Originally Posted by
kiwibrit
It's decades since worked with an airliner - VC10 in the RAF. But IIRC a functional check of all the passenger oxygen masks was an item of a periodic maintenance schedule. I assume that I still so with modern airliners? In which case, I would expect the airlines to be concerned at a high incidence of failure (25%) and to raise the issue with Boeing and the CAA / FAA. So it would not have needed a whistleblower to raise concern effectively. I can't see that the story adds up. That said, I accept that I am a long time away from the aircraft maintenance scene.
No system based on single use chemical oxygen generators or pyrotechnic valves will undergo a 'functional check', meaning an actual check of delivering oxygen in an emergency situation. By functional check they mean the mask is still in one piece, not dried out, the bulkhead hinge opens, and the hoses haven't fallen off. This does not constitute a 'functional check', if so, every test would require a full replacement of the whole SINGLE USE emergency oxygen system, certainly a multi million dollar cost item. That is the reason they are NEVER tested. Also, how often do airlines suffer depressurization with extended high altitude flight, where some failed masks would result in detectable injury to passengers? Luckily very rarely, as most incidents result in immediate expeditious descent to breathable atmosphere, where in such an event a lack of functioning mask would almost be undetectable and its use practically unnecessary, but there are regimes of flight where an emergency descent would be impossible for extended periods, like most of the Chinese highlands. And you're still surprised Boeing would under-report a major safety issue, after MCAS, 777X doors, pickle forks, trim wheel etc etc. ad nauseum? Really get ahold of yourself.