Air carrier medium large transport experiences loss of cabin pressure and methods of control.

Attributes
ACN	177589
Time
Date	199104
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mco
State Reference	FL
Altitude	msl bound lower : 7000 msl bound upper : 17000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : gsb
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other
Route In Use	enroute airway : zjx
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : cfi pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 180 flight time total : 10000 flight time type : 750
ASRS Report	177589
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : declared emergency flight crew : exited adverse environment other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

While en route from tlh to mco at 17000' MSL, the cabin altitude began climbing. It remained unnoticed until about 13000'. The passenger O2 masks dropped at 13500'. By that time we had begun a descent down to 7000' MSL. The cabin pressurization was uncontrollable and was fluctuating. The cabin seemed to follow the aircraft's rate of descent. Could not be controled from the cockpit. After recycling the bleed switches, the aircraft cabin altitude seemed to be ctlable for a brief period, then uncontrollable again. We depressurized the aircraft and landed in mco.

Original NASA ASRS Text

Title: ACR MLG EXPERIENCES LOSS OF CABIN PRESSURE AND METHODS OF CTL.

Narrative: WHILE ENRTE FROM TLH TO MCO AT 17000' MSL, THE CABIN ALT BEGAN CLBING. IT REMAINED UNNOTICED UNTIL ABOUT 13000'. THE PAX O2 MASKS DROPPED AT 13500'. BY THAT TIME WE HAD BEGUN A DSNT DOWN TO 7000' MSL. THE CABIN PRESSURIZATION WAS UNCTLABLE AND WAS FLUCTUATING. THE CABIN SEEMED TO FOLLOW THE ACFT'S RATE OF DSNT. COULD NOT BE CTLED FROM THE COCKPIT. AFTER RECYCLING THE BLEED SWITCHES, THE ACFT CABIN ALT SEEMED TO BE CTLABLE FOR A BRIEF PERIOD, THEN UNCTLABLE AGAIN. WE DEPRESSURIZED THE ACFT AND LANDED IN MCO.

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.