Large transport made emergency descent when cabin pressurization system failed.

Attributes
ACN	96443
Time
Date	198810
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : orl airport : fll
State Reference	FL
Altitude	msl bound lower : 37000 msl bound upper : 37000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tower : ord
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute airway : j53
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 6800
ASRS Report	96443
Person 2
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 4500
ASRS Report	96442
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

After reaching cruising altitude at FL370 and with a satisfactory cabin altitude at the time of 6300', the cabin started an abrupt climb at a rate of 1500-2000 FPM. Suspecting a failure on the pressurization 'automatic mode,' the system controller was switched to 'standby mode' with negative result. The outflow valve was manually closed at this time, however, the cabin continued climbing rapidly out of normal parameters. ATC was notified of the problem and an emergency descent to 10000' was executed. The passenger oxygen masks dropped properly at a cabin altitude of 14000'. ATC gave us vectors to fll (our airport of departure) and a normal approach and landing was accomplished. All emergency and normal checklists were done and completed throughout the flight. Upon landing in fll no passenger or crew members reported medical problems.

Original NASA ASRS Text

Title: LGT MADE EMERGENCY DESCENT WHEN CABIN PRESSURIZATION SYSTEM FAILED.

Narrative: AFTER REACHING CRUISING ALT AT FL370 AND WITH A SATISFACTORY CABIN ALT AT THE TIME OF 6300', THE CABIN STARTED AN ABRUPT CLB AT A RATE OF 1500-2000 FPM. SUSPECTING A FAILURE ON THE PRESSURIZATION 'AUTO MODE,' THE SYS CTLR WAS SWITCHED TO 'STANDBY MODE' WITH NEGATIVE RESULT. THE OUTFLOW VALVE WAS MANUALLY CLOSED AT THIS TIME, HOWEVER, THE CABIN CONTINUED CLBING RAPIDLY OUT OF NORMAL PARAMETERS. ATC WAS NOTIFIED OF THE PROB AND AN EMER DSCNT TO 10000' WAS EXECUTED. THE PAX OXYGEN MASKS DROPPED PROPERLY AT A CABIN ALT OF 14000'. ATC GAVE US VECTORS TO FLL (OUR ARPT OF DEP) AND A NORMAL APCH AND LNDG WAS ACCOMPLISHED. ALL EMER AND NORMAL CHKLISTS WERE DONE AND COMPLETED THROUGHOUT THE FLT. UPON LNDG IN FLL NO PAX OR CREW MEMBERS REPORTED MEDICAL PROBS.

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.