MD80 experiences loss of cabin pressure at 30000 ft. Flight crew declares an emergency and diverts.

Attributes
ACN	731363
Time
Date	200703
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 30000
Environment
Weather Elements	Thunderstorm
Aircraft 1
Controlling Facilities	artcc : zzz.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	climbout : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	731363
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : cabin alt indicator other flight crewa other flight crewb
Resolutory Action	flight crew : diverted to another airport flight crew : declared emergency
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Dispatched to fly ship with 1 pack inoperative. Took off and was given vectors around a line of WX. Normal pressurization schedule through 10000 ft and 18000 ft. Cleared to our final cruising altitude; we had to put wing and engine heat on at around 20000 ft for IMC conditions during our climb. At about 25000 ft I noticed our pressurization was slightly off schedule on the high side. So we carefully monitored the system since a 1 pack operation (though it saves the company money) is not normal. At about 30000 ft we determined that the remaining pack was slowly failing us so we arrested the climb and coordinated a descent with ATC. As we began descending; we got the cabin altitude warnings. We initiated the loss of cabin pressure procedures; declared an emergency and diverted without further problems.

Original NASA ASRS Text

Title: MD80 EXPERIENCES LOSS OF CABIN PRESSURE AT 30000 FT. FLT CREW DECLARES AN EMER AND DIVERTS.

Narrative: DISPATCHED TO FLY SHIP WITH 1 PACK INOP. TOOK OFF AND WAS GIVEN VECTORS AROUND A LINE OF WX. NORMAL PRESSURIZATION SCHEDULE THROUGH 10000 FT AND 18000 FT. CLRED TO OUR FINAL CRUISING ALT; WE HAD TO PUT WING AND ENG HEAT ON AT AROUND 20000 FT FOR IMC CONDITIONS DURING OUR CLB. AT ABOUT 25000 FT I NOTICED OUR PRESSURIZATION WAS SLIGHTLY OFF SCHEDULE ON THE HIGH SIDE. SO WE CAREFULLY MONITORED THE SYS SINCE A 1 PACK OP (THOUGH IT SAVES THE COMPANY MONEY) IS NOT NORMAL. AT ABOUT 30000 FT WE DETERMINED THAT THE REMAINING PACK WAS SLOWLY FAILING US SO WE ARRESTED THE CLB AND COORDINATED A DSCNT WITH ATC. AS WE BEGAN DSNDING; WE GOT THE CABIN ALT WARNINGS. WE INITIATED THE LOSS OF CABIN PRESSURE PROCS; DECLARED AN EMER AND DIVERTED WITHOUT FURTHER PROBS.

Data retrieved from NASA's ASRS site as of January 2009 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.