A B737-200 in cruise at FL350 requested an emergency descent to FL280 then to 10000 ft due to loss of cabin pressure caused by the forward outflow valve.

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Attributes
ACN	419929
Time
Date	199811
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : dyr
State Reference	TN
Altitude	msl bound lower : 35000 msl bound upper : 35000
Environment
Light	Night
Aircraft 1
Controlling Facilities	artcc : zme
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : instrument pilot : flight engineer pilot : commercial
Experience	flight time last 90 days : 190 flight time total : 5500 flight time type : 1000
ASRS Report	419929
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

While climbing through FL350 to our cleared altitude of FL370 I noticed the cabin altitude approaching 10000 ft. We called for a descent and received a clearance to FL240. The cabin continued to climb above 10000 ft to approximately 11000 ft. We got clearance to descend to 10000 ft MSL. We donned oxygen masks as soon as cabin reached 10000 ft. After reaching 10000 ft the cabin stabilized at approximately 6000-7000 ft. After troubleshooting, we determined we had a faulty forward outflow valve. Eventually the forward outflow valve closed and the cabin descended on schedule.

Original NASA ASRS Text

Title: A B737-200 IN CRUISE AT FL350 REQUESTED AN EMER DSCNT TO FL280 THEN TO 10000 FT DUE TO LOSS OF CABIN PRESSURE CAUSED BY THE FORWARD OUTFLOW VALVE.

Narrative: WHILE CLBING THROUGH FL350 TO OUR CLRED ALT OF FL370 I NOTICED THE CABIN ALT APCHING 10000 FT. WE CALLED FOR A DSCNT AND RECEIVED A CLRNC TO FL240. THE CABIN CONTINUED TO CLB ABOVE 10000 FT TO APPROX 11000 FT. WE GOT CLRNC TO DSND TO 10000 FT MSL. WE DONNED OXYGEN MASKS AS SOON AS CABIN REACHED 10000 FT. AFTER REACHING 10000 FT THE CABIN STABILIZED AT APPROX 6000-7000 FT. AFTER TROUBLESHOOTING, WE DETERMINED WE HAD A FAULTY FORWARD OUTFLOW VALVE. EVENTUALLY THE FORWARD OUTFLOW VALVE CLOSED AND THE CABIN DSNDED ON SCHEDULE.

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.