Narrative:

First officer flying. Passing 13000 ft the altitude warning horn activated. I instructed the first officer to level off and check the cabin altimeter. It read 10000 ft. I requested a leveloff and a descent to 10000 ft from ATC. I checked the pressurization panel twice and did not notice any irregularities. The second time I was checking the panel the first officer reached up to the pack switches and turned them from off to automatic. The cabin altitude started to come back down. We ran the QRH and then continued our climb. After beating ourselves over the head about checklist discipline and how many times we looked; but did not see; it came down to I missed the pack switches 3 times. Once after start; once before takeoff; and once during the 10000 ft check. Asking myself how; I came up with some contributing factors; but no excuses. I noticed the first officer did not turn the right pack switch on after the #2 engine rolled back; but did not say anything because the temperature was comfortable. I cleared ground off after engine start and immediately turned the cockpit overhead light off plunging us into darkness. The first officer asked if we could turn the light back on to finish the checklist; but I think this interrupted his flow as well as my habit pattern of turning off the light at that point. The next opportunity to catch the switches was the before takeoff checklist. We had just started running the checklist when tower asked us to pull up to #1. Again a dark cockpit; and my triggered response to respond to tower's request I looked at the panel; but did not see; and gave the appropriate response. The next opportunity to see our error still is hard to understand. I personally think the climb checklist is a great addition to our current procedures. It should be the ultimate as soon as possible/FAA/rubber jungle stopper. So how I was able to look up see the control switch in automatic; the cabin altitude set and even a quick look at the cabin altimeter without it registering the altitude was climbing and the pack switches were in the off position. I don't know. I looked but I did not see. I think the other name for that is complacency. On a somewhat positive note; I always read the safety reports when they are published and believe that they were responsible for helping me identify the altitude warning horn for what it was; which motivated my initial response to level off. It definitely stopped the rubber jungle. So embarrassingly I submit my report to those who use the safety report as a tool; and use this experience to make me a better pilot. Read the safety reports when published. Through all the mistakes we made; it was the first time I had heard the altitude horn and my first reaction was to check the gear handle. Having read other reports about the horn it helped me identify my error quicker and stopped the rubber jungle.

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Original NASA ASRS Text

Title: A B737-300 FLT CREW RECEIVED A CABIN ALT WARNING HORN ALERT CLBING OUT OF 10000 FT; AND FOUND PACK SWITCHES HAD NOT BEEN TURNED ON AFTER ENG START.

Narrative: FO FLYING. PASSING 13000 FT THE ALT WARNING HORN ACTIVATED. I INSTRUCTED THE FO TO LEVEL OFF AND CHK THE CABIN ALTIMETER. IT READ 10000 FT. I REQUESTED A LEVELOFF AND A DSCNT TO 10000 FT FROM ATC. I CHKED THE PRESSURIZATION PANEL TWICE AND DID NOT NOTICE ANY IRREGULARITIES. THE SECOND TIME I WAS CHKING THE PANEL THE FO REACHED UP TO THE PACK SWITCHES AND TURNED THEM FROM OFF TO AUTO. THE CABIN ALT STARTED TO COME BACK DOWN. WE RAN THE QRH AND THEN CONTINUED OUR CLB. AFTER BEATING OURSELVES OVER THE HEAD ABOUT CHKLIST DISCIPLINE AND HOW MANY TIMES WE LOOKED; BUT DID NOT SEE; IT CAME DOWN TO I MISSED THE PACK SWITCHES 3 TIMES. ONCE AFTER START; ONCE BEFORE TKOF; AND ONCE DURING THE 10000 FT CHK. ASKING MYSELF HOW; I CAME UP WITH SOME CONTRIBUTING FACTORS; BUT NO EXCUSES. I NOTICED THE FO DID NOT TURN THE R PACK SWITCH ON AFTER THE #2 ENG ROLLED BACK; BUT DID NOT SAY ANYTHING BECAUSE THE TEMP WAS COMFORTABLE. I CLRED GND OFF AFTER ENG START AND IMMEDIATELY TURNED THE COCKPIT OVERHEAD LIGHT OFF PLUNGING US INTO DARKNESS. THE FO ASKED IF WE COULD TURN THE LIGHT BACK ON TO FINISH THE CHKLIST; BUT I THINK THIS INTERRUPTED HIS FLOW AS WELL AS MY HABIT PATTERN OF TURNING OFF THE LIGHT AT THAT POINT. THE NEXT OPPORTUNITY TO CATCH THE SWITCHES WAS THE BEFORE TKOF CHKLIST. WE HAD JUST STARTED RUNNING THE CHKLIST WHEN TWR ASKED US TO PULL UP TO #1. AGAIN A DARK COCKPIT; AND MY TRIGGERED RESPONSE TO RESPOND TO TWR'S REQUEST I LOOKED AT THE PANEL; BUT DID NOT SEE; AND GAVE THE APPROPRIATE RESPONSE. THE NEXT OPPORTUNITY TO SEE OUR ERROR STILL IS HARD TO UNDERSTAND. I PERSONALLY THINK THE CLB CHKLIST IS A GREAT ADDITION TO OUR CURRENT PROCS. IT SHOULD BE THE ULTIMATE ASAP/FAA/RUBBER JUNGLE STOPPER. SO HOW I WAS ABLE TO LOOK UP SEE THE CTL SWITCH IN AUTO; THE CABIN ALT SET AND EVEN A QUICK LOOK AT THE CABIN ALTIMETER WITHOUT IT REGISTERING THE ALT WAS CLBING AND THE PACK SWITCHES WERE IN THE OFF POS. I DON'T KNOW. I LOOKED BUT I DID NOT SEE. I THINK THE OTHER NAME FOR THAT IS COMPLACENCY. ON A SOMEWHAT POSITIVE NOTE; I ALWAYS READ THE SAFETY RPTS WHEN THEY ARE PUBLISHED AND BELIEVE THAT THEY WERE RESPONSIBLE FOR HELPING ME IDENT THE ALT WARNING HORN FOR WHAT IT WAS; WHICH MOTIVATED MY INITIAL RESPONSE TO LEVEL OFF. IT DEFINITELY STOPPED THE RUBBER JUNGLE. SO EMBARRASSINGLY I SUBMIT MY RPT TO THOSE WHO USE THE SAFETY REPORT AS A TOOL; AND USE THIS EXPERIENCE TO MAKE ME A BETTER PLT. READ THE SAFETY RPTS WHEN PUBLISHED. THROUGH ALL THE MISTAKES WE MADE; IT WAS THE FIRST TIME I HAD HEARD THE ALT HORN AND MY FIRST REACTION WAS TO CHK THE GEAR HANDLE. HAVING READ OTHER RPTS ABOUT THE HORN IT HELPED ME IDENT MY ERROR QUICKER AND STOPPED THE RUBBER JUNGLE.

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.