Narrative:

Loss of pressurization at FL370. No warning other than master caution lights and 'overhead' on annunciator panel, as I scanned to aft overhead no other lights on. Aft overhead the 'passenger oxygen on' light illuminated indicating passenger oxygen masks had dropped. Immediately checked cabin altitude, 15000 ft and cabin rate of climb 1200 ft to 1500 FPM. Captain commanded 'descend now!!' and I disengaged autoplt, autothrottle and pulled speed brake while beginning a smooth descent and turn left. As I began to maneuver I grabbed my oxygen mask and put it on with one hand. The captain was simultaneously declaring an emergency to ZJX, squawking '7700,' and grab the pressurization mode selector to manual direct current and closed the outflow valve, which appeared fully closed. While in the descent I followed the captain's commands to avoid traffic and backed him up on the 'emergency descent checklist' items. (Traffic conflict will be discussed after emergency descent). Cabin altitude began descending when passing through 32000 ft and around 25000 to 23000 ft we regained control of cabin. I slowed descent (aircraft) around 18000 ft and cabin was below 10000 ft still descending at 2500-3000 FPM. Captain slowed and stopped cabin at 6000 ft. We then went back to FL180 for WX and diverted to clt for nearest maintenance and passenger convenience. No further problems other than a slow descent and operated pressurization in manual. Captain spoke with our maintenance control and was informed aircraft had recent history of pressurization problems with many parts replaced. Nothing noted this in our check of previous write-ups in logbook. 1ST observation -- possibly some way to advise crews of previous problems, that are not a MEL or cdl item. 2ND observation -- no matter how much training (past several aircraft B757/767, just back on B737- 300 within yr) for emergency dscnts in simulator done with autoflt system on and doing descent (all were done this way), I still did it manually so as to control maneuver (flight attendants didn't realize we were in an emergency descent, descending 6000-8000 FPM). 3RD observation -- due to FARS, use of headset are almost continuous, even at cruise due to east coast and cockpit noise levels, so switch on 'baker box' is always in 'boom' microphone and needs to be selected in to 'oxygen mask' along with overhead speaker turned on and volume adjusted all the while attempting to communicate with other crew and ATC. Almost always headset is knocked off, this case was no exception. So communication is extremely difficult, a lot of our communication was done by hand signals with nodding and 'thumbs up' so not to interfere with ATC communications because of traffic conflicts and requests. 4TH observation -- the only masks in cabin not to drop was the forward flight attendants' over their jump seat. This caused some confusion because 1 flight attendant was in lavatory (not sure which) and when it dropped she thought she had triggered it. When she came out she told other flight attendants she was going to cockpit to tell us, at which time she attempted to speak with the captain who was in the middle of advising ATC which way we were going to avoid conflicts with traffic and doing checklists. He told her to return to cabin and put on mask and situation down and to advise other flight attendants and passenger to do same. Only flight attendant in aft galley had sat down and put on mask when they dropped. No passenger put on mask until advised by flight attendant according to flight attendants. This was learned during subsequent conversations during remainder of trip. Flight attendant from lavatory that came into cockpit to advise (25 plus yrs experience) felt bad and wished she had handled differently by just sitting and taking oxygen mask and putting on. The 2 flight attendants on forward jump seat where masks did not drop, just seemed a little upset by no communication/direction from flight deck. When explained to them that we were quite occupied and what had transpired in the cockpit, all but one seemed to understand and accept. Flight attendant with 15 yr anniversary on that day seemed to still be upset, but was also obsessing about B737's rudder problems, and all other dangers in modern aviation. Other 2 flight attendants seemed ok with it (8 and 10 yrs experience). 5TH observation -- complex mechanical system due breakdown (but incredibly rare, all things considered), along with their warning system (no 10000 ft cabin horn, or controller reverting to stand- by system which would have given master caution and annunciator). Still 'passenger oxygen on' annunciator with 'master caution' got our attention before hypoxia set in. After the captain commanded the descent he picked up his microphone and declared an emergency with our intentions and problem while he then put '7700' in transponder. Initially it seemed the ZJX controller was a bit disoriented and didn't understand we were an emergency because he kept saying he couldn't give us lower than FL310 due to traffic (we had the FL290 traffic on TCASII and a few others that were not a problem). The captain then told him to turn our traffic east and we would continue our turn to west and that we had the FL290 traffic on TCASII. He reiterated this a few times. During a lull in communication traffic a deep voice came on and said 'give him what he wants he's got a problem.' after which the ZJX controller must have realized we were an emergency and cleared us to do what we needed and began vectoring the FL290 traffic (by which time we were through FL290). The controller's problem might have been that the initial call was blocked and subsequent calls blocked, he didn't realize what was going on until he saw our descent and turn along with '7700.' after this he was most accommodating. Again, a problem of possible blocked communications with subsequent hearback errors. Finally, the more I'm around TCASII the better I like it. It allowed us to do what we needed to do without that bad feeling of 'hope no one is down there in our way' in the back of your mind. We only get a 'TA' for a short time (estimate 3-4 mins here). Then a 'clear of traffic' when passing through approximately FL260.

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Original NASA ASRS Text

Title: EMER DSCNT DUE TO LOSS OF PRESSURIZATION. FLC REGAINED PRESSURIZATION CTL AND DIVERTED TO CLOSEST ARPT. SEVERAL DIFFICULTIES OCCURRED IN EMER.

Narrative: LOSS OF PRESSURIZATION AT FL370. NO WARNING OTHER THAN MASTER CAUTION LIGHTS AND 'OVERHEAD' ON ANNUNCIATOR PANEL, AS I SCANNED TO AFT OVERHEAD NO OTHER LIGHTS ON. AFT OVERHEAD THE 'PAX OXYGEN ON' LIGHT ILLUMINATED INDICATING PAX OXYGEN MASKS HAD DROPPED. IMMEDIATELY CHKED CABIN ALT, 15000 FT AND CABIN RATE OF CLB 1200 FT TO 1500 FPM. CAPT COMMANDED 'DSND NOW!!' AND I DISENGAGED AUTOPLT, AUTOTHROTTLE AND PULLED SPD BRAKE WHILE BEGINNING A SMOOTH DSCNT AND TURN L. AS I BEGAN TO MANEUVER I GRABBED MY OXYGEN MASK AND PUT IT ON WITH ONE HAND. THE CAPT WAS SIMULTANEOUSLY DECLARING AN EMER TO ZJX, SQUAWKING '7700,' AND GRAB THE PRESSURIZATION MODE SELECTOR TO MANUAL DIRECT CURRENT AND CLOSED THE OUTFLOW VALVE, WHICH APPEARED FULLY CLOSED. WHILE IN THE DSCNT I FOLLOWED THE CAPT'S COMMANDS TO AVOID TFC AND BACKED HIM UP ON THE 'EMER DSCNT CHKLIST' ITEMS. (TFC CONFLICT WILL BE DISCUSSED AFTER EMER DSCNT). CABIN ALT BEGAN DSNDING WHEN PASSING THROUGH 32000 FT AND AROUND 25000 TO 23000 FT WE REGAINED CTL OF CABIN. I SLOWED DSCNT (ACFT) AROUND 18000 FT AND CABIN WAS BELOW 10000 FT STILL DSNDING AT 2500-3000 FPM. CAPT SLOWED AND STOPPED CABIN AT 6000 FT. WE THEN WENT BACK TO FL180 FOR WX AND DIVERTED TO CLT FOR NEAREST MAINT AND PAX CONVENIENCE. NO FURTHER PROBS OTHER THAN A SLOW DSCNT AND OPERATED PRESSURIZATION IN MANUAL. CAPT SPOKE WITH OUR MAINT CTL AND WAS INFORMED ACFT HAD RECENT HISTORY OF PRESSURIZATION PROBS WITH MANY PARTS REPLACED. NOTHING NOTED THIS IN OUR CHK OF PREVIOUS WRITE-UPS IN LOGBOOK. 1ST OBSERVATION -- POSSIBLY SOME WAY TO ADVISE CREWS OF PREVIOUS PROBS, THAT ARE NOT A MEL OR CDL ITEM. 2ND OBSERVATION -- NO MATTER HOW MUCH TRAINING (PAST SEVERAL ACFT B757/767, JUST BACK ON B737- 300 WITHIN YR) FOR EMER DSCNTS IN SIMULATOR DONE WITH AUTOFLT SYS ON AND DOING DSCNT (ALL WERE DONE THIS WAY), I STILL DID IT MANUALLY SO AS TO CTL MANEUVER (FLT ATTENDANTS DIDN'T REALIZE WE WERE IN AN EMER DSCNT, DSNDING 6000-8000 FPM). 3RD OBSERVATION -- DUE TO FARS, USE OF HEADSET ARE ALMOST CONTINUOUS, EVEN AT CRUISE DUE TO EAST COAST AND COCKPIT NOISE LEVELS, SO SWITCH ON 'BAKER BOX' IS ALWAYS IN 'BOOM' MIKE AND NEEDS TO BE SELECTED IN TO 'OXYGEN MASK' ALONG WITH OVERHEAD SPEAKER TURNED ON AND VOLUME ADJUSTED ALL THE WHILE ATTEMPTING TO COMMUNICATE WITH OTHER CREW AND ATC. ALMOST ALWAYS HEADSET IS KNOCKED OFF, THIS CASE WAS NO EXCEPTION. SO COM IS EXTREMELY DIFFICULT, A LOT OF OUR COM WAS DONE BY HAND SIGNALS WITH NODDING AND 'THUMBS UP' SO NOT TO INTERFERE WITH ATC COMS BECAUSE OF TFC CONFLICTS AND REQUESTS. 4TH OBSERVATION -- THE ONLY MASKS IN CABIN NOT TO DROP WAS THE FORWARD FLT ATTENDANTS' OVER THEIR JUMP SEAT. THIS CAUSED SOME CONFUSION BECAUSE 1 FLT ATTENDANT WAS IN LAVATORY (NOT SURE WHICH) AND WHEN IT DROPPED SHE THOUGHT SHE HAD TRIGGERED IT. WHEN SHE CAME OUT SHE TOLD OTHER FLT ATTENDANTS SHE WAS GOING TO COCKPIT TO TELL US, AT WHICH TIME SHE ATTEMPTED TO SPEAK WITH THE CAPT WHO WAS IN THE MIDDLE OF ADVISING ATC WHICH WAY WE WERE GOING TO AVOID CONFLICTS WITH TFC AND DOING CHKLISTS. HE TOLD HER TO RETURN TO CABIN AND PUT ON MASK AND SIT DOWN AND TO ADVISE OTHER FLT ATTENDANTS AND PAX TO DO SAME. ONLY FLT ATTENDANT IN AFT GALLEY HAD SAT DOWN AND PUT ON MASK WHEN THEY DROPPED. NO PAX PUT ON MASK UNTIL ADVISED BY FLT ATTENDANT ACCORDING TO FLT ATTENDANTS. THIS WAS LEARNED DURING SUBSEQUENT CONVERSATIONS DURING REMAINDER OF TRIP. FLT ATTENDANT FROM LAVATORY THAT CAME INTO COCKPIT TO ADVISE (25 PLUS YRS EXPERIENCE) FELT BAD AND WISHED SHE HAD HANDLED DIFFERENTLY BY JUST SITTING AND TAKING OXYGEN MASK AND PUTTING ON. THE 2 FLT ATTENDANTS ON FORWARD JUMP SEAT WHERE MASKS DID NOT DROP, JUST SEEMED A LITTLE UPSET BY NO COM/DIRECTION FROM FLT DECK. WHEN EXPLAINED TO THEM THAT WE WERE QUITE OCCUPIED AND WHAT HAD TRANSPIRED IN THE COCKPIT, ALL BUT ONE SEEMED TO UNDERSTAND AND ACCEPT. FLT ATTENDANT WITH 15 YR ANNIVERSARY ON THAT DAY SEEMED TO STILL BE UPSET, BUT WAS ALSO OBSESSING ABOUT B737'S RUDDER PROBS, AND ALL OTHER DANGERS IN MODERN AVIATION. OTHER 2 FLT ATTENDANTS SEEMED OK WITH IT (8 AND 10 YRS EXPERIENCE). 5TH OBSERVATION -- COMPLEX MECHANICAL SYS DUE BREAKDOWN (BUT INCREDIBLY RARE, ALL THINGS CONSIDERED), ALONG WITH THEIR WARNING SYS (NO 10000 FT CABIN HORN, OR CTLR REVERTING TO STAND- BY SYS WHICH WOULD HAVE GIVEN MASTER CAUTION AND ANNUNCIATOR). STILL 'PAX OXYGEN ON' ANNUNCIATOR WITH 'MASTER CAUTION' GOT OUR ATTN BEFORE HYPOXIA SET IN. AFTER THE CAPT COMMANDED THE DSCNT HE PICKED UP HIS MIKE AND DECLARED AN EMER WITH OUR INTENTIONS AND PROB WHILE HE THEN PUT '7700' IN XPONDER. INITIALLY IT SEEMED THE ZJX CTLR WAS A BIT DISORIENTED AND DIDN'T UNDERSTAND WE WERE AN EMER BECAUSE HE KEPT SAYING HE COULDN'T GIVE US LOWER THAN FL310 DUE TO TFC (WE HAD THE FL290 TFC ON TCASII AND A FEW OTHERS THAT WERE NOT A PROB). THE CAPT THEN TOLD HIM TO TURN OUR TFC E AND WE WOULD CONTINUE OUR TURN TO W AND THAT WE HAD THE FL290 TFC ON TCASII. HE REITERATED THIS A FEW TIMES. DURING A LULL IN COM TFC A DEEP VOICE CAME ON AND SAID 'GIVE HIM WHAT HE WANTS HE'S GOT A PROB.' AFTER WHICH THE ZJX CTLR MUST HAVE REALIZED WE WERE AN EMER AND CLRED US TO DO WHAT WE NEEDED AND BEGAN VECTORING THE FL290 TFC (BY WHICH TIME WE WERE THROUGH FL290). THE CTLR'S PROB MIGHT HAVE BEEN THAT THE INITIAL CALL WAS BLOCKED AND SUBSEQUENT CALLS BLOCKED, HE DIDN'T REALIZE WHAT WAS GOING ON UNTIL HE SAW OUR DSCNT AND TURN ALONG WITH '7700.' AFTER THIS HE WAS MOST ACCOMMODATING. AGAIN, A PROB OF POSSIBLE BLOCKED COMS WITH SUBSEQUENT HEARBACK ERRORS. FINALLY, THE MORE I'M AROUND TCASII THE BETTER I LIKE IT. IT ALLOWED US TO DO WHAT WE NEEDED TO DO WITHOUT THAT BAD FEELING OF 'HOPE NO ONE IS DOWN THERE IN OUR WAY' IN THE BACK OF YOUR MIND. WE ONLY GET A 'TA' FOR A SHORT TIME (ESTIMATE 3-4 MINS HERE). THEN A 'CLR OF TFC' WHEN PASSING THROUGH APPROX FL260.

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.