B737-500 crew was required to make an emergency descent after they lost cabin pressurization.

Attributes
ACN	608440
Time
Date	200402
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : zdv.artcc
State Reference	CO
Altitude	msl single value : 35800
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv.artcc
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Flight Phase	climbout : vacating altitude cruise : level cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 1600
ASRS Report	608440
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : pressuritation auto fail light other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : diverted to another airport flight crew : declared emergency other
Consequence	other other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

After leveling off at FL330, ATC gave clearance to climb to FL350. Then ATC gave clearance to climb to FL370. Passing FL358, we noticed a pressurization problem, first in our ears, then with the automatic fail light in the pressurization controller. At this time, cabin altitude was at 9500 ft. The controller was shifted to standby. Altitude in the controller standby window was verified at 8000 ft (for FL370) and the outflow valve was verified closed. We knew we did not have pressurization control and coordinated an immediate descent to FL240, then 10000 ft. Accomplished the cabin altitude warning/rapid descent checklist. Descent was made at .77 mach, idle throttles, level change, boards out. Upon reaching 10000 ft, cabin was notified and dispatch was notified. It was decided that oma was a good choice for divert based on distance and WX. Non eventful landing.

Original NASA ASRS Text

Title: B737-500 CREW WAS REQUIRED TO MAKE AN EMER DSCNT AFTER THEY LOST CABIN PRESSURIZATION.

Narrative: AFTER LEVELING OFF AT FL330, ATC GAVE CLRNC TO CLB TO FL350. THEN ATC GAVE CLRNC TO CLB TO FL370. PASSING FL358, WE NOTICED A PRESSURIZATION PROB, FIRST IN OUR EARS, THEN WITH THE AUTO FAIL LIGHT IN THE PRESSURIZATION CTLR. AT THIS TIME, CABIN ALT WAS AT 9500 FT. THE CTLR WAS SHIFTED TO STANDBY. ALT IN THE CTLR STANDBY WINDOW WAS VERIFIED AT 8000 FT (FOR FL370) AND THE OUTFLOW VALVE WAS VERIFIED CLOSED. WE KNEW WE DID NOT HAVE PRESSURIZATION CTL AND COORDINATED AN IMMEDIATE DSCNT TO FL240, THEN 10000 FT. ACCOMPLISHED THE CABIN ALT WARNING/RAPID DSCNT CHKLIST. DSCNT WAS MADE AT .77 MACH, IDLE THROTTLES, LEVEL CHANGE, BOARDS OUT. UPON REACHING 10000 FT, CABIN WAS NOTIFIED AND DISPATCH WAS NOTIFIED. IT WAS DECIDED THAT OMA WAS A GOOD CHOICE FOR DIVERT BASED ON DISTANCE AND WX. NON EVENTFUL LNDG.

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.