B757-200 EXPERIENCED FAILURE OF BOTH PRESSURIZATION AUTO CONTROLLERS. FLT CREW DESCENDED AND WAS ABLE TO CONTROL CABIN MANUALLY; SO FLT WAS CONTINUED TO DEST.

Narrative

AT CRUISE; LEVEL FL360; THE RED CABIN ALT HORN AND WARNING LIGHT ILLUMINATED TO ALERT US TO THE FACT THAT THE CABIN WAS CLBING ABOVE 10000 FT. WE WERE ON AUTO CONTROLLER #2. WE DONNED OUR MASKS AND PERFORMED THE QRC FOR RAPID DECOMPRESSION; DOWN TO PERFORMING A RAPID DSCNT DUE TO UNCTLABLE CABIN. THE CABIN AT THE TIME WAS CLBING 300-500 FPM. WE ASKED ATC FOR A LOWER ALT; AND STARTED DOWN USING FLT LEVEL CHANGE AND A 2000 FPM RATE OF DSCNT. THE FO LOOKED FOR REF ACTION ITEMS CHKLIST; BUT THERE IS NONE. I SWITCHED TO AUTO CONTROLLER #1 IN ATTEMPT TO ARREST THE CABIN. IT INITIALLY STARTED TO DRIVE THE CABIN DOWN; BUT THEN WAS INEFFECTIVE AS WELL. I THEN SWITCHED TO MANUAL. AT THAT POINT; THE CABIN CONTROL FAIL EICAS LIGHT ILLUMINATED DUE TO PLACING THE SWITCH IN MANUAL. WE WERE ABLE TO START BRINGING THE CABIN DOWN USING MANUAL. WE LEVELED OFF AT FL240; AFTER BRINGING THE CABIN DOWN TO 5500 FT OR SO. THE FO ASSUMED FLYING AND ATC COM DUTIES WHILE I CALLED DISPATCH AND MAINT. AT THAT TIME; WE HAD THE EICAS AMBER MESSAGE AND 2 STATUS MESSAGES FOR #1 AND #1 AUTO CONTROLLER FAILURE. WE DISCUSSED THE PREVIOUS LOG HISTORY OF PRESSURIZATION FAILURE ON THE DAY PREVIOUS FOR WHICH MAINT HAD REPLACED ONE OF THE AUTO CONTROLLERS. MAINT POINTED OUT THAT THE ONLY COMMON ELEMENT BTWN THE AUTO CONTROLLERS WAS THE DRIVE MOTOR TO THE OUTFLOW VALVE. AS THE MANUAL MODE USES A SEPARATE DC MOTOR; AND IT SEEMED TO BE FUNCTIONING PROPERLY; WE ALL AGREED TO CONTINUE TO ZZZ1. MAINT OFFERED TO PUT THE WRITE-UP IN THE LOGBOOK FOR US. WE CLBED BACK TO FL340 AND CONTINUED WITHOUT FURTHER INCIDENT TO ZZZ1; AFTER WRITING UP THE FO OXYGEN MASK MIKE. WHEN WE GOT TO ZZZ1; MAINT WAS UNAWARE OF THE PROB AND MAINT CTL HAD NOT MADE THE ENTRY INTO THE LOGBOOK. WE SPOKE TO ZZZ1 ABOUT THE ISSUE; AND ALSO BRIEFED THE OUTGOING CREW. ON THE WAY TO THE HOTEL; I CALLED MAINT CTL AND ASKED WHY THE ITEM HAD NOT BEEN ENTERED. IN BOTH CASES; THE SHIFT HAD CHANGED; AND I SPOKE WITH DIFFERENT INDIVIDUALS. THE MAINT CTLR THAT I SPOKE TO SAID THAT HE WOULD MAKE THE PROPER ENTRY. I THANKED HIM AND LET HIM KNOW THAT WE WOULD BE FILING THIS RPT. A COUPLE OF QUESTIONS FOR THE FLEET -- WE DID NOT GET THE EICAS CABIN ALT CTL FAIL UNTIL WE PUT THE SWITCH TO MANUAL. THAT IS THE CHKLIST THAT DIRECTS YOU TO TRY MANUAL. I WOULD SUGGEST THAT THE FLEET PERHAPS MENTION THIS CHKLIST IN REF ACTION ITEMS FOR THE QRC. MORE ON THIS NEXT WK! THANK YOU!