Narrative:

It was my leg and we were at cruise flight at 40000 feet. We got an autofail light on the pressurization panel. I immediately grabbed the QRH to reference the emergency procedure. We started running the checklist. We had an autofail light with an uncontrollable cabin altitude. We then asked ATC for a lower altitude; but were not allowed to descend. The QRH directed us to go to alternate on the pressurization panel. We then selected alternate (altn). At this point the autofail light was still illuminated and the cabin altitude was uncontrollable. The QRH then says to go to manual mode and to manually open and close the valve as needed to control the cabin altitude. The captain then began controlling the cabin manually with the toggle selector. He pressed the manual switch slightly and I started to see the differential pressure climb into the caution range and moving toward the max differential limit. I then heard the captain say oxygen masks on and 100 percent. After I donned the mask I looked up and saw that we had exceeded max differential pressure. We established communication and checked that the seatbelt sign was on. The captain kept running the checklist and I notified ATC that we needed a lower altitude immediately. ATC allowed us to descend to 36000 feet initially and then 32000 feet. I initiated an emergency descent and I continued to ask for lower altitudes and after consulting with the captain I [notified ATC] for a pressurization problem. I asked for 10;000 feet and asked to divert. Meanwhile the captain worked through the autofail checklist and had moved to the rapid depressurization and emergency descent checklist. The captain was also communicating to the flight attendants; passengers and was attempting to contact dispatch. After getting things stabilized the captain and I came back together as a team to communicate what had been completed by each of us; so that we both could gain situational awareness of what had transpired. He told me that he had completed the checklist down to the deferred items and I told him that I had the airplane set up to land and was ready to brief him for the landing whenever he was caught up. We then briefed and continued uneventfully. After landing the mechanic verified that the primary and alternate pressurization controller were not working and he was suspicious that the manual mode wasn't working correctly. We did not receive the final diagnosis before leaving the aircraft. The captain and I debriefed the flight and determined the following. Communication with the masks on made it challenging; but we were able to work through it. We did a good job of dividing duties to make sure that the airplane was being flown; checklists were being completed and situational awareness remained high. I would attribute this to our CRM training program.

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Original NASA ASRS Text

Title: A Flight Crew reported loss of pressurization in the cockpit requiring an emergency descent and diversion to the nearest suitable airport.

Narrative: It was my leg and we were at cruise flight at 40000 feet. We got an autofail light on the pressurization panel. I immediately grabbed the QRH to reference the emergency procedure. We started running the checklist. We had an autofail light with an uncontrollable cabin altitude. We then asked ATC for a lower altitude; but were not allowed to descend. The QRH directed us to go to alternate on the pressurization panel. We then selected alternate (ALTN). At this point the autofail light was still illuminated and the cabin altitude was uncontrollable. The QRH then says to go to manual mode and to manually open and close the valve as needed to control the cabin altitude. The Captain then began controlling the cabin manually with the toggle selector. He pressed the manual switch slightly and I started to see the differential pressure climb into the caution range and moving toward the max differential limit. I then heard the Captain say oxygen masks on and 100 percent. After I donned the mask I looked up and saw that we had exceeded max differential pressure. We established communication and checked that the seatbelt sign was on. The Captain kept running the checklist and I notified ATC that we needed a lower altitude immediately. ATC allowed us to descend to 36000 feet initially and then 32000 feet. I initiated an emergency descent and I continued to ask for lower altitudes and after consulting with the Captain I [notified ATC] for a pressurization problem. I asked for 10;000 feet and asked to divert. Meanwhile the Captain worked through the autofail checklist and had moved to the rapid depressurization and emergency descent checklist. The Captain was also communicating to the flight attendants; passengers and was attempting to contact Dispatch. After getting things stabilized the Captain and I came back together as a team to communicate what had been completed by each of us; so that we both could gain situational awareness of what had transpired. He told me that he had completed the checklist down to the deferred items and I told him that I had the airplane set up to land and was ready to brief him for the landing whenever he was caught up. We then briefed and continued uneventfully. After landing the mechanic verified that the primary and alternate pressurization controller were not working and he was suspicious that the manual mode wasn't working correctly. We did not receive the final diagnosis before leaving the aircraft. The Captain and I debriefed the flight and determined the following. Communication with the masks on made it challenging; but we were able to work through it. We did a good job of dividing duties to make sure that the airplane was being flown; checklists were being completed and situational awareness remained high. I would attribute this to our CRM training program.

Data retrieved from NASA's ASRS site 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.