A mechanic reports about a B777-200 returning to field for pressurization problems after missing a s...

Narrative:

Aircraft X arrived with a central maintenance computer and a log write-up 'outflow valve aft.' after aircraft maintenance history review; I elected to defer this discrepancy under MEL 21-31S. The aircraft departed ZZZ as scheduled; however; the aircraft returned to ZZZ shortly thereafter with problems related to pressurization. After learning that the aircraft was returning with a problem related to maintenance actions I performed; I reviewed the MEL procedure that I performed. I missed a step within the procedure that required the left aft outflow valve circuit breaker be pulled and collared along with the right; I only accomplished this for the right circuit breaker. I believe my error led to the return to the field.

Original NASA ASRS Text

Title: A Mechanic reports about a B777-200 returning to field for pressurization problems after missing a step in the MEL procedure to also pull and collar the left aft outflow valve circuit breaker.

Narrative: Aircraft X arrived with a central maintenance computer and a log write-up 'Outflow Valve Aft.' After aircraft maintenance history review; I elected to defer this discrepancy under MEL 21-31S. The aircraft departed ZZZ as scheduled; however; the aircraft returned to ZZZ shortly thereafter with problems related to pressurization. After learning that the aircraft was returning with a problem related to maintenance actions I performed; I reviewed the MEL procedure that I performed. I missed a step within the procedure that required the left aft outflow valve CB be pulled and collared along with the right; I only accomplished this for the right CB. I believe my error led to the return to the field.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	823284
Time
Date	200902
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	B777-200
Operating Under FAR Part	Part 121
Flight Phase	Parked
Component
Aircraft Component	Pressurization Outflow Valve
Person 1
Function	Technician
Person 2
Function	Captain
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural FAR Deviation - Procedural MEL Deviation - Procedural Maintenance Deviation - Procedural Published Material / Policy

A mechanic reports about a B777-200 returning to field for pressurization problems after missing a step in the MEL procedure to also pull and collar the left aft outflow valve circuit breaker.