B737-800
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Training / Qualification
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Manuals; Human Factors; Equipment / Tooling; Aircraft
As I was testing my oxygen mask; while looking at the Crew Oxygen Pressure; I observed the pressure drop from 1;870 PSI to 1;800 PSI in about 10-seconds and not recover. A second test resulted in a similar result: the Crew Oxygen Pressure dropped and did not recover. Maintenance was notified and discovered the Crew Oxygen Bottle Valve was not fully open. The valve was fully opened and safety wired by Maintenance. Crew Oxygen Pressure did not drop during subsequent tests of my oxygen mask. As the Crew Oxygen Bottle Pressure was about 1;900 PSI at the start of my first mask test; I suspect the oxygen bottle was recently installed. Ensure all maintainers are familiar with the proper procedure for B737 Crew Oxygen Bottle installation.
While performing a Crew Oxygen Mask Check on a B737-800 aircraft; a Captain observed the Crew Oxygen Pressure drop from 1;870 PSI down to 1;800 PSI in about 10-seconds and not recover. Maintenance found the Crew Oxygen Bottle Valve not fully opened.