Narrative:

Just as we were about to read the climb checklist; we were given a climb to fl 190 and the cabin altitude warning horn sounded. We quickly donned our masks and established communications with each other as per the procedures. I commanded to stop the climb and proceeded to accomplish the checklist items per the QRH. All appeared to be in the proper positions (packs; bleed air; company and controller mode). The outflow valve was at a midpoint position and the cabin was at aircraft altitude. I moved the controller to manual and then attempted to move the outflow valve; initially in the wrong direction by mistake; and then to close position. We noted no movement either way. We were cleared to 10;000 feet and we removed our masks. I asked for a clearance back and did not declare an emergency. I felt that all we now had was an event of a non-pressurized aircraft that did not warrant trucks or priority handling. We were vectored for a thirty NM final and accomplished a normal arrival.I do not know why this happened but I do have a few afterthought suggestions. In a scenario such as this I would suggest always declaring the emergency. You would still get all the vectors and time you would need; but it may help relieve the pressures of traffic surveillance a bit. Instead of looking up the frequency for ILS; I should have just asked. If the aircraft has the capability; always keep the ILS frequency for the return on one side of one crew member navigation control box. Donning O2 masks during recurrent training should be done from the sitting position with the headset on (glasses too; if used for flight) so as to experience the reality of the item interference.

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Original NASA ASRS Text

Title: A B737 Flight Crew experienced a cabin altitude warning horn passing 10000 feet during climb. Attempts to regain control of cabin pressurization were unsuccessful. Flight returned to the departure airport.

Narrative: Just as we were about to read the Climb Checklist; we were given a climb to FL 190 and the Cabin Altitude Warning horn sounded. We quickly donned our masks and established communications with each other as per the procedures. I commanded to stop the climb and proceeded to accomplish the checklist items per the QRH. All appeared to be in the proper positions (packs; bleed air; Company and Controller mode). The outflow valve was at a midpoint position and the cabin was at aircraft altitude. I moved the controller to manual and then attempted to move the outflow valve; initially in the wrong direction by mistake; and then to close position. We noted no movement either way. We were cleared to 10;000 feet and we removed our masks. I asked for a clearance back and did not declare an emergency. I felt that all we now had was an event of a non-pressurized aircraft that did not warrant trucks or priority handling. We were vectored for a thirty NM final and accomplished a normal arrival.I do not know why this happened but I do have a few afterthought suggestions. In a scenario such as this I would suggest always declaring the emergency. You would still get all the vectors and time you would need; but it may help relieve the pressures of traffic surveillance a bit. Instead of looking up the frequency for ILS; I should have just asked. If the aircraft has the capability; always keep the ILS frequency for the return on one side of one Crew Member NAV control box. Donning O2 masks during recurrent training should be done from the sitting position with the headset on (glasses too; if used for flight) so as to experience the reality of the item interference.

Data retrieved from NASA's ASRS site as of April 2012 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.