Flight crew of an MD80 executed an emergency descent and returned to land due to pressurization malf...

Attributes
ACN	464880
Time
Date	200002
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : lit.airport
State Reference	AR
Altitude	msl single value : 25000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zme.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute airway : j101.airway
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 16000 flight time type : 1900
ASRS Report	464880
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : aircraft pressurization indicator other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist flight crew : landed as precaution flight crew : exited adverse environment flight crew : declared emergency
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Aircraft was dispatched on MEL with left air conditioning pack inoperative. Per MEL, cruise was at FL250. Cabin got slightly cool, flight attendants asked for more heat. We set the cabin temperature controller to slightly warmer position in the automatic range. We suddenly had an uncontrollable cabin climb. In attempting to stop the cabin, we determined that the right pack had shut down with a high supply duct temperature. We believe that the automatic control failed and drove to a pack overheat. We asked and got a low altitude -- first 13000 ft, then 10000 ft. I performed an emergency descent maneuver and got to a lower altitude with the cabin rising to 10000-11000 ft. After troubleshooting, we re-established the right pack at 10000 ft. The pack did not seem normal though, we landed in lit after checking with company operations. I don't like 1 pack operations (though a legal dispatch). This appeared to be an unforeseen mechanical (or electrical) failure of the remaining pack.

Original NASA ASRS Text

Title: FLC OF AN MD80 EXECUTED AN EMER DSCNT AND RETURNED TO LAND DUE TO PRESSURIZATION MALFUNCTIONING.

Narrative: ACFT WAS DISPATCHED ON MEL WITH L AIR CONDITIONING PACK INOP. PER MEL, CRUISE WAS AT FL250. CABIN GOT SLIGHTLY COOL, FLT ATTENDANTS ASKED FOR MORE HEAT. WE SET THE CABIN TEMP CONTROLLER TO SLIGHTLY WARMER POS IN THE AUTO RANGE. WE SUDDENLY HAD AN UNCTLABLE CABIN CLB. IN ATTEMPTING TO STOP THE CABIN, WE DETERMINED THAT THE R PACK HAD SHUT DOWN WITH A HIGH SUPPLY DUCT TEMP. WE BELIEVE THAT THE AUTO CTL FAILED AND DROVE TO A PACK OVERHEAT. WE ASKED AND GOT A LOW ALT -- FIRST 13000 FT, THEN 10000 FT. I PERFORMED AN EMER DSCNT MANEUVER AND GOT TO A LOWER ALT WITH THE CABIN RISING TO 10000-11000 FT. AFTER TROUBLESHOOTING, WE RE-ESTABLISHED THE R PACK AT 10000 FT. THE PACK DID NOT SEEM NORMAL THOUGH, WE LANDED IN LIT AFTER CHKING WITH COMPANY OPS. I DON'T LIKE 1 PACK OPS (THOUGH A LEGAL DISPATCH). THIS APPEARED TO BE AN UNFORESEEN MECHANICAL (OR ELECTRICAL) FAILURE OF THE REMAINING PACK.

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.

Flight crew of an MD80 executed an emergency descent and returned to land due to pressurization malfunctioning.