Narrative:

Accomplished a packs off/bleeds off takeoff. During climb out attempted to turn on the left bleed. Left bleed off light remained on and we had left engine bleed EICAS message accomplished operations manual procedure and started APU to run left air-conditioning pack in climb. Pressurization was normal. A few mins later at about 17000 ft MSL we got a left hi- stage light and left hi-stage EICAS message. Accomplished operations manual procedure. Left duct pressure was low, but right duct pressure and system was normal. Pressurization was normal. Leveled off at FL290, checked pressurization and air- conditioning, all normal. We were flight planned at FL370. Elected to cruise at FL330 to watch pressurization. Leveled at FL330, all normal. About 3-5 mins after leveloff, cabin altitude warning horn sounded and cabin altitude warning light illuminated. Right duct pressure and air- conditioning system were normal, outflow valve was closed, cabin rate of climb was 400-500 FPM. Initiated emergency descent, declared an emergency, accomplished explosive decompression/emergency descent checklists. Leveled off at 14000 ft and diverted to slc. Cabin altitude at 14000 ft stabilized at 9500 ft but would not go lower. En route to slc noticed left engine N3 indication was reading zero on both the EICAS display and the standby engine indicator. Engine was operating normally. Landed at slc with crash fire rescue equipment/emergency equipment standing by. No injuries to passenger or crew. 1 female passenger treated for hyperventilation and transported to local hospital. No aircraft damage. Pressurization had been selected to automatic #2. At slc maintenance, ran a bite check on the pressurization system. The #2 controller displayed fault problems. Visual inspection found the controller loose in the east&east rack. It had slid forward from normal position and disconnected itself. No cockpit indications of controller malfunction or switch over were ever displayed. Believe loss of pressurization due to malfunctioning/disconnected #2 pressurization controller.

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Original NASA ASRS Text

Title: A B757 IN CRUISE DECLARED AN EMER AND DIVERTED DUE TO LOSS OF CABIN PRESSURE CAUSED BY A CABIN PRESSURE CTLR LOOSE IN THE EQUIP RACK.

Narrative: ACCOMPLISHED A PACKS OFF/BLEEDS OFF TKOF. DURING CLBOUT ATTEMPTED TO TURN ON THE L BLEED. L BLEED OFF LIGHT REMAINED ON AND WE HAD L ENG BLEED EICAS MESSAGE ACCOMPLISHED OPS MANUAL PROC AND STARTED APU TO RUN L AIR-CONDITIONING PACK IN CLB. PRESSURIZATION WAS NORMAL. A FEW MINS LATER AT ABOUT 17000 FT MSL WE GOT A L HI- STAGE LIGHT AND L HI-STAGE EICAS MESSAGE. ACCOMPLISHED OPS MANUAL PROC. L DUCT PRESSURE WAS LOW, BUT R DUCT PRESSURE AND SYS WAS NORMAL. PRESSURIZATION WAS NORMAL. LEVELED OFF AT FL290, CHKED PRESSURIZATION AND AIR- CONDITIONING, ALL NORMAL. WE WERE FLT PLANNED AT FL370. ELECTED TO CRUISE AT FL330 TO WATCH PRESSURIZATION. LEVELED AT FL330, ALL NORMAL. ABOUT 3-5 MINS AFTER LEVELOFF, CABIN ALT WARNING HORN SOUNDED AND CABIN ALT WARNING LIGHT ILLUMINATED. R DUCT PRESSURE AND AIR- CONDITIONING SYS WERE NORMAL, OUTFLOW VALVE WAS CLOSED, CABIN RATE OF CLB WAS 400-500 FPM. INITIATED EMER DSCNT, DECLARED AN EMER, ACCOMPLISHED EXPLOSIVE DECOMPRESSION/EMER DSCNT CHKLISTS. LEVELED OFF AT 14000 FT AND DIVERTED TO SLC. CABIN ALT AT 14000 FT STABILIZED AT 9500 FT BUT WOULD NOT GO LOWER. ENRTE TO SLC NOTICED L ENG N3 INDICATION WAS READING ZERO ON BOTH THE EICAS DISPLAY AND THE STANDBY ENG INDICATOR. ENG WAS OPERATING NORMALLY. LANDED AT SLC WITH CFR/EMER EQUIP STANDING BY. NO INJURIES TO PAX OR CREW. 1 FEMALE PAX TREATED FOR HYPERVENTILATION AND TRANSPORTED TO LCL HOSPITAL. NO ACFT DAMAGE. PRESSURIZATION HAD BEEN SELECTED TO AUTO #2. AT SLC MAINT, RAN A BITE CHK ON THE PRESSURIZATION SYS. THE #2 CTLR DISPLAYED FAULT PROBS. VISUAL INSPECTION FOUND THE CTLR LOOSE IN THE E&E RACK. IT HAD SLID FORWARD FROM NORMAL POS AND DISCONNECTED ITSELF. NO COCKPIT INDICATIONS OF CTLR MALFUNCTION OR SWITCH OVER WERE EVER DISPLAYED. BELIEVE LOSS OF PRESSURIZATION DUE TO MALFUNCTIONING/DISCONNECTED #2 PRESSURIZATION CTLR.

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.