A RETURN LAND BY ACR MLG MANDATED BY LOSS OF CABIN PRESSURE CTL.

Narrative

THE CABIN ALT CONTINUED TO CLB AS WE LEVELED AT FL330 AND REDUCED PWR TO CRUISE. THE AUTOMATIC CTLR HAD SWITCHED TO STANDBY SYS AND TRANSFER LOCKOUT PREVENTED US FROM TRYING THE OTHER CTLR. WE SELECTED MANUAL CTL OF THE OUTFLOW VALVE AND FULLY CLOSED IT BUT THE CABIN CONTINUED TO CLB AT 800-1000 FPM. WE REQUESTED LOWER ALT AND A TURN BACK TO OUR ORIGIN (PIT). CTR CLRED US TO DSND AND TURN AND WE BEGAN THIS WHILE THE CABIN BEGAN TO PASS THROUGH 10;000 FT. WE DONNED OXYGEN MASKS AND I ASKED FOR THE CHKLISTS AFTER WE HAD ESTABLISHED COMS. I DID NOT FEEL AN EMER EXISTED; BUT THE EMER CHKLIST WAS PROBABLY THE MOST APPROPRIATE TOOL FOR THE SITUATION. ALSO; DURING IDLE DSCNT WITH THE OUTFLOW VALVE FULLY CLOSED (MANUAL) THE CABIN ALT ABRUPTLY REVERSED AND BEGAN RAPID DSCNT; WHICH REQUIRED MANUAL OPENING OF THE OUTFLOW VALVE. WE CONTINUED TO 10;000 FT AND LEVELED OFF; TOOK OFF OUR MASKS AND BECAUSE THE LEAK IN THE CABIN APPARENTLY FIXED ITSELF; WE ELECTED TO TRY THE AUTOMATIC SYS AGAIN AND IT WORKED FINE DURING OUR FLT BACK TO PIT. THE CABIN ALT MAY HAVE EXCEEDED 13;000 FT BUT DEFINITELY NOT 14;000 FT AS THE PAX OXYGEN MASKS DID NOT DEPLOY. ROUTINE LNDG CONDUCTED IN PIT.