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B767 captain reported discovering a crew oxygen issue during preflight that had been missed by multiple parties earlier.
| Attributes | |
| ACN | 1726240 |
| Time | |
| Date | 202002 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Make Model Name | B767 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Parked |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Oxygen System/Crew |
| Person 1 | |
| Function | Captain Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument |
| Experience | Flight Crew Last 90 Days 202 Flight Crew Total 12720 Flight Crew Type 808 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Deviation - Procedural Maintenance Deviation - Procedural Published Material / Policy |
Narrative:
During cockpit preflight checks; oxygen pressure read 1960 psi; but rapidly decreased to 70 psi when pushing and holding the oxygen mask emergency/test knob. After releasing the knob; pressure quickly returned to 1960 psi. Test returned same result on first officer (first officer) side. Submitted elb report and requested maintenance. When maintenance reported to the flight deck and I demonstrated a failed test; they said that it was ok because the pressure was returning to normal after the test. I explained our test parameters and requested that they check that the oxygen cylinder valve was fully open. Maintenance found the cylinder valve only partially opened. Once fully opened the valve and the system then checked normallywith the valve in the partially open position insufficient oxygen was available for breathing through the mask. The aircraft was released from maintenance in this condition; where mechanics preformed ETOPS checks and issued a [maintenance release]. There were at least 3 opportunities to discover this problem before the airplane flew; and an additional opportunity before I discovered the problem.
Original NASA ASRS Text
Title: B767 Captain reported discovering a crew oxygen issue during preflight that had been missed by multiple parties earlier.
Narrative: During cockpit preflight checks; oxygen pressure read 1960 psi; but rapidly decreased to 70 psi when pushing and holding the oxygen mask emergency/test knob. After releasing the knob; pressure quickly returned to 1960 psi. Test returned same result on FO (First Officer) side. Submitted ELB report and requested maintenance. When maintenance reported to the flight deck and I demonstrated a failed test; they said that it was ok because the pressure was returning to normal after the test. I explained our test parameters and requested that they check that the oxygen cylinder valve was fully open. Maintenance found the cylinder valve only partially opened. Once fully opened the valve and the system then checked normallyWith the valve in the partially open position insufficient oxygen was available for breathing through the mask. The aircraft was released from maintenance in this condition; where mechanics preformed ETOPS checks and issued a [Maintenance Release]. There were at least 3 opportunities to discover this problem before the airplane flew; and an additional opportunity before I discovered the problem.
Data retrieved from NASA's ASRS site 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.