<< >> NASA ASRS Report 435827, April 1999

A B737-500 lost control of cabin pressurization and began a descent per the quick reference checklist procedure. During the descent, control was re-established and flight diverted to ord for the landing.

Attributes
ACN	435827
Time
Date	199904
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : elx.vortac
State Reference	MI
Altitude	msl single value : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 200 flight time total : 14000 flight time type : 280
ASRS Report	435827
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial
Experience	flight time last 90 days : 180 flight time total : 7600 flight time type : 1200
ASRS Report	435828
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other flight crewa other flight crewb
Resolutory Action	aircraft : equipment problem dissipated flight crew : landed as precaution
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Shortly after leveling off cruise altitude of FL330, cabin altitude warning horn sounded. Cabin altitude was slightly above 10000 ft and slowly climbing. Lower altitude was immediately requested and granted by ATC. Accomplished quick reference checklist items for rapid depressurization. After descending 2000-3000 ft and with packs in high flow per procedure, cabin altitude was below 10000 ft and descending. No emergency was declared. Passenger oxygen was not deployed. No injuries or clearance violations. Returned to ord for landing.

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Original NASA ASRS Text

Title: A B737-500 LOST CTL OF CABIN PRESSURIZATION AND BEGAN A DSCNT PER THE QUICK REF CHKLIST PROC. DURING THE DSCNT, CTL WAS RE-ESTABLISHED AND FLT DIVERTED TO ORD FOR THE LNDG.

Narrative: SHORTLY AFTER LEVELING OFF CRUISE ALT OF FL330, CABIN ALT WARNING HORN SOUNDED. CABIN ALT WAS SLIGHTLY ABOVE 10000 FT AND SLOWLY CLBING. LOWER ALT WAS IMMEDIATELY REQUESTED AND GRANTED BY ATC. ACCOMPLISHED QUICK REF CHKLIST ITEMS FOR RAPID DEPRESSURIZATION. AFTER DSNDING 2000-3000 FT AND WITH PACKS IN HIGH FLOW PER PROC, CABIN ALT WAS BELOW 10000 FT AND DSNDING. NO EMER WAS DECLARED. PAX OXYGEN WAS NOT DEPLOYED. NO INJURIES OR CLRNC VIOLATIONS. RETURNED TO ORD FOR 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.