MD80 flight crew has a cabin pressurization problem; declares an emergency.

Attributes
ACN	699461
Time
Date	200606
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : zzz.artcc
State Reference	US
Altitude	msl single value : 24000
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	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	699461
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist flight crew : declared emergency flight crew : overcame equipment problem
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

In cruise at FL240; we felt a sudden; extreme pressurization change in our ears. Thinking we had an explosive depressurization; we donned oxygen masks and I selected manual pressurization as per the operations manual. I then requested lower; but was given only FL200; so I declared an emergency and informed ATC we would be descending to 10000 ft. During the descent; I determined that the pressurization controller had malfunctioned; but over-pressurized the aircraft; rather than losing pressurization. I then canceled the emergency with ATC; and proceeded to ZZZ without further incident.

Original NASA ASRS Text

Title: MD80 FLT CREW HAS A CABIN PRESSURIZATION PROB; DECLARES AN EMER.

Narrative: IN CRUISE AT FL240; WE FELT A SUDDEN; EXTREME PRESSURIZATION CHANGE IN OUR EARS. THINKING WE HAD AN EXPLOSIVE DEPRESSURIZATION; WE DONNED OXYGEN MASKS AND I SELECTED MANUAL PRESSURIZATION AS PER THE OPS MANUAL. I THEN REQUESTED LOWER; BUT WAS GIVEN ONLY FL200; SO I DECLARED AN EMER AND INFORMED ATC WE WOULD BE DSNDING TO 10000 FT. DURING THE DSCNT; I DETERMINED THAT THE PRESSURIZATION CONTROLLER HAD MALFUNCTIONED; BUT OVER-PRESSURIZED THE ACFT; RATHER THAN LOSING PRESSURIZATION. I THEN CANCELED THE EMER WITH ATC; AND PROCEEDED TO ZZZ WITHOUT FURTHER INCIDENT.

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.