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A B737-800 flight crew flew two legs before discovering their flight crew oxygen bottle pressure well below minimum upon completion of their final leg. The pressure gauge had been reading abnormally high which did not trigger further assessment earlier.
| Attributes | |
| ACN | 1086358 |
| Time | |
| Date | 201305 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Aircraft 1 | |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Parked |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Oxygen System/Crew |
| Person 1 | |
| Function | Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical |
Narrative:
During preflight for our first two legs both of us noticed the crew O2 was pegged past full which; in retrospect; looked out of the ordinary but neither of us mentioned it to the other. We ended up diverting to ontario on our last leg due to weather at our destination. On the post flight we noticed the crew O2 was now pegged in the other direction; low; and called maintenance. The mechanic said there was a loose connection; possibly the cannon plug; for the cockpit indicator and that the actual bottle pressure was 300 psi which was well below the 1;000 psi minimum. To me; it appeared the airplane had flown for some period of time with significantly low flight crew O2 that was unknown to the pilots due to a faulty gauge. Had a situation occurred where we needed the oxygen it might have been a problem. I suggest putting some information out to line pilots about what a faulty crew O2 indication might look like; i.e. Fully pegged past full and how often the crew bottle pressure is checked by maintenance. This may just have been a random event but if it happened once it could happen again.
Original NASA ASRS Text
Title: A B737-800 flight crew flew two legs before discovering their flight crew oxygen bottle pressure well below minimum upon completion of their final leg. The pressure gauge had been reading abnormally high which did not trigger further assessment earlier.
Narrative: During preflight for our first two legs both of us noticed the crew O2 was pegged past full which; in retrospect; looked out of the ordinary but neither of us mentioned it to the other. We ended up diverting to Ontario on our last leg due to weather at our destination. On the post flight we noticed the crew O2 was now pegged in the other direction; low; and called maintenance. The mechanic said there was a loose connection; possibly the cannon plug; for the cockpit indicator and that the actual bottle pressure was 300 PSI which was well below the 1;000 PSI minimum. To me; it appeared the airplane had flown for some period of time with significantly low flight crew O2 that was unknown to the pilots due to a faulty gauge. Had a situation occurred where we needed the oxygen it might have been a problem. I suggest putting some information out to line pilots about what a faulty crew O2 indication might look like; i.e. fully pegged past full and how often the crew bottle pressure is checked by maintenance. This may just have been a random event but if it happened once it could happen again.
Data retrieved from NASA's ASRS site as of July 2013 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.