Large transport had pressurization problem, declare emergency and made immediate descent.

Attributes
ACN	258109
Time
Date	199311
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 10000 msl bound upper : 28000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : commercial pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 210 flight time total : 3000 flight time type : 2000
ASRS Report	258109
Person 2
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : commercial pilot : instrument pilot : flight engineer
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

I was flying (copilot), climbing through FL270. The so alerted us that the cabin was climbing 1000-1500 FPM and was approaching 10000 ft cabin altitude. She had the outflow valve completely closed. The captain alerted center that we needed a rapid descent to 10000 ft and we were squawking 7700. Center told us that there were no conflicts below and to descend to 10000 ft. I initiated a power-off, full speed brake, barberpole descent to 10000 ft. We alerted the cabin to what was happening. We requested a vector back to ord. (We were on our way to oma from ord.) we were vectored back to ord and utilized a slow descent as it was evident that the cabin was following our actual airplane altitude. We landed at ord without incident, boarded another aircraft, and completed the flight to oma.

Original NASA ASRS Text

Title: LGT HAD PRESSURIZATION PROB, DECLARE EMER AND MADE IMMEDIATE DSCNT.

Narrative: I WAS FLYING (COPLT), CLBING THROUGH FL270. THE SO ALERTED US THAT THE CABIN WAS CLBING 1000-1500 FPM AND WAS APCHING 10000 FT CABIN ALT. SHE HAD THE OUTFLOW VALVE COMPLETELY CLOSED. THE CAPT ALERTED CTR THAT WE NEEDED A RAPID DSCNT TO 10000 FT AND WE WERE SQUAWKING 7700. CTR TOLD US THAT THERE WERE NO CONFLICTS BELOW AND TO DSND TO 10000 FT. I INITIATED A PWR-OFF, FULL SPD BRAKE, BARBERPOLE DSCNT TO 10000 FT. WE ALERTED THE CABIN TO WHAT WAS HAPPENING. WE REQUESTED A VECTOR BACK TO ORD. (WE WERE ON OUR WAY TO OMA FROM ORD.) WE WERE VECTORED BACK TO ORD AND UTILIZED A SLOW DSCNT AS IT WAS EVIDENT THAT THE CABIN WAS FOLLOWING OUR ACTUAL AIRPLANE ALT. WE LANDED AT ORD WITHOUT INCIDENT, BOARDED ANOTHER ACFT, AND COMPLETED THE FLT TO OMA.

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.