Cabin altitude warning sounded on a B737-300. Flight crew declared an emergency; performed an emerge...

Attributes
ACN	780923
Time
Date	200804
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 34000
Environment
Light	Night
Aircraft 1
Controlling Facilities	artcc : zzz.artcc tower : boi.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	780923
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment other aircraft equipment : cabom a t warmomgjpd
Resolutory Action	controller : separated traffic flight crew : landed as precaution flight crew : diverted to another airport flight crew : declared emergency
Supplementary
Problem Areas	Aircraft

Narrative:

Cabin horn sounded at cruise just north of the VOR. Cabin was leaking at a rate of 500-700 FPM with a cabin altitude over 10000 ft. Both pilots donned oxygen mask and tried to stabilize cabin pressure while using the emergency QRH procedures. I squawked 7700 on the transponder to alert ATC of our emergency before starting a descent at the same time the first officer was notifying ATC of our situation. We were able to stabilize the cabin ascent by pumping more air into the cabin using high flow on both air conditioning packs. Diverted to ZZZ airport and executed a precautionary landing. Maintenance explained that this aircraft had experienced previous problems with the pressurization and they believed there was a leak that they had not been able to locate. The next day we were told the aft cargo door seal was torn and was replaced in ZZZ.

Original NASA ASRS Text

Title: CABIN ALT WARNING SOUNDED ON A B737-300. FLT CREW DECLARED AN EMER; PERFORMED AN EMER DESCENT; STABILIZED THE PRESSURIZATION; AND DIVERTED.

Narrative: CABIN HORN SOUNDED AT CRUISE JUST N OF THE VOR. CABIN WAS LEAKING AT A RATE OF 500-700 FPM WITH A CABIN ALT OVER 10000 FT. BOTH PLTS DONNED OXYGEN MASK AND TRIED TO STABILIZE CABIN PRESSURE WHILE USING THE EMER QRH PROCS. I SQUAWKED 7700 ON THE XPONDER TO ALERT ATC OF OUR EMER BEFORE STARTING A DSCNT AT THE SAME TIME THE FO WAS NOTIFYING ATC OF OUR SITUATION. WE WERE ABLE TO STABILIZE THE CABIN ASCENT BY PUMPING MORE AIR INTO THE CABIN USING HIGH FLOW ON BOTH AIR CONDITIONING PACKS. DIVERTED TO ZZZ ARPT AND EXECUTED A PRECAUTIONARY LNDG. MAINT EXPLAINED THAT THIS ACFT HAD EXPERIENCED PREVIOUS PROBS WITH THE PRESSURIZATION AND THEY BELIEVED THERE WAS A LEAK THAT THEY HAD NOT BEEN ABLE TO LOCATE. THE NEXT DAY WE WERE TOLD THE AFT CARGO DOOR SEAL WAS TORN AND WAS REPLACED IN ZZZ.

Data retrieved from NASA's ASRS site as of May 2009 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.

Cabin altitude warning sounded on a B737-300. Flight crew declared an emergency; performed an emergency descent; stabilized the pressurization; and diverted.