A B737-200 in cruise at FL310 declared an emergency and diverted due to the loss of cabin pressure c...

Attributes
ACN	412673
Time
Date	199808
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : irw
State Reference	OK
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zfw
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	Part 121
Flight Phase	cruise other other other
Route In Use	enroute airway : zfw
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 20000 flight time type : 4500
ASRS Report	412673
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : declared emergency none taken : detected after the fact other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

En route from atl to phx the crew discovered that the cabin was climbing at approximately 100 FPM and the cabin was just barely over 9000 ft. It should have been at 4100 ft. I called for the loss of pressurization checklist. All items were completed but cabin was still climbing at 100 FPM. The intermittent pressurization horn went off and I initiated an emergency descent to 10000 ft and received vectors from ATC for direct dfw as this is a large air carrier hub and a good place for repairs and passenger handling. We landed dfw at XA00 and ended up canceling the flight. The passenger were put on another carrier and our aircraft taken to the hangar for repairs. We did declare an emergency to dfw ATC. Callback conversation with reporter revealed the following information: the reporter stated when looking at the pressurization panel it was noted the cabin had climbed to 9000 ft and slowly increased 100 FPM. The reporter said an emergency descent was made and advised ATC of need to divert to dfw. The reporter stated the cause of the pressure problem was the radio rack cooling outflow valve which is normally closed to allow warm air heated from the electronic equipment to heat the forward cargo compartment. The reporter said this valve was cracked open enough to allow the cabin to climb 100 FPM.

Original NASA ASRS Text

Title: A B737-200 IN CRUISE AT FL310 DECLARED AN EMER AND DIVERTED DUE TO THE LOSS OF CABIN PRESSURE CAUSED BY A PARTIALLY OPEN RADIO RACK COOLING OUTFLOW VALVE.

Narrative: ENRTE FROM ATL TO PHX THE CREW DISCOVERED THAT THE CABIN WAS CLBING AT APPROX 100 FPM AND THE CABIN WAS JUST BARELY OVER 9000 FT. IT SHOULD HAVE BEEN AT 4100 FT. I CALLED FOR THE LOSS OF PRESSURIZATION CHKLIST. ALL ITEMS WERE COMPLETED BUT CABIN WAS STILL CLBING AT 100 FPM. THE INTERMITTENT PRESSURIZATION HORN WENT OFF AND I INITIATED AN EMER DSCNT TO 10000 FT AND RECEIVED VECTORS FROM ATC FOR DIRECT DFW AS THIS IS A LARGE ACR HUB AND A GOOD PLACE FOR REPAIRS AND PAX HANDLING. WE LANDED DFW AT XA00 AND ENDED UP CANCELING THE FLT. THE PAX WERE PUT ON ANOTHER CARRIER AND OUR ACFT TAKEN TO THE HANGAR FOR REPAIRS. WE DID DECLARE AN EMER TO DFW ATC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED WHEN LOOKING AT THE PRESSURIZATION PANEL IT WAS NOTED THE CABIN HAD CLBED TO 9000 FT AND SLOWLY INCREASED 100 FPM. THE RPTR SAID AN EMER DSCNT WAS MADE AND ADVISED ATC OF NEED TO DIVERT TO DFW. THE RPTR STATED THE CAUSE OF THE PRESSURE PROB WAS THE RADIO RACK COOLING OUTFLOW VALVE WHICH IS NORMALLY CLOSED TO ALLOW WARM AIR HEATED FROM THE ELECTRONIC EQUIP TO HEAT THE FORWARD CARGO COMPARTMENT. THE RPTR SAID THIS VALVE WAS CRACKED OPEN ENOUGH TO ALLOW THE CABIN TO CLB 100 FPM.

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.

A B737-200 in cruise at FL310 declared an emergency and diverted due to the loss of cabin pressure caused by a partially open radio rack cooling outflow valve.