Good evening,

I'm on final installation of my 912is .

I've two rubber+foam 50lt reservoir, looking to connect it together with one small aneourisse and then feed the engine via AN 6 fitting and -6 tube. ( only one fuel selector on-off)

Due to limited space under the seat this small aneourisse is around 1.2lt   70x70 x 230 mm alluminium square tube with male fitting welded on it.

Due small volume i looking to return the fuel in one tank and not on aneourisse.

Both tanks are connected to aneourisse via 2 AN10 fitting with tube 14 mm inside diam, i think will be enought to feed the  aneourisse from tank ( also returned fuel)

one vent port are on top of the aneourisse and it's connected to tank vent line


This will work fine?


I cannot install bigger aneourisse







  • Re: fuel reservoir + small aneourisse

    by » one year ago

    Sounds OK...should work fine....

    My Aircraft as standard has only one tank so no surge tank and the fuel returns to the main (77L) tank . the large 14 mm ID fuel line should mean there is almost no restriction on fuel flow....

    My only comment is that at only 1.2 L the surge tank is probably not doing anything so why bother with it just 14 mm ID line and a Tee joint....I have two wing tanks each with only 8mm ID line gravity feeding to the main tank all through a Tee no restrictions no "header" or any other tank.

    I also only have one ON/OFF tap for three tanks...simple and Idiot proof.

  • Re: fuel reservoir + small aneourisse

    by » one year ago

    ??? aneourisse ???  Even Google is clueless.  
    Based on the description, I am Guessing "Header Tank".

    The problem with drawing from a common feed and returning to only one side is that the return side tank will overflow if the cross-feed between the two main tanks cannot keep up with the imbalance.  10AN hose might be enough, but careful testing is advised.
    The return flow approaches 2L per minute.

    It is highly recommended that you return the fuel back to the header tank from where it originated.
    at 2L/min, the fuel pumps are going to suck the Header dry in a few minutes unless the main fuel supply can keep up.
    Again, 10AN hose might be enough, but careful testing is advised.

    Your header tank must be vented back to one of the tanks, not just a vent line.
    This line will occasionally "Burp" some Fuel

    If returning to the header tank is not possible, returning to the fuel supply line with a Tee connector very close to the tank should also work.

    You asked, "Will this work fine?"
    It might, but it is hard to tell without knowing the exact details of your installation.

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

  • Re: fuel reservoir + small aneourisse

    by » one year ago


    Yes header tank is the corret name, friend of mine call it aneourisse and i used to call it same .

    My project is a low wing, all fiber ( blackshape prime type).

    Below the seat , only available place to install header/collector tank,  ther's control bar passing throught and has only 70 mm from floor.

    I could build the tank higher with half hole around the control bar ( the shape will be like an U).

    At 50% of fuel ( 25lt each tank) , this higher header tank will be not full of fuel and at this point I dont think is worthy.

    Also if I increase width , with low fuel and high pitch may be a lack of fuel on inlet line.


    Doing header tank 70 x 70mm will be always full and even in high pitch with very low fuel, but in that case i cannot retur fuel on it.


    Yes , both reservouir has fitting for fuel return and is 15 cm above  AN10 fuel feeding line

    Both tank has vent line returning in fuselage and connected together + header tank with T and routed on high position behind seat and then routed on floor and overboard




  • Re: fuel reservoir + small aneourisse

    by » one year ago

    It is important that you understand that Carburated engines and fuel-injected injected engines have vastly different fuel systems.
    In a Carb'd engine if the carbs do not require fuel for a moment, the fuel flow can be stopped completely and the fuel pump will be fine with that.
    These pumps will attempt to maintain a constant Fuel pressure by varying the fuel volume.

    In a fuel-injected engine, the fuel pumps normally operate at 45psi.
    They are positive displacement pump; meaning they pump fuel at a constant Volume by varying the pressure.
    They are theoretically capable of making 100s of psi before the pump motors stall.
    Your fuel pumps will operate at whatever pressure is needed to move 120L/hr
    The pumps have a safety pressure bypass of ~100 psi built into them to prevent stalling the pumps.

    The 912is fuel pressure regulator returns all unused fuel back to the fuel tank.
    This return fuel is NOT clear fuel.  It contains numerous small bubbles similar to what you see when you open a soda bottle.
    They are NOT "Air".  They are mostly Butane gas vapors, and will recondense and be absorbed back into the fuel if given a chance.
    You do NOT want to vent these vapors to the atmosphere.
    The return fuel flow should be returned to a fuel tank.
    It does Not need to return to the space above the fuel.
    It can be returned through the bottom or the side of the tanks without issue.
    Getting the return fuel back into the tank by any means is the goal.

    Because of the high circulating volume (120L/hr), it would be recommended to return the fuel to your header.
    The Header Tank vent should NOT be vented overboard without first passing through a main tank.

    As stated earlier, routing the return fuel to a main tank is a possibility as long as your two main tanks can freely cross-feed to share the returning fuel. 60L/hr will need to get to the opposite tank freely.
    Splitting the return fuel line to both tanks could possibly help with the imbalance if needed.

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

  • Re: fuel reservoir + small aneourisse

    by » one year ago

    Good Afternoon ,

    I'm still figuring out how to do, i notice on video of 912is header tank( with glass for test) how many buble create, at certain point 3/4 of header tank was turbulent with buble even if is very high compared to mine ( max 100 mm).

     So i tinking to skip the option of return on small header tank.( 1.5 lt) to awoid turbulent/ bubbled fuel feeded to engine.

    I will split and return on fuel tanks directly.

    Now i have another dubt, about fuel pump installation.

    Lowest point and nearest to tank feeding is in cabin below pilot seat.

    Many wire - nose gear elec motor - battery are present so i guess in case of fuel leakage wil be dangerous ? 


    Other option, install it on firewall but will be slanted due lack of space and will be a bit higher compared to cabin installation option 

    Any suggestion?

    Wire /tube are not on final position , not aeronautcal wire are temporary to test the sys, works still in progress ...









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