B777-200 crew was unable to pressurize the aircraft. One outflow valve was MEL'ed inoperative.

Attributes
ACN	603057
Time
Date	200312
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : egtt.artcc
State Reference	FO
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : egtt.artcc
Operator	common carrier : air carrier
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	603057
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical maintenance problem : improper maintenance maintenance problem : non compliance with mel non adherence : company policies non adherence : published procedure non adherence : far
Independent Detector	aircraft equipment other aircraft equipment : cabin differential pressure, cabin altitude other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance controller : provided flight assist flight crew : diverted to another airport flight crew : landed as precaution none taken : detected after the fact other
Consequence	other other other
Factors
Maintenance	contributing factor : schedule pressure performance deficiency : non compliance with legal requirements
Supplementary
Problem Areas	Maintenance Human Performance Aircraft Company
Primary Problem	Maintenance Human Performance

Narrative:

Air interruption. Cabin pressurization became uncontrollable during climb out from lhr. Declared an emergency to facilitate an emergency descent to 10000 ft and diverted back to lhr. After ATC was notified, we dumped fuel to preclude an overweight landing. Landing was uneventful. Callback conversation with reporter revealed the following information: the aircraft was dispatched with 1 outflow valve MEL'ed inoperative. The MEL requires the inoperative outflow valve be deactivated in an almost closed position. The outflow valve was actually deactivated open. The crew was assigned to ferry the aircraft across the atlantic the next day. The reporter noted that the outflow valve controller was replaced. The deferred item was cleared and the aircraft operated normally.

Original NASA ASRS Text

Title: B777-200 CREW WAS UNABLE TO PRESSURIZE THE ACFT. ONE OUTFLOW VALVE WAS MEL'ED INOP.

Narrative: AIR INTERRUPTION. CABIN PRESSURIZATION BECAME UNCTLABLE DURING CLBOUT FROM LHR. DECLARED AN EMER TO FACILITATE AN EMER DSCNT TO 10000 FT AND DIVERTED BACK TO LHR. AFTER ATC WAS NOTIFIED, WE DUMPED FUEL TO PRECLUDE AN OVERWT LNDG. LNDG WAS UNEVENTFUL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE ACFT WAS DISPATCHED WITH 1 OUTFLOW VALVE MEL'ED INOP. THE MEL REQUIRES THE INOP OUTFLOW VALVE BE DEACTIVATED IN AN ALMOST CLOSED POS. THE OUTFLOW VALVE WAS ACTUALLY DEACTIVATED OPEN. THE CREW WAS ASSIGNED TO FERRY THE ACFT ACROSS THE ATLANTIC THE NEXT DAY. THE RPTR NOTED THAT THE OUTFLOW VALVE CONTROLLER WAS REPLACED. THE DEFERRED ITEM WAS CLRED AND THE ACFT OPERATED NORMALLY.

Data retrieved from NASA's ASRS site as of July 2007 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.