A320
Flight Crew Last 90 Days 220; Flight Crew Total 17000; Flight Crew Type 10000
Confusion
Aircraft Equipment Problem Less Severe
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Aircraft
While descending to FL300 ATC issued a clearance to FL240. Nearing FL300; we noticed that the pressurization page had popped up on the systems display. The systems page showed the cabin altitude pulsating green and indicating a cabin altitude of 8;900 feet. The cabin vertical speed was showing a climb of about 500 fpm. There were no other system faults indicated. We decided to expedite our descent in case the situation deteriorated further. We asked for and received an immediate clearance to 12;000 feet initially and then 10;000 feet shortly thereafter from Center. As we descended; the cabin altitude continued to drift higher at 700-800 fpm. When the indicated cabin altitude reached 10;000 feet we put our oxygen masks on and established communications. This was followed shortly thereafter by the master warning and ECAM CAB PR EXCESS CAB ALT around FL250. We completed the ECAM and also did the Emergency Descent QRH. Since we already had our clearance to 10;000 feet and were quite busy at the time; we did not declare an emergency or squawk 7700. We still had no indications of any other systems anomalies or faults at this point. The pressurization page showed the outflow valve to be in a normal position and CPC SYS1 showed green. I checked the bleed system display page and everything indicated normal outputs on it. Nevertheless; the indicated cabin altitude continued to drift higher as we descended. Passing below FL200; I selected the pressurization control to manual and tried moving the outflow valve towards closed. The outflow valve was near the first tick mark on the displayed range of movement. As I moved the outflow valve towards the closed position; the cabin vertical speed spiked downward to a 2;000 fpm descent rate and the display turned amber. Also; the safety valve indication became amber and the safety valve opened. I then moved the outflow valve back towards its original position near the first tick mark and the safety valve closed. At this point; I selected the auto mode again which brought CPC SYS2 on line with a green indication. CPC SYS2 did not appear to react any differently than CPC SYS1 did. The indicated cabin altitude peaked at about 14;500 feet which caused the passenger oxygen masks in the cabin to automatically drop. Upon reaching 10;000 feet we were able to brief the flight attendants on our status as well as make a PA to the passengers. We were then able to continue with a normal approach and landing.
On our arrival; approximately 30 minutes from landing; after an uneventful flight; Center had cleared us to descend from FL300 to FL 240. The pressurization page appeared on the lower center screen soon after that; and the cabin altitude was flashing and green; indicating approximately 8;900 feet; and the cabin rate of climb was indicating a 500-600 fpm ROC; with no associated ECAM's; or fault light on the auto pressurization switch. We donned our O2 masks; established communications; and I began an expedited descent; after accessing that there was no apparent damage to the aircraft indicated; and asked the FO to inform center we had a pressurization problem; and to request a descent to 10;000 feet; which they approved. The cabin pressure continued this climb at a rate of 500-700 fpm. The FO switched the pressurization control to manual to arrest the climbing cabin altitude; and at one point saw the cabin overpressure safety valve symbol flash amber to indicate it opened but then quickly went away when he manually opened the outflow valve in response. This was confusing; since the cabin altitude was indicating a climb. (He then selected sys. 2; no fault lights illuminated; but went back to manual in order to evacuate the odor in the cabin produced from the hot O2 generators. We were never convinced that there was anything actually wrong with the automatic systems; but still had to respond to the indicated cabin altitude climbing uncontrollably). The cabin O2 masks deployed at approximately 14;500 feet cabin altitude with the associated ECAM for excessive cabin altitude. The FO accomplished the ECAM items; and reviewed the QRH for compliance. I called the Lead Flight Attendant; and gave her a brief explanation of what was happening. She indicated no issues in the cabin with the aircraft or passengers; besides the O2 mask deployment. At no time did anyone indicate they were experiencing any ear discomfort normally associated with such a depressurization; and the pressurization system indicated no problem other than the climbing cabin altitude. Neither of us recalls looking to see what the cabin pressure differential was indicating. Upon reaching 10;000 feet; we removed our O2 masks; and I made a PA to the cabin concerning our situation; and that the O2 masks were no longer needed; reassured them that the aircraft was safe; and that we were proceeding as planned; and our ETA. We had made the decision to not declare an emergency; and proceeded to destination for an uneventful VFR approach and landing. The actions of my FO as well as the cabin crew in response to this incident were very commendable. Everyone did an outstanding job.
A320 flight crew experiences an apparent pressurization anomaly after commencing descent and receives clearance for an expedited descent to 10;000 feet. The cabin pressure indication eventually rises to 14;500 feet where the passenger oxygen masks are automatically deployed. Attempts to control the cabin pressure manually are not successful with the safety valve opening at one point; indicating a cabin over pressure.