B727-200 CREW LOST CABIN PRESSURIZATION IN ZOA CLASS A AIRSPACE.

Narrative

WHILE CLBING OUT OF SACRAMENTO; CA; BOUND FOR DENVER; CO; PASSING FL285; THE CABIN ALT WARNING HORN BEGAN TO SOUND. WE (PLTS) DONNED OUR OXYGEN MASKS AND THE CAPT LEVELED THE ACFT MOMENTARILY. WE ESTABLISHED THAT THE CABIN WAS IN FACT JUST ABOVE 10000 FT AND CLBING ERRATICALLY AT 500-1500 FPM. WHILE THE SO ATTEMPTED TO REGAIN CTL OF THE CABIN; I COORDINATED FOR AN IMMEDIATE DSCNT; WHICH WAS GIVEN DOWN TO 16000 FT MSL. THE CAPT THEN BEGAN THE EMER DSCNT. SOON THEREAFTER; THE CAPT GAVE ME CTL OF THE ACFT AND BEGAN WORKING WITH THE SO TO REGAIN CABIN PRESSURE CTL AND RUN CHKLISTS. WE COULDN'T REGAIN CABIN CTL; AND I DETERMINED FROM ATC THAT MVA IN OUR AREA WAS 16000 FT; BUT WE WERE JUST 35 MI FROM RENO. THE CAPT DIRECTED TO HEAD TOWARD RENO. I COORDINATED THIS AND SOON WAS GIVEN A DSCNT TO 9000 FT. BELOW 10000 FT WE REMOVED OUR MASKS; FINISHED CHKLISTS; COORDINATED WITH OUR FLT ATTENDANTS AND LANDED UNEVENTFULLY AT RENO. THE MASKS IN THE BACK OF THE ACFT DID DEPLOY; THOUGH OUR GAUGES RPTED A MAX CABIN ALT OF 13000 FT (1500 FT LOWER THAN THE AUTOMATIC DEPLOYMENT ALT). CONSIDERATIONS: 1) COCKPIT COMS WITH OXYGEN MASKS ON IN THE B727 IS EXTREMELY CUMBERSOME. WHILE ONE PLT IS SET UP TO XMIT TO ATC; HE CANNOT HEAR THE REST OF THE CREW. 2) A WARNING OF A CABIN CLBING ABOVE SAY 8000 FT (IT SHOULD NEVER GET THAT HIGH) WOULD AFFORD THE CREW TIME TO ESTABLISH A GAME PLAN BEFORE THE NEED TO DON OXYGEN MASKS WAS WARRANTED. AS FAR AS I KNOW; WE DID NOT DEVIATE WITHOUT ATC APPROVAL. HOWEVER; WE DID EXERCISE THE CAPT'S EMER AUTH. WE NOTIFIED DISPATCH OF OUR INTENTIONS ENRTE TO RNO. I FELT THE CREW PERFORMED VERY WELL; EVEN WITH THE SIT MAKING COM VERY DIFFICULT. I ALSO FELT CTR'S PERFORMANCE WAS EXCELLENT. THEY GAVE US AN IMMEDIATE CLRNC TO LOWER ALT; THEN GOT US MOVING TOWARD RENO (ENABLING US TO GET BELOW 10000 FT) ALMOST IMMEDIATELY.