Narrative:

During climb out from vhhh; the left pressurization outflow valve failed. This is a repeat failure from the last leg. As always; maintenance found nothing wrong after the first write-up and cleared the item. I accomplished the irregular procedure while the first officer flew and handled the radios. Workload was high given the high terrain; nighttime; numerous ATC vectors and instructions; and the WX. The valve had failed at about 25% open position and pressurization could not be maintained until the valve was manually closed per the procedure. I contacted maintenance through dispatch and elected to continue the flight at a lower altitude (FL320 versus FL390).

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Original NASA ASRS Text

Title: A B747-400 DEPARTING VHHH EXPERIENCED LOSS OF L PRESSURE OUTFLOW VALVE. THE REPORTER STATED THE PROBLEM HAD BEEN CLEARED BY VHHH MAINT BUT WAS STILL AN ISSUE. HE COORDINATED WITH MAINT AND CONTINUED.

Narrative: DURING CLBOUT FROM VHHH; THE L PRESSURIZATION OUTFLOW VALVE FAILED. THIS IS A REPEAT FAILURE FROM THE LAST LEG. AS ALWAYS; MAINT FOUND NOTHING WRONG AFTER THE FIRST WRITE-UP AND CLRED THE ITEM. I ACCOMPLISHED THE IRREGULAR PROC WHILE THE FO FLEW AND HANDLED THE RADIOS. WORKLOAD WAS HIGH GIVEN THE HIGH TERRAIN; NIGHTTIME; NUMEROUS ATC VECTORS AND INSTRUCTIONS; AND THE WX. THE VALVE HAD FAILED AT ABOUT 25% OPEN POS AND PRESSURIZATION COULD NOT BE MAINTAINED UNTIL THE VALVE WAS MANUALLY CLOSED PER THE PROC. I CONTACTED MAINT THROUGH DISPATCH AND ELECTED TO CONTINUE THE FLT AT A LOWER ALT (FL320 VERSUS FL390).

Data retrieved from NASA's ASRS site as of May 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.