Narrative:

During preflight I noticed that my oxygen mask was testing questionably. We notified maintenance control who dispatched a team to the aircraft. Upon arrival they verified that the O2 mask was not functioning properly. They worked with it for a while and where able to resolve the incorrect test. They noticed some damage on the O2 line to mask sleeve and decided to do a swap. Maintenance matched the part number of the mask in the pilot seat showing P/north: MC10-02-07 to the observer seat P/north: MC10-02-07. They called maintenance control to verify that it was okay to 'swap' these parts. At this point I mentioned that I did not believe that the parts where interchangeable but since the part numbers matched and maintenance control was aware; I resolved to the fact that I may be incorrect. Maintenance control began looking into the legality of a swap from the observer seat to the pilot seat. They noticed that the manuals had different part numbers for the pilot seats vs. The observer seats and began to question the installed equipment in the airplane. It was at this point the we realized that the aircraft's oxygen equipment was incorrectly installed. An observer seat mask was placed in the first officer's pilot mask slot. The key difference between the two is the lack of smoke goggle vents in the observer mask. Pilots mask: MC10-02-106 observer mask: MC10-02-07 maintenance notified and the aircraft was grounded until repairs were made. Perhaps we should require the crews to fully remove and test the oxygen masks during the first flight of the day. This would allow us to verify not only that the O2 masks/goggles are functioning; but they are serviceable and correct. Or preferably require that test on the daily checks.

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Original NASA ASRS Text

Title: EMB145 First Officer reports questionable test of his oxygen mask during preflight. When maintenance is called it is discovered that the part number is not correct and that an observer oxygen mask is installed at the First Officer's seat position.

Narrative: During preflight I noticed that my oxygen mask was testing questionably. We notified Maintenance Control who dispatched a team to the aircraft. Upon arrival they verified that the O2 mask was not functioning properly. They worked with it for a while and where able to resolve the incorrect test. They noticed some damage on the O2 line to mask sleeve and decided to do a swap. Maintenance matched the part number of the mask in the pilot seat Showing P/N: MC10-02-07 to the observer seat P/N: MC10-02-07. They called Maintenance Control to verify that it was okay to 'swap' these parts. At this point I mentioned that I did not believe that the parts where interchangeable but since the part numbers matched and Maintenance Control was aware; I resolved to the fact that I may be incorrect. Maintenance Control began looking into the legality of a swap from the Observer seat to the pilot seat. They noticed that the manuals had different part numbers for the pilot seats vs. the observer seats and began to question the installed equipment in the airplane. It was at this point the we realized that the aircraft's oxygen equipment was incorrectly installed. An observer seat mask was placed in the First Officer's pilot mask slot. The key difference between the two is the lack of smoke goggle vents in the observer mask. Pilots Mask: MC10-02-106 Observer Mask: MC10-02-07 Maintenance notified and the aircraft was grounded until repairs were made. Perhaps we should require the crews to fully remove and test the oxygen masks during the first flight of the day. This would allow us to verify not only that the O2 masks/goggles are functioning; but they are serviceable and correct. Or preferably require that test on the Daily Checks.

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.