A RETURN LAND IN A B727 MANDATED BY LOSS OF CABIN PRESSURE.

Narrative

CLBING OUT OF CVG AT APPROX 5000 FT A VERY LOUD PACK RUMBLE BEGAN ACTUALLY SHAKING THE ACFT. THE PACKS WERE ISOLATED TO DETERMINE WHICH ONE WAS MALFUNCTIONING. THE R PACK WAS TURNED OFF FIRST; THE RUMBLE CONTINUED AND THE CABIN ALT BEGAN TO INCREASE RAPIDLY. THE R PACK WAS REINSTATED AND THE L PACK WAS SECURED. THE RUMBLE STOPPED AND THE PRESSURIZATION RETURNED TO NORMAL; ALTHOUGH THE CABIN ALT WAS NOW BTWN 2500-3000 FT. CLBOUT WAS CONTINUED AND LEVELOFF AT FL230 WAS NORMAL. A PA WAS MADE TO ADVISE THE PAX THAT WE HAD AN AIR-CONDITIONING PROB; AND THAT WAS WHAT CAUSED THE NOISE AND VIBRATION. A RADIO CALL WAS THEN MADE TO OPS; MAINT AND FLT CTL TO GIVE THEM A HEADS UP PRIOR TO OUR ARR IN CLE. WHILE SO WAS TALKING WITH MAINT; THE CABIN ALT STARTED TO RISE SLOWLY (800-1000 FPM). WE REQUESTED A LOWER ALT FROM CTR AND WERE GIVEN A DSCNT TO FL210. WE ADVISED CTR WE HAD A PRESSURIZATION PROB BUT DID NOT NEED TO DECLARE AN EMER. WE WERE FIRST TOLD THERE WAS NO TFC BELOW US BUT WERE THEN GIVEN A STEP DOWN TO FL200 AND WE SAW AN ACFT IN FRONT OF AND BELOW US ON TCASII. THE CABIN THEN BEGAN AN OFF SCALE CLB ON THE CABIN ALT; WE DECLARED AN EMER; CTR VECTORED; THE TFC GOT OUT OF THE WAY; AND THE LOSS OF PRESSURIZATION AND EMER DSCNT CHKLISTS WERE PERFORMED. CTR CLRED US DOWN TO 10000 FT; BUT BEFORE WE COULD GET DOWN; THE CABIN ALT WARNING HORN SOUNDED; AND SHORTLY THEREAFTER; THE PAX OXYGEN MASKS AUTOMATICALLY DEPLOYED. THIS OCCURRED JUST N OF THE APPLETON VOR; AND SINCE WE NO LONGER HAVE MAINT IN CLE; THE CAPT DECIDED TO RETURN TO CVG. LEVEL OFF AT 10000 FT WAS NORMAL AND WE TERMINATED THE EMER. WE STILL COULD NOT REGAIN CTL OF THE PRESSURIZATION. THE CABIN ALT AND RATE OF DSCNT FOLLOWED THAT OF THE ACFT; WE DID A SLOW 700-800 FPM DSCNT INTO CVG REQUESTING A LONG DOWNWIND LEG TO MINIMIZE PAX DISCOMFORT.