Narrative:

8/90 we departed greater pit international with the cabin out flow valve (wheel operated) locked aft and open. This was unnoticed by me when receiving the aircraft. This item is not listed on the necessary checklists we ran at the gate during a crew change. Normally I check it for free and easy movement out of memory when going through a crew and aircraft change. This time I forgot to check it. On takeoff and climb there was no noticeable discomfort in my cars and did not realize any problem until out of 10000' at which time we got a pressurization light. The first officer brought it to my attention and we operated the pressurization wheel manually. I started my level off slowly out of 10000' and was level at 12000' and it looked like the cabin was coming under control so I let the aircraft continue a slow climb to 18000'. Somewhere in the slow climb the passenger oxy masks dropped down and the cabin was at 14000'. It also looked like the cabin altitude was decreasing so I had the passenger oxy masks restowed. Sometime just after this I realized the cabin was approaching 14000' again and redeployed the oxy masks. After a few mins we were able to get down below 10000' and the cabin pressurization was operated in automatic and it operated normally. A landing was accomplished at detroit metropolitan airport with no further incident. All passengers deplaned safely and in good spirits. If I would have known that anyone had been in the cockpit working the pressurization system, I would have completed the origination checklist, thus covering this item.

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Original NASA ASRS Text

Title: ACR MLG TOOK OFF WITH CABIN OUTFLOW VALVE LOCKED OPEN PASSENGER MASKS WERE DEPLOYED BEFORE THE FLT CREW GOT THE PRESSURIZATION UNDER CTL.

Narrative: 8/90 WE DEPARTED GREATER PIT INTL WITH THE CABIN OUT FLOW VALVE (WHEEL OPERATED) LOCKED AFT AND OPEN. THIS WAS UNNOTICED BY ME WHEN RECEIVING THE ACFT. THIS ITEM IS NOT LISTED ON THE NECESSARY CHKLISTS WE RAN AT THE GATE DURING A CREW CHANGE. NORMALLY I CHK IT FOR FREE AND EASY MOVEMENT OUT OF MEMORY WHEN GOING THROUGH A CREW AND ACFT CHANGE. THIS TIME I FORGOT TO CHK IT. ON TKOF AND CLB THERE WAS NO NOTICEABLE DISCOMFORT IN MY CARS AND DID NOT REALIZE ANY PROB UNTIL OUT OF 10000' AT WHICH TIME WE GOT A PRESSURIZATION LIGHT. THE F/O BROUGHT IT TO MY ATTN AND WE OPERATED THE PRESSURIZATION WHEEL MANUALLY. I STARTED MY LEVEL OFF SLOWLY OUT OF 10000' AND WAS LEVEL AT 12000' AND IT LOOKED LIKE THE CABIN WAS COMING UNDER CTL SO I LET THE ACFT CONTINUE A SLOW CLB TO 18000'. SOMEWHERE IN THE SLOW CLB THE PAX OXY MASKS DROPPED DOWN AND THE CABIN WAS AT 14000'. IT ALSO LOOKED LIKE THE CABIN ALT WAS DECREASING SO I HAD THE PAX OXY MASKS RESTOWED. SOMETIME JUST AFTER THIS I REALIZED THE CABIN WAS APCHING 14000' AGAIN AND REDEPLOYED THE OXY MASKS. AFTER A FEW MINS WE WERE ABLE TO GET DOWN BELOW 10000' AND THE CABIN PRESSURIZATION WAS OPERATED IN AUTOMATIC AND IT OPERATED NORMALLY. A LNDG WAS ACCOMPLISHED AT DETROIT METRO ARPT WITH NO FURTHER INCIDENT. ALL PAXS DEPLANED SAFELY AND IN GOOD SPIRITS. IF I WOULD HAVE KNOWN THAT ANYONE HAD BEEN IN THE COCKPIT WORKING THE PRESSURIZATION SYS, I WOULD HAVE COMPLETED THE ORIGINATION CHKLIST, THUS COVERING THIS ITEM.

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.