Narrative:

On climb out at approximately 600 ft we got a pack light on the left pack. I called for the after takeoff checklist and the pack light checklist and the first officer completed both [from] the qrc. The pack light did not extinguish after completing the steps in the qrc. We were unable to notify line maintenance due to radio problems.we confirmed the aircraft was pressurizing and continued our climb out. We were eventually able to contact maintenance control through dispatch and line maintenance. We confirmed with both that there were no altitude restrictions associated with single pack operations and we continued our climb to FL350; monitoring cabin pressurization as we climbed.a short time later we got the cabin altitude warning horn. We donned our oxygen masks and established communications. The pilot monitoring completed the qrc cabin altitude warning checklist and the continuation of that checklist out of the QRH. The cabin altitude was not stabilizing with the outflow valve switch closed. Simultaneously we coordinated a descent with ATC and declared an emergency and indicated our intentions to return to our departure airport. The cabin altitude got to approximately 12;000 ft before it stabilized as we descended. I notified the cabin crew of our problem and intentions to return. As we continued our descent we coordinated our return with dispatch; informed them of our problem and that we had declared an emergency with ATC. We also advised the passenger oxygen masks had not deployed because the cabin altitude had not gotten above 12;000 ft.we leveled off at 14;000 ft and the cabin altitude stabilized at approximately 8;000 ft. We removed our oxygen masks once the cabin stabilized below 10;000 ft. I briefed the flight attendants and informed the passengers of our emergency and plan to return. We confirmed with dispatch that we had plenty of fuel to return and; with no other anomalies; landed normally. We taxied into the gate where we were met by maintenance personnel.I was later informed by maintenance control that the right pack duct work had blown out causing the aircraft to lose pressurization. One of the biggest problems we had was initially contacting maintenance control because of radio frequency problems [perhaps due to joint use by operations and de-ice crews]. I suggest that while de-icing procedures are in effect that the de-icing crews use a different frequency than operations and maintenance. I also suggest that some type of back up radio be available when the station is experiencing radio difficulties.

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Original NASA ASRS Text

Title: A B737-900 returned to the departure airport when the pressurization system failed.

Narrative: On climb out at approximately 600 FT we got a PACK light on the Left Pack. I called for the After Takeoff Checklist and the PACK light checklist and the First Officer completed both [from] the QRC. The PACK light did not extinguish after completing the steps in the QRC. We were unable to notify Line Maintenance due to radio problems.We confirmed the aircraft was pressurizing and continued our climb out. We were eventually able to contact Maintenance Control through Dispatch and Line Maintenance. We confirmed with both that there were no altitude restrictions associated with single pack operations and we continued our climb to FL350; monitoring cabin pressurization as we climbed.A short time later we got the Cabin Altitude Warning Horn. We donned our oxygen masks and established communications. The Pilot Monitoring completed the QRC Cabin Altitude Warning checklist and the continuation of that checklist out of the QRH. The cabin altitude was not stabilizing with the outflow valve switch closed. Simultaneously we coordinated a descent with ATC and declared an emergency and indicated our intentions to return to our departure airport. The cabin altitude got to approximately 12;000 FT before it stabilized as we descended. I notified the cabin crew of our problem and intentions to return. As we continued our descent we coordinated our return with Dispatch; informed them of our problem and that we had declared an emergency with ATC. We also advised the passenger oxygen masks had not deployed because the cabin altitude had not gotten above 12;000 FT.We leveled off at 14;000 FT and the cabin altitude stabilized at approximately 8;000 FT. We removed our oxygen masks once the cabin stabilized below 10;000 FT. I briefed the flight attendants and informed the passengers of our emergency and plan to return. We confirmed with Dispatch that we had plenty of fuel to return and; with no other anomalies; landed normally. We taxied into the gate where we were met by Maintenance Personnel.I was later informed by Maintenance control that the Right PACK duct work had blown out causing the aircraft to lose pressurization. One of the biggest problems we had was initially contacting Maintenance Control because of radio frequency problems [perhaps due to joint use by Operations and de-ice crews]. I suggest that while de-icing procedures are in effect that the de-icing crews use a different frequency than Operations and Maintenance. I also suggest that some type of back up radio be available when the station is experiencing radio difficulties.

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.