Narrative:

First leg of day; normal manual pressurization selected on taxi out. On climb out through 10500 ft AGL; received cabin altitude warning horn. Leveled aircraft; complied with immediate action items; and reset pressure controller after closing outflow valve to gain cabin pressure; then resumed normal operations. Rest of flight uneventful. I had just read about unpressurized takeoff errors the previous evening and had made a note that I needed to adjust my scan of checking the pressurization controller knob on the originating checklist as I usually verify cruise/landing altitudes. Unfortunately; did not notice the green manual light illuminated; nor did I verify the position of the selector knob. Will in the future have much less confidence in my first officer's and will also ensure that I doublechk this item. Fortunately; we were very heavy and our rate of climb was nil at this point. Had just received a turn and frequency change right prior to 10K; so we had not yet done the climb checklist. Supplemental information from acn 706308: it's apparent to me; as first officer; that I somehow got distraction during my originating aircraft flow to the point of leaving the controller in the manual position. Due to the number of occurrences of this type it may be worth looking at adding a pressurization confign check to the before takeoff checklist. This would give crew members a second look at the panel.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B737-700 CABIN ALT WARNING HORN SOUNDED ON CLB AT 10500 FT. THE PRESSURIZATION CTL WAS DISCOVERED IN MANUAL AND WAS RESET TO AUTO.

Narrative: FIRST LEG OF DAY; NORMAL MANUAL PRESSURIZATION SELECTED ON TAXI OUT. ON CLBOUT THROUGH 10500 FT AGL; RECEIVED CABIN ALT WARNING HORN. LEVELED ACFT; COMPLIED WITH IMMEDIATE ACTION ITEMS; AND RESET PRESSURE CONTROLLER AFTER CLOSING OUTFLOW VALVE TO GAIN CABIN PRESSURE; THEN RESUMED NORMAL OPS. REST OF FLT UNEVENTFUL. I HAD JUST READ ABOUT UNPRESSURIZED TKOF ERRORS THE PREVIOUS EVENING AND HAD MADE A NOTE THAT I NEEDED TO ADJUST MY SCAN OF CHKING THE PRESSURIZATION CONTROLLER KNOB ON THE ORIGINATING CHKLIST AS I USUALLY VERIFY CRUISE/LNDG ALTS. UNFORTUNATELY; DID NOT NOTICE THE GREEN MANUAL LIGHT ILLUMINATED; NOR DID I VERIFY THE POS OF THE SELECTOR KNOB. WILL IN THE FUTURE HAVE MUCH LESS CONFIDENCE IN MY FO'S AND WILL ALSO ENSURE THAT I DOUBLECHK THIS ITEM. FORTUNATELY; WE WERE VERY HVY AND OUR RATE OF CLB WAS NIL AT THIS POINT. HAD JUST RECEIVED A TURN AND FREQ CHANGE RIGHT PRIOR TO 10K; SO WE HAD NOT YET DONE THE CLB CHKLIST. SUPPLEMENTAL INFO FROM ACN 706308: IT'S APPARENT TO ME; AS FO; THAT I SOMEHOW GOT DISTR DURING MY ORIGINATING ACFT FLOW TO THE POINT OF LEAVING THE CONTROLLER IN THE MANUAL POS. DUE TO THE NUMBER OF OCCURRENCES OF THIS TYPE IT MAY BE WORTH LOOKING AT ADDING A PRESSURIZATION CONFIGN CHK TO THE BEFORE TKOF CHKLIST. THIS WOULD GIVE CREW MEMBERS A SECOND LOOK AT THE PANEL.

Data retrieved from NASA's ASRS site as of January 2009 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.