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Fuel return line

in 912 / 914 Technical Questions 13 years ago

  • Re: Fuel return line

    by » 13 years ago

    Hi Ivor,

    Now that I have a little more facts I do indeed believe it may be vapor in the fuel line. I have seen many aircraft that have flown and land. Then 15-30 minutes later start an engine and have low pressure for a while. Some engines never miss a beat and the fuel pressure comes up eventually from the cooler fuel running through the system, but some have experienced and engine cough. This should be rectified. You may want to make sure all lines are in a heavy fire sleeve material and relocate a fuel line if it is in a particularly hot area. I usually see this with tighter cowed engines and no venting on top for the heat to escape after landing so the temps build and with no air flow or fuel flow the lines heat and vapor forms. Not everyone has this problem, but it does happen. Find a way to relieve the heat, insulate and or move the fuel lines.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Fuel return line

    by » 13 years ago

    Hi Rodger, and thank you.
    I will re-locate fuel lines where necessary, I think particularly from the electric pump to the mechanical pump. What about covering the mechanical pump in an asbestos or similar shield, I think it gets very hot because of the location on the gearbox.

    Regards
      
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  • Re: Fuel return line

    by » 13 years ago

    Hi,
    ....and what about "short" and "slim" return lines? I mean: my Tecnam P92 has a short return line (a very small diameter tube, see photo) that goes in between the gascolator and the fuel pump, some 15 cms before this last one. Is it that acceptable? I never experienced loss of pressure or vapor lock.
    Recently, I have mounted a new fuel pump (the new kind, gray in color) and my fuel pressure gauge reading is increased to 5-6 psi (the fuel pressure gauge is mounted between the pump and the "T" of the return line). Having flown about 3 hrs after the change, the system seems to work well.
    Thanks and Ciao a tutti!
    [attachment]C:\fakepath\IMG_1082.jpg[/attachment]
      
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  • Re: Fuel return line

    by » 13 years ago

    Hi,
    ....and what about "short" and "slim" return lines? I mean: my Tecnam P92 has a short return line (a very small diameter tube, see photo) that goes in between the gascolator and the fuel pump, some 15 cms before this last one. Is it that acceptable? I never experienced loss of pressure or vapor lock.
    Recently, I have mounted a new fuel pump (the new kind, gray in color) and my fuel pressure gauge reading is increased to 5-6 psi (the fuel pressure gauge is mounted between the pump and the "T" of the return line). Having flown about 3 hrs after the change, the system seems to work well.
    Thanks and Ciao a tutti!
    IMG_1082.jpg (You do not have access to download this file.)
      
    Report

  • Re: Fuel return line

    by » 10 years ago

    Hi
    I have until now only had a simple fuel system, but have now ordered parts so that i can install one extra electrical fuel pump and a fuel pressure gauge. And also a fuel return line.

    I would like to check with others on this forum if i am installing the fuel return line correct. I can not take it to either the fuel tank or the gascolator (the gasculator has no fuel hose nippel)

    Here is how i plan to install the mechanical fuel pressure sender and the fuel return line:

    The simple system i have now consists of a fuel hose from the mechanical fuel pump to a T-piece which sends the fuel to both carbs.

    I AM PLANNING TO INSTALL LIKE FOLLOWING:

    1. To the fuel hose between the mechanical fuel pump and the T-piece i will install the new T-piece with restrictor for the fuel pressure sender from which i attach the hose to the pressure gauge in the cockpit.

    2. For the return line i will install a T-piece with restrictor on the same fuel hose directly after the T-piece with the fuel pressure sender.

    3. The return line will then be drawn and installed to the fuel hose incoming to the gascolator with a similar T-piece with restrictor. (instead of directly to the tank or the gasculator).

    4. Is it right thought by me to use a T-piece with restrictor on both ends of the return line when i install it to the fuel hoses?
      
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