B737-700 first officer reported the primary pressurization auto controller failed; but the crew rega...

Narrative:

We were at FL390 and given a clearance to cross 50 miles west of zzzzz intersection on the STAR. At TOD; the autothrottles retarded as expected; and the aircraft started down to make the restriction on V/path. About one or two seconds into the descent; I felt a pressure bump. I looked up at the rate indicator and saw it was showing a rapid climb in cabin altitude. Of course you could feel it as well. I pointed toward the indicator; and at about the same time; we got the cabin altitude warning. We quickly donned our masks; and completed memory items. The captain (pm) quickly told ATC we were going to need a descent to 10;000 ft. He then went to work on the checklist; while I expedited our descent. In the course of following the procedure; we regained control of the pressurization. The primary auto-controller had failed; but not auto switched to the altitude mode. We were able to control pressurization using the altitude-controller once it was selected. The captain checked on the flight attendants; and made a PA to the passengers. The masks in the back had not deployed. We continued our descent and landed uneventfully. The aircraft was taken out of service; and as I recall; maintenance said the auto-controller showed various fault codes.we both thought the training we had received this year in annual training greatly aided in our ability to quickly and correctly handle this situation. Good job training department!

Original NASA ASRS Text

Title: B737-700 First Officer reported the primary pressurization auto controller failed; but the crew regained control by selecting the alternate controller.

Narrative: We were at FL390 and given a clearance to cross 50 miles west of ZZZZZ intersection on the STAR. At TOD; the autothrottles retarded as expected; and the aircraft started down to make the restriction on V/PATH. About one or two seconds into the descent; I felt a pressure bump. I looked up at the rate indicator and saw it was showing a rapid climb in cabin altitude. Of course you could feel it as well. I pointed toward the indicator; and at about the same time; we got the Cabin Altitude Warning. We quickly donned our masks; and completed memory items. The Captain (PM) quickly told ATC we were going to need a descent to 10;000 ft. He then went to work on the checklist; while I expedited our descent. In the course of following the procedure; we regained control of the pressurization. The primary auto-controller had failed; but not auto switched to the ALT mode. We were able to control pressurization using the ALT-controller once it was selected. The Captain checked on the Flight Attendants; and made a PA to the passengers. The masks in the back had not deployed. We continued our descent and landed uneventfully. The aircraft was taken out of service; and as I recall; Maintenance said the auto-controller showed various fault codes.We both thought the training we had received this year in annual training greatly aided in our ability to quickly and correctly handle this situation. Good job Training Department!

Data retrieved from NASA's ASRS site 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	1401108
Time
Date	201611
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	Pressurization Control System
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 275 Flight Crew Type 9000
Events
Anomaly	Aircraft Equipment Problem Less Severe

B737-700 first officer reported the primary pressurization auto controller failed; but the crew regained control by selecting the alternate controller.