Narrative:

Upon takeoff from boi, the first officer and I noticed the cabin altitude climbing at approximately 2000 FPM followed by a failure of the automatic mode for pressurization. The checklist led us to manually closing the outflow valve and I instructed the first officer (PF) to level off at 10000 ft as we were still unable to control cabin pressure. 20 mi from boi we elected to return to boi with the concurrence of dispatch. The release was amended to reflect our new destination of boi. Landing uneventful. Maximum cabin altitude reached was 10000 ft, no passenger complained of discomfort after. Upon contact with cpr maintenance and dispatch on ground, it was concluded that the aft service door had not been properly sealed for takeoff. The 'B' flight attendant described an unusually high noise level on taxi out and climb out. Upon visual inspection I could see a space of approximately 3/4 along the leading edge of the door. Cycling the door several times myself I was able to duplicate the problem. The forward roller cam mechanism for the door locking mechanism slipped off the outside of its intended track on the tongue and groove bracket located on the door frame. In this confign the lever is also positioned normally in its horizontal locked position. The gap can be seen upon inspection and is most noticeable by the unusually high noise level (from APU) in the aft galley. Improper positioning of the rolling door cam can be evidenced by the grease track it leaves on the outside of the forward locking brackets on the door frame. Contract maintenance signed off the logbook and the remainder of the days flying was uneventful.

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Original NASA ASRS Text

Title: A B737-300 AFTER TKOF WAS UNABLE TO PRESSURIZE THE CABIN WITH THE OUTFLOW VALVE FULLY CLOSED. FOUND AFT SVC DOOR OUT OF RIG AND LEAKING.

Narrative: UPON TKOF FROM BOI, THE FO AND I NOTICED THE CABIN ALT CLBING AT APPROX 2000 FPM FOLLOWED BY A FAILURE OF THE AUTO MODE FOR PRESSURIZATION. THE CHKLIST LED US TO MANUALLY CLOSING THE OUTFLOW VALVE AND I INSTRUCTED THE FO (PF) TO LEVEL OFF AT 10000 FT AS WE WERE STILL UNABLE TO CTL CABIN PRESSURE. 20 MI FROM BOI WE ELECTED TO RETURN TO BOI WITH THE CONCURRENCE OF DISPATCH. THE RELEASE WAS AMENDED TO REFLECT OUR NEW DEST OF BOI. LNDG UNEVENTFUL. MAX CABIN ALT REACHED WAS 10000 FT, NO PAX COMPLAINED OF DISCOMFORT AFTER. UPON CONTACT WITH CPR MAINT AND DISPATCH ON GND, IT WAS CONCLUDED THAT THE AFT SVC DOOR HAD NOT BEEN PROPERLY SEALED FOR TKOF. THE 'B' FLT ATTENDANT DESCRIBED AN UNUSUALLY HIGH NOISE LEVEL ON TAXI OUT AND CLBOUT. UPON VISUAL INSPECTION I COULD SEE A SPACE OF APPROX 3/4 ALONG THE LEADING EDGE OF THE DOOR. CYCLING THE DOOR SEVERAL TIMES MYSELF I WAS ABLE TO DUPLICATE THE PROB. THE FORWARD ROLLER CAM MECHANISM FOR THE DOOR LOCKING MECHANISM SLIPPED OFF THE OUTSIDE OF ITS INTENDED TRACK ON THE TONGUE AND GROOVE BRACKET LOCATED ON THE DOOR FRAME. IN THIS CONFIGN THE LEVER IS ALSO POSITIONED NORMALLY IN ITS HORIZ LOCKED POS. THE GAP CAN BE SEEN UPON INSPECTION AND IS MOST NOTICEABLE BY THE UNUSUALLY HIGH NOISE LEVEL (FROM APU) IN THE AFT GALLEY. IMPROPER POSITIONING OF THE ROLLING DOOR CAM CAN BE EVIDENCED BY THE GREASE TRACK IT LEAVES ON THE OUTSIDE OF THE FORWARD LOCKING BRACKETS ON THE DOOR FRAME. CONTRACT MAINT SIGNED OFF THE LOGBOOK AND THE REMAINDER OF THE DAYS FLYING WAS UNEVENTFUL.

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.