THE CLOSED POS. MY RECOMMENDATION WOULD BE FOR THE MANUFACTURER TO COME UP WITH A PROC FOR THIS EMER. IT SURE WOULD'VE HELPED IF WE COULD'VE HAD SOME TROUBLESHOOTING IDEAS/STEPS TO TRY SO WE DIDN'T HAVE TO LAND FULLY PRESSURIZED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATES THAT HIS COMPANY CHANGED THE OUTFLOW VALVE AND THE PRESSURE CTLR. THIS SEEMS TO HAVE FIXED THE PROBLEM. THE RPTR HAS NOT HEARD OF ANY OTHER INSTANCE OF THIS SITUATION HAPPENING. THE CREW DID NOT TRY CLOSING ANY BLEED VALVES WHILE AIRBORNE. HIS COMPANY IS IN THE PROCESS OF MAKING A PROC TO FIT THIS SITUATION. THE ACFT MANUFACTURER HAS NO HISTORY ON THIS SITUATION, AND NO PROC FOR IT.

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.