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Return Fuel Line Quantity

in General Tech Discussion 6 years ago
Can any of the ULS operators shed some light what might be the approximate unused fuel under a normal one (1) hour flight...departure, cruise (5K rpm) and descent that returns to my header tank?

Thank you,

Bill

  • Re: Return Fuel Line Quantity

    by » 6 years ago

    There are a bunch of variables that are involved here.
    Fuel pressure, Orifice Size, Temperature, Etc. that make it difficult to give an accurate answer.
    But 3-5 gallons per hour would be a reasonable ballpark number.

    The fuel pressure is regulated at 3-5psi so the engine RPM is immaterial.
    If you have an electric AUX Fuel Pump, you will be returning fuel even with the engine OFF.

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

    Thank you said by: Bill Russini
      
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  • Re: Return Fuel Line Quantity

    by » 6 years ago

    Thank you Bill, those figures would confirm what I am experiencing right now. I only have a supply line transducer and the indicated fuel burn w/o a return line transducer are close to 50% greater. For example, my actual burn on my last two flights was 4-5 The fuel flow burn indicated 8 gallons +/- on both flights. I think it’s time to install the recommended return line transducer to get a more accurate burn. Thanks again
      
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  • Re: Return Fuel Line Quantity

    by » 6 years ago

    FYI, after collecting a considerable amount of fuel burn data, ‘K’ factor corrections for the most part useless w/o the return line transducer
      
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  • Re: Return Fuel Line Quantity

    by » 6 years ago

    Its interesting you find K factor corrections useless. I have just a supply line transducer on my 912uls (no electric aux pump) and once I got my K factor calibrated for my normal cruise conditions it has been quite accurate and very usable for over 600 hours now.
      
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  • Re: Return Fuel Line Quantity

    by » 6 years ago

    Fortunately I/we only fly at most 2 hour segments and stick the tanks b4/after. My original float gauges are accurate fm 1-3 gallons.

    I’m happy to read ur ‘K’ adjustment(s) worked...thanks for ‘jumping in on the forum’.

    Btw, tech support fm Flight Data have been wonderful in their support.
    Thank you said by: Rob Seaton
      
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