Air carrier flight crew unable to maintain cabin pressurization. Unable callback.

Attributes
ACN	146262
Time
Date	199005
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : air
State Reference	OH
Altitude	msl bound lower : 11000 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other descent other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time total : 15000
ASRS Report	146262
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : declared emergency flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

Excessive cabin pressure altitude indicated by computer warning and systems indicator. Was able to control cabin to 10000'. Our cruise altitude was FL290. Requested and received ATC rapid descent to 11000' and was able to lower cabin to 8000', but no lower. Attempted to xfer automatic control system to standby system, but was unable. Went to manual control, but could only achieve 8000' (cabin altitude). Requested and received ATC permission for gradual descent from 11000' until landing at 500 FPM, due to pressure effect on passenger in descent. Flight terminated west/O further event. On this computer controled aircraft, if the computer decides to render a system inoperative, there is no manual way to override the computer!

Original NASA ASRS Text

Title: ACR FLT CREW UNABLE TO MAINTAIN CABIN PRESSURIZATION. UNABLE CALLBACK.

Narrative: EXCESSIVE CABIN PRESSURE ALT INDICATED BY COMPUTER WARNING AND SYSTEMS INDICATOR. WAS ABLE TO CTL CABIN TO 10000'. OUR CRUISE ALT WAS FL290. REQUESTED AND RECEIVED ATC RAPID DSNT TO 11000' AND WAS ABLE TO LOWER CABIN TO 8000', BUT NO LOWER. ATTEMPTED TO XFER AUTO CTL SYS TO STANDBY SYS, BUT WAS UNABLE. WENT TO MANUAL CTL, BUT COULD ONLY ACHIEVE 8000' (CABIN ALT). REQUESTED AND RECEIVED ATC PERMISSION FOR GRADUAL DSNT FROM 11000' UNTIL LNDG AT 500 FPM, DUE TO PRESSURE EFFECT ON PAX IN DSNT. FLT TERMINATED W/O FURTHER EVENT. ON THIS COMPUTER CTLED ACFT, IF THE COMPUTER DECIDES TO RENDER A SYS INOP, THERE IS NO MANUAL WAY TO OVERRIDE THE COMPUTER!

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.