AN AIRBUS A320 IN CRUISE AT FL350 DECLARED AN EMER AND MADE AN EMER DSCNT DUE TO INSTANTANEOUS LOSS OF CABIN PRESSURE.

Narrative

ELECTRONIC CENTRALIZED ACFT MONITORING (ECAM) PRESSURIZATION #2 CTL FAILURE -- NO AUTO SWITCHING TO #1. DROVE OUTFLOW VALVE FULL OPEN; CAUSED CABIN VERT SPD TO CLB APPROX 7000 FPM. CABIN ABOVE 10000 FT; DONNED OXYGEN MASKS AND STARTED EMER DSCNT. CABIN EXCEEDED 14700 FT; PAX MASKS DEPLOYED. NOTIFIED ATC OF DSCNT AND EMER. DSNDING THROUGH 34300 FT GOT TA ON TCASII; LEVELED OFF; SAW ACFT ON TCASII GO BY. NO LOSS OF SEPARATION AND CONTINUED DSCNT TO 9000 FT. ACFT STRUCTURE OK; LANDED OVERWT AT 143400 LBS (MAX 142200 LBS). ALL PAX AND FLT ATTENDANTS OK. A TURN SOONER OFF AIRWAY WOULD HAVE PROVIDED MORE VERT SEPARATION. OPPOSING ACFT AT 33000 FT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT; AN AIRBUS A320; WAS A RELATIVELY NEW AIRPLANE WITH ALL THE LATEST MODIFICATIONS AND UPDATED COMPUTERS. THE RPTR SAID TWO PREVIOUS LOG ENTRIES INDICATED THAT CABIN PRESSURE WAS LOST BUT BOTH RPTS WERE SIGNED OFF AS GND CHKS OK. THE RPTR SAID THE ACFT WAS AT FL350 WHEN THE ECAM WARNING ADVISED THE #2 PRESSURIZATION SYS FAILED AND IMMEDIATELY THE OUTFLOW VALVE WENT TO FULL OPEN DEPRESSURIZING THE CABIN. THE RPTR SAID THE SYS IS SUPPOSED TO SWITCH ELECTRONICALLY TO THE #1 SYS TO PREVENT DEPRESSURIZATION BUT IT IS SUSPECTED THAT THE SWITCH TIMING IS TOO SLOW. THE RPTR SAID AFTER THE DIVERSION AND THE REPLACEMENT OF THE #2 PRESSURE CTLR THE FLC MAINT FERRIED THE ACFT TO THE ACR OVERHAUL FACILITY AND WAS OTS FOR A PERIOD OF TIME AND THEN WAS RETURNED TO SVC AGAIN WITH THE GND CHKS OK SIGNOFF. THE RPTR STATED THE NEXT FLT WAS A SHORT 400 MI TRIP THAT WAS UNEVENTFUL BUT ON THE RETURN FLT THE CABIN AGAIN LOST PRESSURIZATION WITH AN ECAM #2 FAIL INDICATION. THE RPTR SAID A CONFERENCE CALL WAS ARRANGED WITH ALL THE CAPTS WHO FLEW THIS ACFT AND OTHERS WHO EXPERIENCED A320 CABIN PRESSURE SYS FAILURES AND THE DETAILS WERE IN ACCORDANCE WITH WHAT THE RPTR EXPERIENCED. THE RPTR STATED THAT TO THE RPTR'S KNOWLEDGE THE PROB HAS NOT BEEN SOLVED. SUPPLEMENTAL DATA RECEIVED FROM MAINT INDICATES THE #2 PRESSURE CTLR REMOVED AT THE DIVERSION STATION WAS REINSTALLED IN THE ACFT AT THE ACR OVERHAUL FACILITY IN ERROR AND THIS UNIT WAS THE CAUSE OF TWO DEPRESSURIZATION INCIDENTS.