MD80 crew made emergency descent after cabin pressurization was lost.

Attributes
ACN	441608
Time
Date	199907
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : ukw.vortac
State Reference	TX
Altitude	msl single value : 29000
Environment
Flight Conditions	IMC
Weather Elements	Ice
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zfw.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	441608
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
ASRS Report	441607
Events
Anomaly	aircraft equipment problem : critical inflight encounter : weather
Independent Detector	aircraft equipment other aircraft equipment : pressure alert light other flight crewa other flight crewb
Resolutory Action	flight crew : overcame equipment problem flight crew : declared emergency
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Loss of pressurization. Upon exiting icing conditions, I cycled the tail heat and turned off all the anti-icing. The cabin began an uncommanded climb of about 1000 FPM, with the pressure flow light on. We were at FL290 with a cabin altitude of about 6000 ft. We began a rapid descent and leveled off at 10000 ft. The air conditioning flow gauges indicated less than 9 O'clock position. No combination of standby or manual control restored pressure. I turned 1 engine anti-ice switch back on and both packs immediately produced flow greater than 12 O'clock position. I ran both engine anti-ice valves for a few moments and then turned all off. Pressure remained normal and flight was completed at 10000 ft except to enter the arrival at 11000 ft.

Original NASA ASRS Text

Title: MD80 CREW MADE EMER DSCNT AFTER CABIN PRESSURIZATION WAS LOST.

Narrative: LOSS OF PRESSURIZATION. UPON EXITING ICING CONDITIONS, I CYCLED THE TAIL HEAT AND TURNED OFF ALL THE ANTI-ICING. THE CABIN BEGAN AN UNCOMMANDED CLB OF ABOUT 1000 FPM, WITH THE PRESSURE FLOW LIGHT ON. WE WERE AT FL290 WITH A CABIN ALT OF ABOUT 6000 FT. WE BEGAN A RAPID DSCNT AND LEVELED OFF AT 10000 FT. THE AIR CONDITIONING FLOW GAUGES INDICATED LESS THAN 9 O'CLOCK POS. NO COMBINATION OF STANDBY OR MANUAL CTL RESTORED PRESSURE. I TURNED 1 ENG ANTI-ICE SWITCH BACK ON AND BOTH PACKS IMMEDIATELY PRODUCED FLOW GREATER THAN 12 O'CLOCK POS. I RAN BOTH ENG ANTI-ICE VALVES FOR A FEW MOMENTS AND THEN TURNED ALL OFF. PRESSURE REMAINED NORMAL AND FLT WAS COMPLETED AT 10000 FT EXCEPT TO ENTER THE ARR AT 11000 FT.

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.