B737-800
Communication Breakdown; Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Procedure
When testing crew oxygen and mask on preflight; the crew oxygen pressure gage dropped from 1;200 PSI to 700 PSI. When oxygen switch was released crew oxygen gage returned to 1;200 PSI. This was true for both the Captain's and First Officer's masks. I called Maintenance and was informed that this is a 'regular occurrence' when an airplane comes from the Maintenance Center hangar. The reason this for this is; while the aircraft is in the hangar; it is routine for the crew oxygen cylinder to be wired shut; and often it leaves the hangar still wired shut. The mechanics at the gate knew exactly what it was and confirmed this with the flight crew.I feel this was too casual an approach concerning a piece of equipment that would be critical during abnormal procedures. My suggestion is to ensure that no aircraft leaves any Maintenance hangar with its crew oxygen bottle wired closed.
When the B737-800 flight crew advised Maintenance the crew oxygen test was abnormal they were advised the aircraft had just come from service where the crew O2 bottle is frequently wired closed. They were further advised it was not uncommon for it not to be reopened following maintenance. The First Officer suggested such casual disregard of an important aircraft safety system's availability during an emergency was not appropriate.