B737 crew lost cabin pressurization and made an emergency descent in ZLA class a.

Attributes
ACN	629406
Time
Date	200409
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zla.artcc
State Reference	CA
Altitude	msl single value : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla.artcc
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
Experience	flight time last 90 days : 186 flight time total : 17000 flight time type : 7000
ASRS Report	629406
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude
Independent Detector	aircraft equipment other aircraft equipment : cabin altitude warning horn. other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance other
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

While level at FL350 en route to oak, cabin altitude horn sounded. Cabin altitude indicated 10000 ft and climbing. No other system failures or indications annunciated. We immediately donned oxygen masks which made communicating difficult. While performing checklist procedures, I requested an immediate descent and took control of aircraft from first officer. Autoplt was inadvertently disengaged and aircraft was allowed to descend prior to receiving clearance from ATC. Pressurization was restored and normal descent was requested an given by ATC.

Original NASA ASRS Text

Title: B737 CREW LOST CABIN PRESSURIZATION AND MADE AN EMER DSCNT IN ZLA CLASS A.

Narrative: WHILE LEVEL AT FL350 ENRTE TO OAK, CABIN ALT HORN SOUNDED. CABIN ALT INDICATED 10000 FT AND CLBING. NO OTHER SYS FAILURES OR INDICATIONS ANNUNCIATED. WE IMMEDIATELY DONNED OXYGEN MASKS WHICH MADE COMMUNICATING DIFFICULT. WHILE PERFORMING CHKLIST PROCS, I REQUESTED AN IMMEDIATE DSCNT AND TOOK CTL OF ACFT FROM FO. AUTOPLT WAS INADVERTENTLY DISENGAGED AND ACFT WAS ALLOWED TO DSND PRIOR TO RECEIVING CLRNC FROM ATC. PRESSURIZATION WAS RESTORED AND NORMAL DSCNT WAS REQUESTED AN GIVEN BY ATC.

Data retrieved from NASA's ASRS site as of July 2007 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.