Medium large transport at cruise has caution light on the pressurization system activate.

Attributes
ACN	243757
Time
Date	199306
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : bna
State Reference	TN
Altitude	msl bound lower : 10000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme
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 : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : flight engineer pilot : instrument pilot : atp pilot : cfi
Experience	flight time last 90 days : 140 flight time total : 10000
ASRS Report	243757
Person 2
Function	flight crew : captain oversight : pic
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 other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

On flight pit to dfw at FL350 I noticed we were getting into icing conditions. Looking up to see if it was on I noticed the caution light on the pressurization system. I brought it to the captain's attention and started working on the abnormal checklist. We could not arrest the pressurization before 10000 ft cabin altitude then moved on to the explosive depressurization procedure and the emergency descent procedure. Set 7700 in the transponder and got clearance to 10000 with a turn to nashville. In nashville, the WX was VFR. Landing safely with emergency equipment standing by. No passenger injured. The system of checklists and help with ATC worked very well. Probable cause was failure of the air conditioning system.

Original NASA ASRS Text

Title: MLG AT CRUISE HAS CAUTION LIGHT ON THE PRESSURIZATION SYS ACTIVATE.

Narrative: ON FLT PIT TO DFW AT FL350 I NOTICED WE WERE GETTING INTO ICING CONDITIONS. LOOKING UP TO SEE IF IT WAS ON I NOTICED THE CAUTION LIGHT ON THE PRESSURIZATION SYS. I BROUGHT IT TO THE CAPT'S ATTN AND STARTED WORKING ON THE ABNORMAL CHKLIST. WE COULD NOT ARREST THE PRESSURIZATION BEFORE 10000 FT CABIN ALT THEN MOVED ON TO THE EXPLOSIVE DEPRESSURIZATION PROC AND THE EMER DSCNT PROC. SET 7700 IN THE XPONDER AND GOT CLRNC TO 10000 WITH A TURN TO NASHVILLE. IN NASHVILLE, THE WX WAS VFR. LNDG SAFELY WITH EMER EQUIP STANDING BY. NO PAX INJURED. THE SYS OF CHKLISTS AND HELP WITH ATC WORKED VERY WELL. PROBABLE CAUSE WAS FAILURE OF THE AIR CONDITIONING SYS.

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.