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.