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Q211212 - On flight crew oxygen masks

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  • Q211212 - On flight crew oxygen masks

    Hi Folks,

    The question refers to the settings of the flight crew oxygen masks. While two of the answers are clearly wrong, two seem nearly right to me:

    In Emergency mode the mask will supply oxygen at slightly above normal pressure for use above 32,000 ft.
    In Normal mode the mask will mix oxygen with cabin air as a diluter demand system.

    I went for the first option because it seemed wholey right. The second option was 'spoiled' by being called 'DILUTER' and I didn't think it was labelled that way.

    Otherwise what have I got confused?

  • #2

    We don't always like, or agree with, the wording of the examiner - as in this case! It is quite a weak question because, as you point out, several answers are 'almost' right. Diluter demand is a valid name for the 'normal' position, and is used several times by the examiner. We have good feedback on this question, so we are confident with the wording used. Therefore we have a duty to our customers to show the questions as they will be encountered in the exams. Hope that helps?


    • #3
      Fair enough - I'll have to remember that Diluter is a word. But even so, why is this answer more right than the emergency one? Or is this just something to learn and move on?


      • #4
        Okay, here is a complete explanation of each answer. Perhaps you might want to re-visit the lesson to confirm each point in turn.

        In the position DILUTE oxygen is mixed with air from outside the mask - completely correct.

        When switched to the position 100%, oxygen is always supplied with some overpressure - incorrect. It is 100% oxygen, but not overpressure.

        Below a certain altitude the oxygen mask switches automatically to constant flow - incorrect. As altitude changes the mix of oxygen and ambient changes, but not to constant flow - it is still a 'demand' system.

        When selected to the position EMERGENCY oxygen is supplied with some overpressure above a certain altitude - incorrect. In position EMERGENCY it will supply 100% oxygen with overpressure at any altitude.


        • #5
          Keep them coming though Martin - good to see you questioning, as it shows you want to really understand all of this stuff. Your questions may well help someone else to have a 'light bulb moment'!


          • #6
            Brilliant thank you. I get it now. I didn't read the certain altitude bit as you have written it. I need to remember to read it more literally. Yes - if we had been talking about it I would have known it did it at any altitude. Just read the answer differently.