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A trans pacific B747-400 fight diverted to a domestic station for maintenance when the crew oxygen was decreasing below acceptable limits.
| Attributes | |
| ACN | 893439 |
| Time | |
| Date | 201006 |
| Local Time Of Day | 0001-0600 |
| Place | |
| Locale Reference | ZAN.ARTCC |
| State Reference | AK |
| Aircraft 1 | |
| Make Model Name | B747-400 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Climb |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Oxygen System/Crew |
| Person 1 | |
| Function | Captain Pilot Not Flying Check Pilot |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 255 Flight Crew Total 24000 Flight Crew Type 4500 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Inflight Event / Encounter Fuel Issue |
Narrative:
At deptarture we noticed the crew oxygen low 1500 psi and called maintenance. They were already aware and serviced it to 1750 psi. About 4 hours into the flight I noticed the pressure down to 1250 psi. We discussed with dispatch and with each other possible ways to avoid a divert but finally realized prior to entering russian airspace that we could not continue safely. The crew oxygen got down to 1130 psi prior to landing. We felt 950 was a safe level for two pilots; minus 350 psi for each empty jump seat. The EICAS does not monitor this pressure and it is on a page that is not normally displayed at cruise. My old flight engineer habit of routinely checking systems made us aware of this early but it would be easy to miss. We diverted to ZZZ at FL290 to avoid dumping fuel. We noticed that the leak rate did slow down at the lower altitude.
Original NASA ASRS Text
Title: A trans Pacific B747-400 fight diverted to a domestic station for maintenance when the crew oxygen was decreasing below acceptable limits.
Narrative: At deptarture we noticed the crew oxygen low 1500 PSI and called maintenance. They were already aware and serviced it to 1750 PSI. About 4 hours into the flight I noticed the pressure down to 1250 PSI. We discussed with Dispatch and with each other possible ways to avoid a divert but finally realized prior to entering Russian airspace that we could not continue safely. The crew oxygen got down to 1130 PSI prior to landing. We felt 950 was a safe level for two pilots; minus 350 PSI for each empty jump seat. The EICAS does not monitor this pressure and it is on a page that is not normally displayed at cruise. My old flight engineer habit of routinely checking systems made us aware of this early but it would be easy to miss. We diverted to ZZZ at FL290 to avoid dumping fuel. We noticed that the leak rate did slow down at the lower altitude.
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.