Narrative:

We were cruising at FL410, mach .79 when the left bleed trip off light illuminated. I pressed the trip reset button and the left bleed system reset momentarily. As I began to run the checklist, the left bleed trip off light reilluminated. This time it did not reset. My first officer noticed the cabin pressure rising at greater than 2000 FPM. The cabin altimeter was rising past 9000 ft. I requested a lower altitude with ZOA and was given either FL330 or FL370. Very shortly after we began our descent, the cabin altitude warning horn sounded. We accomplished the cabin altitude warning horn/decompression memory items and I requested an emergency descent to a lower altitude, I think they gave us FL290. The cabin continued to climb, it rose to 14000 ft and the masks in the cabin dropped. So I declared an emergency and we continued our descent. The flight attendants rang wanting to know what was going on. I explained the situation and asked them to ensure everybody had their masks on. I then made a PA explaining that everything was under control and that we were descending to a lower altitude. As I started to accomplish the QRH procedures, we received a frequency change and upon contacting center, we were asked our clearance altitude. I told him we were below our clearance altitude in an emergency descent because we couldn't control our cabin pressure. The center controller then stated he was declaring an emergency for us and gave us a 150 degree heading vector and a descent to 14000 ft. As we turned to 150 degree heading we received a TCASII TA and a visual on traffic crossing our nose at about our altitude. We made a slight turn to deconflict and passed approximately 3 mi to the east of the traffic. As we leveled off at 14000 ft, the cabin altitude started decreasing from a high of approximately 16000 ft. We were then given a descent to 11000 ft and after leveling, the cabin altitude came back below 10000 ft. We then proceeded to lax without any further incidents. In reviewing the incident, after the fact, I learned a few lessons and would do a couple of things differently. First, at FL410, mach .79 it takes a lot longer than I imagined to get down to 14000 ft. Because you are already pretty close to vmo/mmo, the initial descent rate is not all that impressive. Knowing this, if the QRH corrective action for bleed trip off doesn't fix the problem, you probably aren't going to prevent sounding the cabin altitude horn and dropping the masks. So, next time, I would immediately declare the emergency. I delayed in this case while I was trying to fix the problem and in the process did not give the center controller as clear a sense of the immediacy of my lower altitude requests as I would have by declaring the emergency sooner. Second, with all of the altitude requests, frequency changing and flight attendant intercom communications associated with our situation, it was difficult to execute the QRH procedures. Every time I got started, I got interrupted. I should have turned the radios over to my first officer, the PF in this case. All he had to do was fly the descent and could easily have handled the center communications once I declared the emergency. This would have freed me up to deal with the QRH, flight attendant briefing and the cabin PA. Supplemental information from acn 600062: oxygen masks on. Center was really having a hard time coordinating our descent and we weren't helping much, since oxygen masks were on, the QRH was out and communication with masks/horns/dings was difficult. He told us to stop our descent at FL290 for traffic. We were already through FL275. I called traffic in sight and the controller stated that he was declaring an emergency for us, so there was likely an ATC 'deal' or separation issue -- and he didn't know we had declared an emergency.

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Original NASA ASRS Text

Title: A B737-700 LOSES CABIN PRESSURE AT FL410 RESULTING IN AN EMER DSCNT AND OXYGEN MASK DEPLOYMENT.

Narrative: WE WERE CRUISING AT FL410, MACH .79 WHEN THE L BLEED TRIP OFF LIGHT ILLUMINATED. I PRESSED THE TRIP RESET BUTTON AND THE L BLEED SYS RESET MOMENTARILY. AS I BEGAN TO RUN THE CHKLIST, THE L BLEED TRIP OFF LIGHT REILLUMINATED. THIS TIME IT DID NOT RESET. MY FO NOTICED THE CABIN PRESSURE RISING AT GREATER THAN 2000 FPM. THE CABIN ALTIMETER WAS RISING PAST 9000 FT. I REQUESTED A LOWER ALT WITH ZOA AND WAS GIVEN EITHER FL330 OR FL370. VERY SHORTLY AFTER WE BEGAN OUR DSCNT, THE CABIN ALT WARNING HORN SOUNDED. WE ACCOMPLISHED THE CABIN ALT WARNING HORN/DECOMPRESSION MEMORY ITEMS AND I REQUESTED AN EMER DSCNT TO A LOWER ALT, I THINK THEY GAVE US FL290. THE CABIN CONTINUED TO CLB, IT ROSE TO 14000 FT AND THE MASKS IN THE CABIN DROPPED. SO I DECLARED AN EMER AND WE CONTINUED OUR DSCNT. THE FLT ATTENDANTS RANG WANTING TO KNOW WHAT WAS GOING ON. I EXPLAINED THE SIT AND ASKED THEM TO ENSURE EVERYBODY HAD THEIR MASKS ON. I THEN MADE A PA EXPLAINING THAT EVERYTHING WAS UNDER CTL AND THAT WE WERE DSNDING TO A LOWER ALT. AS I STARTED TO ACCOMPLISH THE QRH PROCS, WE RECEIVED A FREQ CHANGE AND UPON CONTACTING CTR, WE WERE ASKED OUR CLRNC ALT. I TOLD HIM WE WERE BELOW OUR CLRNC ALT IN AN EMER DSCNT BECAUSE WE COULDN'T CTL OUR CABIN PRESSURE. THE CTR CTLR THEN STATED HE WAS DECLARING AN EMER FOR US AND GAVE US A 150 DEG HDG VECTOR AND A DSCNT TO 14000 FT. AS WE TURNED TO 150 DEG HDG WE RECEIVED A TCASII TA AND A VISUAL ON TFC XING OUR NOSE AT ABOUT OUR ALT. WE MADE A SLIGHT TURN TO DECONFLICT AND PASSED APPROX 3 MI TO THE E OF THE TFC. AS WE LEVELED OFF AT 14000 FT, THE CABIN ALT STARTED DECREASING FROM A HIGH OF APPROX 16000 FT. WE WERE THEN GIVEN A DSCNT TO 11000 FT AND AFTER LEVELING, THE CABIN ALT CAME BACK BELOW 10000 FT. WE THEN PROCEEDED TO LAX WITHOUT ANY FURTHER INCIDENTS. IN REVIEWING THE INCIDENT, AFTER THE FACT, I LEARNED A FEW LESSONS AND WOULD DO A COUPLE OF THINGS DIFFERENTLY. FIRST, AT FL410, MACH .79 IT TAKES A LOT LONGER THAN I IMAGINED TO GET DOWN TO 14000 FT. BECAUSE YOU ARE ALREADY PRETTY CLOSE TO VMO/MMO, THE INITIAL DSCNT RATE IS NOT ALL THAT IMPRESSIVE. KNOWING THIS, IF THE QRH CORRECTIVE ACTION FOR BLEED TRIP OFF DOESN'T FIX THE PROB, YOU PROBABLY AREN'T GOING TO PREVENT SOUNDING THE CABIN ALT HORN AND DROPPING THE MASKS. SO, NEXT TIME, I WOULD IMMEDIATELY DECLARE THE EMER. I DELAYED IN THIS CASE WHILE I WAS TRYING TO FIX THE PROB AND IN THE PROCESS DID NOT GIVE THE CTR CTLR AS CLR A SENSE OF THE IMMEDIACY OF MY LOWER ALT REQUESTS AS I WOULD HAVE BY DECLARING THE EMER SOONER. SECOND, WITH ALL OF THE ALT REQUESTS, FREQ CHANGING AND FLT ATTENDANT INTERCOM COMS ASSOCIATED WITH OUR SIT, IT WAS DIFFICULT TO EXECUTE THE QRH PROCS. EVERY TIME I GOT STARTED, I GOT INTERRUPTED. I SHOULD HAVE TURNED THE RADIOS OVER TO MY FO, THE PF IN THIS CASE. ALL HE HAD TO DO WAS FLY THE DSCNT AND COULD EASILY HAVE HANDLED THE CTR COMS ONCE I DECLARED THE EMER. THIS WOULD HAVE FREED ME UP TO DEAL WITH THE QRH, FLT ATTENDANT BRIEFING AND THE CABIN PA. SUPPLEMENTAL INFO FROM ACN 600062: OXYGEN MASKS ON. CTR WAS REALLY HAVING A HARD TIME COORDINATING OUR DSCNT AND WE WEREN'T HELPING MUCH, SINCE OXYGEN MASKS WERE ON, THE QRH WAS OUT AND COM WITH MASKS/HORNS/DINGS WAS DIFFICULT. HE TOLD US TO STOP OUR DSCNT AT FL290 FOR TFC. WE WERE ALREADY THROUGH FL275. I CALLED TFC IN SIGHT AND THE CTLR STATED THAT HE WAS DECLARING AN EMER FOR US, SO THERE WAS LIKELY AN ATC 'DEAL' OR SEPARATION ISSUE -- AND HE DIDN'T KNOW WE HAD DECLARED AN EMER.

Data retrieved from NASA's ASRS site as of July 2007 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.