<< >> NASA ASRS Report 802175, August 2008

A B747-400 departing vhhh experienced loss of left pressure outflow valve. The reporter stated the problem had been cleared by vhhh maintenance but was still an issue. He coordinated with maintenance and continued.

Attributes
ACN	802175
Time
Date	200808
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : vhhh.airport
State Reference	FO
Altitude	msl single value : 2000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Flight Phase	climbout : initial
Route In Use	departure sid : sandi
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 240 flight time total : 15000 flight time type : 2500
ASRS Report	802175
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Supplementary
Problem Areas	Maintenance Human Performance Aircraft
Primary Problem	Ambiguous

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.