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Fuel starvation after electrical failure?

in 912 / 914 Technical Questions 6 years ago

  • Re: Fuel starvation after electrical failure?

    by » 6 years ago

    Here's a link to the best discussion I have seen regarding 914 fuel pumps configuration:

    http://contrails.free.fr/engine_pierburg_en.php


    Hello Ken,

    Thank you, much appreciated. Seems that different set ups find their approval from manufactures and that the builder is "free" to choose.
    Anyways, I have the "a la Rotax" way (done by the original builder). My main concern was the electrical failure way of handeling. Still I find it a bit odd, that I can't find any warnings in my POH or the Rotax manual about the dependency on electricity. In case of an alternator failure there is the need of "to land asap", before the battery is dead.
    I have flown Robin aircraft with Centurion Diesel engine's, which were dependent on FADEC. In the POH as well on the checklist it was emphasized that in case of an electrical failure you airtime would be limited to remaining battery life before systems would die.
    I have a lot of confidence in the Rotax and it's systems, for me personally it's about being aware of how the systems work and what the procedures are when something happens. I prefer to rehearse the steps safely on the ground so I can act automatically when I'm up and focused.

    Kind Regards, Renz
      
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  • Re: Fuel starvation after electrical failure?

    by » 6 years ago

    The standard Rotax 912 has a mechanical engine-driven fuel pump, and an optional electric auxiliary pump. This is different from the 914. I don't know why the 914 couldn't also use a mechanical pump.
      
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  • Re: Fuel starvation after electrical failure?

    by » 6 years ago

    ... I don't know why the 914 couldn't also use a mechanical pump.


    A normally aspirated engine always has a vacuum of some level in the carbs so any fuel pressure will do.

    The fuel pressure needs to be more than the Boost pressure of the turbo to get fuel into the carbs.
    The Boost pressure can exceed 5psi.
    Normal Mechanical pumps typically deliver 2-5 psi. (Low Pressure)
    The electric pumps used in the 914 can deliver fuel at ~15psi. (Medium Pressure).

    It would be possible to design a medium pressure mechanical pump
    but the electric pumps are off the shelf items from the turbo automotive world.
    It is a matter of economics.
    Multi-Millions of turbo auto engines vs. a few thousand 914's at most.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
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