A319
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 150; Flight Crew Total 24000; Flight Crew Type 10000
Aircraft Equipment Problem Less Severe
Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Aircraft
We were cleared by [ATC] to descend via the arrival which has some altitude restrictions and a bottom altitude of 9;000. The First Officer (FO) was Pilot Flying (PF). Descent was started from FL380. At approximately FL310 the pressurization page came up on the lower ECAM with a green cabin altitude flashing 9;300. It also showed the outflow valve full open in Amber. The FO was wearing a watch with an altimeter and he said his reading was 8;700 and climbing. I directed that masks be donned and an expedited descent to a lower altitude. I sat the passengers and told the flight attendants that we were unable to control the cabin altitude and to expect O2 Masks to deploy. The FO told ATC we were in an emergency descent and asked for clearance to 9;000 without restriction and this was granted by ATC. I was analyzing our problem and went to manual mode on the cabin pressure controller. This had no effect on the outflow valve which appeared to have failed in the full open position. The cabin was continuing to climb and eventually reached a maximum of 11;400. Cabin differential pressure was 0.3 PSI and the over pressure valve was full open and Amber as well. I cycled the pressurization controller back to auto with no change but by this time we were descending below 11;400 and the cabin also started to descend. I asked for a clearance to 7;000 which was granted by ATC. We were also given a heading and cleared for the visual approach to 16L. Descending through 10;000 both pilots removed their O2 masks and normal but unpressurized flight resumed. All checklists were performed in a timely manner and a normal landing was made.The O2 masks never deployed and I doubt the passengers were even aware of the emergency descent. Post flight the flight attendants mentioned they could feel their ears popping but outside of that there was no real indication of our pressurization problem. Once we got below 10;000 I told ATC that we were no longer an emergency and that everything was normal. On final with the gear down and flaps full the over pressure relief valve closed on its own but the outflow valve stayed full open and Amber. By cycling to manual mode and then back to auto during the rapid descent; the cabin pressure controller changed from 2 to 1 but it too seemed to have failed as there was no change in the valves. Both were open and Amber. And like I said earlier the manual controller didn't work either. After landing the outflow valve stayed open but it went to green. I wrote the issue up with maintenance and they did a post flight check in Centralized Fault Display System (CFDS) and that only showed the over pressure relief valve had opened but nothing about the open and failed pressure controllers. Clearly we were not over pressurized with a cabin differential of 0.3 PSI. We very definitely has a cabin pressure problem with climbing cabin. Once the problem was recognized; O2 masks were donned and the FO told ATC we were in an emergency descent. The whole event from about FL310 to 10;000 was probably only 5 or 6 minutes and I felt everything was done professionally and thoroughly by the whole crew.
An A319 Captain reported a loss of cabin pressure at FL310. The flight executed an emergency descent to a safe altitude and continued to the destination.