A B737 experienced pressurization problems; declared an emergency and returned to departure airport.

Attributes
ACN	715360
Time
Date	200610
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 24000
Environment
Flight Conditions	VMC
Weather Elements	other
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air carrier
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	715360
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 pressure gauge 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:

The captain and I reviewed the procedures for the pressurization MEL; verified correct operation of the outflow valve; completed our normal checklists and pushed. Aircraft was dispatched with one pressurization controller inoperative. During climb out at approximately FL240 it was noted that the cabin pressure differential was at redline and cabin altitude was at 'SL.' an immediate descent was requested and the appropriate checklists were followed. The cabin altitude was still at 'SL' and crew oxygen masks were prepared and used as a precaution. While descending the standby system did not respond to the descent so manual was selected; and cabin altitude control was regained. Passenger oxygen masks were not required or deployed. The passenger; crew; company and dispatch were notified of our intent to return to ZZZ. An emergency was declared for expeditious handling back to ZZZ. The return proceeded without further incident.

Original NASA ASRS Text

Title: A B737 EXPERIENCED PRESSURIZATION PROBS; DECLARED AN EMER AND RETURNED TO DEP ARPT.

Narrative: THE CAPT AND I REVIEWED THE PROCS FOR THE PRESSURIZATION MEL; VERIFIED CORRECT OP OF THE OUTFLOW VALVE; COMPLETED OUR NORMAL CHKLISTS AND PUSHED. ACFT WAS DISPATCHED WITH ONE PRESSURIZATION CTLR INOP. DURING CLBOUT AT APPROX FL240 IT WAS NOTED THAT THE CABIN PRESSURE DIFFERENTIAL WAS AT REDLINE AND CABIN ALT WAS AT 'SL.' AN IMMEDIATE DSCNT WAS REQUESTED AND THE APPROPRIATE CHKLISTS WERE FOLLOWED. THE CABIN ALT WAS STILL AT 'SL' AND CREW OXYGEN MASKS WERE PREPARED AND USED AS A PRECAUTION. WHILE DSNDING THE STANDBY SYS DID NOT RESPOND TO THE DSCNT SO MANUAL WAS SELECTED; AND CABIN ALT CTL WAS REGAINED. PAX OXYGEN MASKS WERE NOT REQUIRED OR DEPLOYED. THE PAX; CREW; COMPANY AND DISPATCH WERE NOTIFIED OF OUR INTENT TO RETURN TO ZZZ. AN EMER WAS DECLARED FOR EXPEDITIOUS HANDLING BACK TO ZZZ. THE RETURN PROCEEDED 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.