An air carrier medium large transport made an emergency descent following loss of pressurization con...

Attributes
ACN	256663
Time
Date	199311
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sfo
State Reference	CA
Altitude	msl bound lower : 10000 msl bound upper : 22000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other other
Route In Use	enroute airway : zoa
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : commercial pilot : instrument pilot : flight engineer
Experience	flight time last 90 days : 200 flight time total : 4000 flight time type : 1700
ASRS Report	256663
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : atp pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 180 flight time total : 10000 flight time type : 4000
ASRS Report	256863
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : unable other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

During climb out at approximately 22000 ft we felt and saw the cabin climbing greater than 4000 FPM. We changed the pressurization controller to stand by and the cabin continued to climb uncontrollably. Manual pressurization also did not close the outflow valve. We notified ATC of our problem and started a descent to 12000 ft. At approximately 88 NM from sfo VOR we made the decision to return to san francisco. We were given a vector to intercept the big sur arrival to sfo and given a descent to 10000 ft. The continuing descent and approach was accomplished normally according to sops. Once on the ground, we ran a check of the pressurization system and found it to operate normally only in manual dc. The automatic and standby modes could not control the outflow value. The airplane was taken OTS. Supplemental information from acn 256863: the cabin altitude exceeded 14000 ft and the oxygen masks deployed before the aircraft altitude could be brought down. The crew took off their oxygen masks and returned the aircraft to sfo. Total flight time was 40 mins.

Original NASA ASRS Text

Title: AN ACR MLG MADE AN EMER DSCNT FOLLOWING LOSS OF PRESSURIZATION CTL.

Narrative: DURING CLBOUT AT APPROX 22000 FT WE FELT AND SAW THE CABIN CLBING GREATER THAN 4000 FPM. WE CHANGED THE PRESSURIZATION CTLR TO STAND BY AND THE CABIN CONTINUED TO CLB UNCONTROLLABLY. MANUAL PRESSURIZATION ALSO DID NOT CLOSE THE OUTFLOW VALVE. WE NOTIFIED ATC OF OUR PROB AND STARTED A DSCNT TO 12000 FT. AT APPROX 88 NM FROM SFO VOR WE MADE THE DECISION TO RETURN TO SAN FRANCISCO. WE WERE GIVEN A VECTOR TO INTERCEPT THE BIG SUR ARR TO SFO AND GIVEN A DSCNT TO 10000 FT. THE CONTINUING DSCNT AND APCH WAS ACCOMPLISHED NORMALLY ACCORDING TO SOPS. ONCE ON THE GND, WE RAN A CHK OF THE PRESSURIZATION SYS AND FOUND IT TO OPERATE NORMALLY ONLY IN MANUAL DC. THE AUTOMATIC AND STANDBY MODES COULD NOT CTL THE OUTFLOW VALUE. THE AIRPLANE WAS TAKEN OTS. SUPPLEMENTAL INFORMATION FROM ACN 256863: THE CABIN ALT EXCEEDED 14000 FT AND THE OXYGEN MASKS DEPLOYED BEFORE THE ACFT ALT COULD BE BROUGHT DOWN. THE CREW TOOK OFF THEIR OXYGEN MASKS AND RETURNED THE ACFT TO SFO. TOTAL FLT TIME WAS 40 MINS.

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.

An air carrier medium large transport made an emergency descent following loss of pressurization control.