Narrative:

I; [technician X;] was called into the manager's office late morning january 2015 and was informed [that] in december 2014; on a B737-900 aircraft; I documented crew oxygen low in logbook and it was reported approximately ten days later in logbook that the crew oxy failed the operational (ops) check by [flight] crew reading zero (0) psi. I performed [the crew oxygen servicing] task according to MM 12-15-21 and the supplemental job card. Technician Y performed the ops check and installation of the crew oxy [bottle]. While accomplishing the task we verified that there were no abnormalities. This task was accomplished by the book and documented as such. Crew performed ops checks numerous times per the company flight manual section (basically the same test we performed) and checked good. Between the time of servicing and the time of failing the test; approximately 46 flights [had occurred before] oxygen dropped to 0 psi. This verifies that I did this task according to job card; or it should have been detected the very next flight due to the fact that I did the 02 servicing on a routine overnight (ron) maintenance check and the first flight of the day O2 mask test would have failed. I'm not sure why this event happened! I performed crew servicing per MM 12-15-21; ops ck. And installation of crew oxygen verified not only by technician Y; but also pressure test was performed by numerous flight crews every day for 11 days and checked good and then drops to 0 psi. I feel I did nothing wrong. Graveyard. [Found] on preflight 11 days after I performed servicing.

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Original NASA ASRS Text

Title: Two Aircraft Maintenance Technicians (AMTs) describe their involvement with servicing crew oxygen on a B737-900 aircraft after a flight crew noted the cockpit O2 mask check had failed. Aircraft had been in service for 11 days and 46 flights before the O2 pressure had dropped to Zero (0) psi.

Narrative: I; [Technician X;] was called into the manager's office late morning January 2015 and was informed [that] in December 2014; on a B737-900 aircraft; I documented crew oxygen low in logbook and it was reported approximately ten days later in logbook that the crew oxy failed the operational (ops) check by [Flight] crew reading zero (0) psi. I performed [the Crew oxygen servicing] task according to MM 12-15-21 and the supplemental Job Card. Technician Y performed the ops check and installation of the Crew Oxy [bottle]. While accomplishing the task we verified that there were no abnormalities. This task was accomplished by the book and documented as such. Crew performed ops Checks numerous times per the Company flight manual Section (basically the same test we performed) and checked good. Between the time of servicing and the time of failing the test; approximately 46 flights [had occurred before] Oxygen Dropped to 0 psi. This verifies that I did this task according to Job Card; or it should have been detected the very next flight due to the fact that I did the 02 servicing on a Routine Overnight (RON) Maintenance Check and the first flight of the day O2 Mask test would have failed. I'm not sure why this event happened! I performed crew servicing per MM 12-15-21; Ops ck. and installation of crew oxygen verified not only by Technician Y; but also pressure test was performed by numerous flight crews every day for 11 days and checked good and then drops to 0 psi. I feel I did nothing wrong. Graveyard. [Found] on preflight 11 days after I performed servicing.

Data retrieved from NASA's ASRS site 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.