A B737-300 captain reported the cabin altitude warning horn sounding at FL370 after one hour at crui...

Attributes
ACN	893415
Time
Date	201006
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Pressurization Control System
Person 1
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 153
Person 2
Function	First Officer
Experience	Flight Crew Last 90 Days 153
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

After an hour at FL370; we got the cabin altitude warning horn. We donned oxygen masks and established communications. The cabin was at 10;000 ft and climbing 500 FPM. We ran the QRH and were unable to stabilize the cabin with manual control. We declared an emergency; got clearance for a descent; and began an emergency descent turning direct to a nearby airport. The cabin maxed out at 12;500 ft. Around 17;000 ft; we felt a large pressure change and noted a 4;000 FPM climb in pressure. We stabilized the cabin around 5;000 ft using the manual control. We removed our masks and leveled at 10;000 ft. During the descent we talked to the flight attendants; sent an ACARS to dispatch; informed the passengers of our malfunction; and diverted to oma. We flew the ILS visual approach to 18. The crew worked well together and the whole event seemed to go very smoothly.

Original NASA ASRS Text

Title: A B737-300 Captain reported the Cabin Altitude Warning horn sounding at FL370 after one hour at cruise. An emergency was declared; a descent begun and the flight diverted to a nearby airport after the Manual Pressurization Mode would not control cabin pressure.

Narrative: After an hour at FL370; we got the Cabin Altitude Warning horn. We donned oxygen masks and established communications. The cabin was at 10;000 FT and climbing 500 FPM. We ran the QRH and were unable to stabilize the cabin with manual control. We declared an emergency; got clearance for a descent; and began an emergency descent turning direct to a nearby airport. The cabin maxed out at 12;500 FT. Around 17;000 FT; we felt a large pressure change and noted a 4;000 FPM climb in pressure. We stabilized the cabin around 5;000 FT using the manual control. We removed our masks and leveled at 10;000 FT. During the descent we talked to the Flight Attendants; sent an ACARS to Dispatch; informed the passengers of our malfunction; and diverted to OMA. We flew the ILS visual approach to 18. The crew worked well together and the whole event seemed to go very smoothly.

Data retrieved from NASA's ASRS site as of April 2012 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.

A B737-300 captain reported the cabin altitude warning horn sounding at FL370 after one hour at cruise. An emergency was declared; a descent begun and the flight diverted to a nearby airport after the manual pressurization mode would not control cabin pressure.