A B737-500 flight crew has loss of pressurization.

Attributes
ACN	581068
Time
Date	200305
Day	Sat
Place
Locale Reference	atc facility : zoa.artcc
State Reference	CA
Altitude	msl single value : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa.artcc tower : bna.tower
Operator	common carrier : air carrier
Make Model Name	B737-500
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
Experience	flight time last 90 days : 180 flight time total : 15000 flight time type : 5000
ASRS Report	581068
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Experience	flight time total : 15000 flight time type : 4000
ASRS Report	581067
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	aircraft : equipment problem dissipated flight crew : took precautionary avoidance action flight crew : took evasive action flight crew : overcame equipment problem
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

During cruise, cabin altitude horn activated. We donned oxygen masks and completed cabin altitude horn emergency procedure checklist. We initiated an immediate descent and leveled off at 26000 ft. Cabin was controled almost immediately by going to high on both packs and going to manual closing the outflow valve. No other indications were noted. Cust service met the aircraft and dispatch was notified en route.

Original NASA ASRS Text

Title: A B737-500 FLT CREW HAS LOSS OF PRESSURIZATION.

Narrative: DURING CRUISE, CABIN ALT HORN ACTIVATED. WE DONNED OXYGEN MASKS AND COMPLETED CABIN ALT HORN EMER PROC CHKLIST. WE INITIATED AN IMMEDIATE DSCNT AND LEVELED OFF AT 26000 FT. CABIN WAS CTLED ALMOST IMMEDIATELY BY GOING TO HIGH ON BOTH PACKS AND GOING TO MANUAL CLOSING THE OUTFLOW VALVE. NO OTHER INDICATIONS WERE NOTED. CUST SVC MET THE ACFT AND DISPATCH WAS NOTIFIED ENRTE.

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.