A321
Flight Crew Air Transport Pilot (ATP)
Distraction; Troubleshooting; Workload
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft; Procedure
I was serving as captain on a flight which was the first leg of a 3-day trip. Upon arrival at the aircraft; the FO communicated that maintenance had the log book and was clearing a write-up. The gate agent informed me that she had checked with maintenance and was told it was ok to board the passengers. A mechanic brought the logbook to the cockpit and told me that the write-ups were cleared and the aircraft was good to go. I asked what had transpired and he reported that the previous crew had written up cabin pressure controllers 1 and 2 faults. Maintenance had done a computer test as well as an over pressure valve inspection and found all items in order and signed off the logbook.We departed [and] I was the pilot not flying. About 4.5 hours into the flight at FL340 the ECAM system indicated a failure of the system 1 pressure controller followed very quickly by a system 2 failure. We followed the ECAM procedure and switched to the manual outflow valve controller.The manual system worked for 5 or 10 minutes with minimal inputs. It then became apparent that the manual valve switch was no longer controlling the outflow valve. The cabin pressure differential was slowly increasing to 8.3 with no normal method available to control it. We discussed the possibility of turning off one pack. I had the FO request a lower altitude. I sent dispatch an ACARS maintenance message describing the situation as well. As we descended; the cabin began descending slowly and the differential reduced slightly to 8 PSI. We descended to 30;000 feet and then 26;000 feet. Each time we leveled; the cabin began to descend again. We then experienced a momentary pressure fluctuation of approximately 1;000 FPM up and down.I directed the FO to request 17;000 feet (still well above minimum grid sector altitude) to reduce our exposure to the possibility of losing the cabin completely and to attempt to reduce the cabin differential. The cabin differential did reduce as we dropped in altitude. Approaching 17;000 feet; manual control of the system returned. I was able to control the cabin as we descended into [our destination] and completed our landing preparation procedures until approximately 2;500 AGL when the pressurization system page indicated that the cabin was descending below sea level approximately 500 FPM down and the outflow valve depiction on the system page turned amber indicating approximately 3/4 open. As we had previously discussed as a possibility; I informed the FO that I was turning off one of the packs. When that had minimal effect; I informed the FO once again of my intentions and then turned off the other pack. We touched down with the cabin indicating approximately 1;000 feet below sea level. This made no sense with the outflow valve open and the packs off. After landing; the cabin altitude continued to indicate 1;000 feet below sea level. After clearing the runways and performing our flows; I asked the FO to see if he could open his window. It opened without any issue and the cabin altitude continued to indicate 1;000 feet below sea level. The local altimeter setting was approximately 30.12. I then turned the packs back on and taxied to the gate with a cockpit window cracked open. After shutdown at the gate we received another ECAM indicating a VENT avionics system fault.Maintenance did not know of our discrepancy when we arrived. After I informed the mechanic of the nature of the problem there was unfortunately very little additional communication accepted from us by the mechanics concerning the details of what had happened. This was unfortunate.Throughout this incident; the First Officer did a fine job of flying the airplane while I dealt with the abnormal situation.Suspect that the outflow valve is malfunctioning. It was not inspected after a dual pressure controller fault.Whether or not the problem was caused by a malfunctioning or jammed outflow valve; it would seem to make sense that a dual pressure controller failure should mandate an outflow valve inspection. Evidently that is not part of the procedure as it stands.
An A321 departed following pressurization controller maintenance and in cruise again; both pressurization controllers faulted which required a descent to maintain a pressurized cabin.