A320 flight crew experiences a cabin pressurization anomaly at FL370 and initiates a descent. With t...

Narrative:

About 30 minutes into the flight we experienced an emergency descent ECAM at FL370. We accomplished the immediate action items; donned oxygen masks and declared an emergency. We initiated a descent to 10;000 ft. As we continued with the ECAM the pressurization stabilized at a normal position. We quickly assessed that the cabin had never exceeded approximately 8;000 ft. Since the aircraft was stable we agreed that there was no need to continue down to 10;000 ft. We coordinated with ATC to level at FL250. We called the flight attendants and they said everything in the cabin was fine and the passengers hardly noticed anything. We then continued with SOP. We referenced the flight manual because the ECAM was complete and we were left with a pressurization system 2 failure. The flight manual states that if cpc 2 fails the number 1 system will pick up the load. That appeared to be what happened. After a lengthy discussion and a systems review we agreed that there must have been a system delay in the transfer of cpc control from system 2 to system 1 thereby leading to a partial loss of pressurization resulting in the ECAM. We then discussed the situation with dispatch and maintenance. After a lengthy discussion we all agreed that continuation to destination at FL250 was the best course of action. We terminated the emergency with ATC. Finally we made a PA giving a brief description of events to the passengers.

Original NASA ASRS Text

Title: A320 flight crew experiences a cabin pressurization anomaly at FL370 and initiates a descent. With the automated controller switching to CPC 1 and the cabin pressurization remaining below 10;000 FT; the crew elects to continue to destination and land uneventfully.

Narrative: About 30 minutes into the flight we experienced an emergency descent ECAM at FL370. We accomplished the immediate action items; donned oxygen masks and declared an emergency. We initiated a descent to 10;000 FT. As we continued with the ECAM the pressurization stabilized at a normal position. We quickly assessed that the cabin had never exceeded approximately 8;000 FT. Since the aircraft was stable we agreed that there was no need to continue down to 10;000 FT. We coordinated with ATC to level at FL250. We called the flight attendants and they said everything in the cabin was fine and the passengers hardly noticed anything. We then continued with SOP. We referenced the flight manual because the ECAM was complete and we were left with a pressurization system 2 failure. The Flight Manual states that if CPC 2 fails the number 1 system will pick up the load. That appeared to be what happened. After a lengthy discussion and a systems review we agreed that there must have been a system delay in the transfer of CPC control from system 2 to system 1 thereby leading to a partial loss of pressurization resulting in the ECAM. We then discussed the situation with Dispatch and Maintenance. After a lengthy discussion we all agreed that continuation to destination at FL250 was the best course of action. We terminated the emergency with ATC. Finally we made a PA giving a brief description of events to the passengers.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1083201
Time
Date	201304
Local Time Of Day	0001-0600
Place
Locale Reference	ZOA.ARTCC
State Reference	CA
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Pressurization Control System
Person 1
Function	Pilot Not Flying First Officer
Experience	Flight Crew Last 90 Days 205 Flight Crew Total 13585 Flight Crew Type 5805
Person 2
Function	Captain Pilot Flying
Experience	Flight Crew Last 90 Days 230 Flight Crew Total 21000 Flight Crew Type 1000
Events
Anomaly	Aircraft Equipment Problem Less Severe

A320 flight crew experiences a cabin pressurization anomaly at FL370 and initiates a descent. With the automated controller switching to cpc 1 and the cabin pressurization remaining below 10;000 ft; the crew elects to continue to destination and land uneventfully.