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Thread: fuel injected engine fuel return lines

  1. #11
    Administrator ZenithOwner.com's Avatar
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    Kevin, I believe you are correct-you can use a header tank, or plum the return lines back to the original tank the fuel is feeding from.
    Mark Pensenstadler
    Site Admin
    Price's Airpark, Linden, MI (9G2)
    S-10 | S-6S | RV-7 | Cherokee 160 | Zenith Cruzer

  2. #12
    Kevin, in addition to Mark's response: Header tanks are mainly used in fuel infected engines, even though some vintage, carbureted aircraft also had header tanks. The main advantage of a header tank is, that even if air gets in the fuel line in the wing tanks, the air would not make it to the engine (unless the header tank is empty). It also allows to completely empty the wings tanks, while the header tanks is still available as a reserve. Depending on the engine, this is either a nice to have (ULPower) or, in case of a directly injected engine (Viking) mandatory.

    Engines, like the ULPower or the AeroMomentum with a port or throttle body fuel injection continuously circulate high amounts of fuel back to the tanks. Some air in the fuel line would therefore typically at maximum cause a hiccup and a scare, as most of the air will simply be returned to the tank.
    Direct injected engines like the Viking have a different layout, to my knowledge (take this with a grain of salt) with no continuous fuel circulation. Once the air is in the fuel line to the engine, it has to go through the injectors, what leads in case of a larger air bubble to an engine failure. A header tanks is for such engines therefore mandatory.

    Now, one might think that a header tank is always the 'better safe than sorry' choice. As often, things are sadly not that simple: A header tank adds quite a bit of complexity to the fuel system: Air which makes it into the header tanks somehow needs to be drained, you probably want shut-off valves between the wing tanks and the header tank, which are easy to forget to turn on, an additional fuel gauge might be a good idea, it needs to be installed somewhere and so on...

    By far the most engine failures in experimental aircraft are caused by issues with the fuel system. Unless a header tank is required by the engine manufacturer, I do not think that the relatively small benefits it provides, justifies the significantly increased complexity of the fuel system.
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  3. #13
    Thanks Mark and Oliver for your replies, good info. As an aside, I enjoy following both your builds, thanks for putting them up for the rest of us.

    Kevin

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