Four days after servicing a B737-900 cockpit crew O2 bottle; a mechanic was informed the bottle disc...

Narrative:

When I was performing a service check on a B737-900 aircraft; I found the crew O2 [pressure] is at 'below normal'. Per the service task card; I serviced it to full. After connecting the 'B' nut and performing a leak check; I discovered a leak at the 'B' nut. I repaired the leak by replacing the union assembly. After installing a new union assembly; the leak disappeared. Then I proceeded to install the discharge fitting and reconnect the overboard discharge line when I got called out to help someone else. When I came back to my work area; I quickly verified the valve on the [oxygen] bottle that [it] is in an 'open' position and its safety wired. The airplane needs to be moved right away because it's blocking another airplane that needs to be moved to the gate. I rushed to close the panel and the ground power was already disconnected. I used maintenance manuals (M/M) 12-15-21 and 35-12-11 for my reference. I got called out by a fellow technician for help during installation. The B737-900 needed to be moved because it was blocking an airplane that is ready to be moved to its gate. A fellow technician found the problem while servicing the crew O2 bottle. If a technician is interrupted while doing his or her work; he or she must go over the repair process from the beginning of the manual.

Original NASA ASRS Text

Title: Four days after servicing a B737-900 cockpit Crew O2 bottle; a Mechanic was informed the bottle discharge line to the fuselage overboard connector was found loose.

Narrative: When I was performing a Service Check on a B737-900 aircraft; I found the Crew O2 [pressure] is at 'below normal'. Per the Service Task Card; I serviced it to full. After connecting the 'B' nut and performing a leak check; I discovered a leak at the 'B' nut. I repaired the leak by replacing the union assembly. After installing a new union assembly; the leak disappeared. Then I proceeded to install the discharge fitting and reconnect the overboard discharge line when I got called out to help someone else. When I came back to my work area; I quickly verified the valve on the [Oxygen] bottle that [it] is in an 'Open' position and its safety wired. The airplane needs to be moved right away because it's blocking another airplane that needs to be moved to the gate. I rushed to close the panel and the Ground Power was already disconnected. I used Maintenance Manuals (M/M) 12-15-21 and 35-12-11 for my reference. I got called out by a fellow Technician for help during installation. The B737-900 needed to be moved because it was blocking an airplane that is ready to be moved to its gate. A fellow Technician found the problem while servicing the Crew O2 bottle. If a Technician is interrupted while doing his or her work; he or she must go over the repair process from the beginning of the manual.

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	972590
Time
Date	201109
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Night
Aircraft 1
Make Model Name	B737-900
Operating Under FAR Part	Part 121
Flight Phase	Parked
Component
Aircraft Component	Oxygen System/Crew
Person 1
Function	Technician
Qualification	Maintenance Airframe Maintenance Powerplant
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

Four days after servicing a B737-900 cockpit crew O2 bottle; a mechanic was informed the bottle discharge line to the fuselage overboard connector was found loose.