Pressurization problem necessitates emergency descent.

Attributes
ACN	109282
Time
Date	198904
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : atl
State Reference	GA
Altitude	msl bound lower : 12000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial pilot : instrument pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 3000 flight time type : 400
ASRS Report	109282
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 70 flight time total : 15000 flight time type : 7500
ASRS Report	109194
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

En route from mco to ord, soon after level off at FL350, cabin altitude began to climb at approximately 500 FPM. Procedures for loss of pressurization were followed. Second officer was unable to control cabin pressurization in automatic, standby or manual modes. Descent to FL310 was requested and received from ZJX. We were unable to control cabin altitude at FL310. A descent was requested and received to FL240. The cabin altitude still could not be controled. The captain advised ATC of our need for an immediate descent to a lower altitude since the cabin altitude was not climbing at 1500 FPM. The controller said he would need to coordinate. The captain used his emergency authority/authorized and told center we were continuing our descent to a lower altitude. The cabin altitude reached 10000' with warning horn sounding. WX was clear with unlimited visibility. During descent center cleared us down to 12000'. Pressurization control was regained at approximately 14000'. We requested and received clearance to divert to atl. Mechanics in atl discovered a ruptured duct and a separated water separator filter.

Original NASA ASRS Text

Title: PRESSURIZATION PROBLEM NECESSITATES EMERGENCY DESCENT.

Narrative: ENRTE FROM MCO TO ORD, SOON AFTER LEVEL OFF AT FL350, CABIN ALT BEGAN TO CLB AT APPROX 500 FPM. PROCS FOR LOSS OF PRESSURIZATION WERE FOLLOWED. S/O WAS UNABLE TO CTL CABIN PRESSURIZATION IN AUTO, STANDBY OR MANUAL MODES. DSCNT TO FL310 WAS REQUESTED AND RECEIVED FROM ZJX. WE WERE UNABLE TO CTL CABIN ALT AT FL310. A DSCNT WAS REQUESTED AND RECEIVED TO FL240. THE CABIN ALT STILL COULD NOT BE CTLED. THE CAPT ADVISED ATC OF OUR NEED FOR AN IMMEDIATE DSCNT TO A LOWER ALT SINCE THE CABIN ALT WAS NOT CLBING AT 1500 FPM. THE CTLR SAID HE WOULD NEED TO COORDINATE. THE CAPT USED HIS EMER AUTH AND TOLD CTR WE WERE CONTINUING OUR DSCNT TO A LOWER ALT. THE CABIN ALT REACHED 10000' WITH WARNING HORN SOUNDING. WX WAS CLR WITH UNLIMITED VISIBILITY. DURING DSCNT CTR CLRED US DOWN TO 12000'. PRESSURIZATION CTL WAS REGAINED AT APPROX 14000'. WE REQUESTED AND RECEIVED CLRNC TO DIVERT TO ATL. MECHS IN ATL DISCOVERED A RUPTURED DUCT AND A SEPARATED WATER SEPARATOR FILTER.

Data retrieved from NASA's ASRS site as of August 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.