Fuel System

1st Official Post

    It's my understanding that the fuel system will be rewritten at some point in the future. I decided to have a look at the current system and fix the fuel used reset bug on the A350, I got it working using the tmd logic below

    // A350 FUEL TEST - reset fuel used when parked
    <[logic_invert][RPOnGround][]
    <[string8][Input][InAir.Output]>
    >

    <[logic_and][RPFuelUsedResetCondition][]
    <[string8][Inputs][ RPOnGround.Output NoEnginesRunning.Output ]>
    >

    <[event_edge_rising][RPFuelUsedResetTrigger][]
    <[string8][Input][RPFuelUsedResetCondition.Output]>
    <[string8][Events][ Engine1FuelUsed.Reset Engine2FuelUsed.Reset APUFuelUsed.Reset ]>
    >

    While I was having a look around, I was wondering if the gross weight and fuel load are accessible? I was able to get the FOB to decrease based on fuel used, but actual fuel mass and gross weight don't seem to be modifiable. I also had a look at the C172, but it seems quite simplified

    Below is a sped-up video showing FOB depletion. Is it possible to make the Gross weight dynamically change? Am assuming its a no go area for modders.


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    I have functionally recreated the FUEL SYSTEM in the C130H according to the principle of the C172 - it works according to the model with 8 internal and 2 external tanks, 4 engines, dump system, various pumps and RefuelPods. I am happy to make my experience available.

    Tschüss, Michael (🍎🚁)

    Configurations:

    - MacBook Pro (16", 2024); Chip: Apple M4 Max; actual macOS
    - Controllers: | WinWing: URSA MINOR-Fighter-Joystick R, EFIS-L & FCU & EFIS-R | Thrustmaster TCA AIRBUS EDITION: 2x Quadrant, 2x Quadrant Add-On | Pro-Flight-Trainer: PUMA X | Steelseries: Nimbus+

    - iPad (12,9", 4th Generation, RAM: 6 GB); actual iOS | Steelseries: Nimbus+

    Thanks, I managed to get it working 🙂 GW and GWCG are adjusting automatically. just need to hook up the right and center tank.


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    Maybe my approach to the C130 will give you suggestions.

    This is the fuel system, which is completely functionally simulated:


    I have divided this into the C130 (only the relevant headings for the fuel flow from the tank to the engines are shown):

    • fuel system
      • fuel system - quantity
        • fuel system - quantity - data
        • fuel system - quantity - on bord
        • fuel system - quantity - trend
      • fuel system - elements
        • fuel system - elements - tanks
          • fuel system - elements - tanks - centers of gravity
          • fuel system - elements - tanks - tank 1
          • ...
      • fuel system - fuel flow
        • ...
        • fuel system - fuel flow - boost
          • ...
          • fuel system - fuel flow - boost - tanks
            • fuel system - fuel flow - boost - tanks - tank1
            • ...
          • fuel system - fuel flow - boost - bypasses
          • fuel system - fuel flow - boost - crossfeeds
          • ...
        • fuel system - fuel flow - engines
          • fuel system - fuel flow - engines - engine 1
          • ...

    The attached file contains the complete segment FUEL, which I also developed in a separate subfolder and then moved to the c130.tmd.

    Files

    c130_fuel.tmd.txt 249.61 kB – 34 Downloads

    Tschüss, Michael (🍎🚁)

    Configurations:

    - MacBook Pro (16", 2024); Chip: Apple M4 Max; actual macOS
    - Controllers: | WinWing: URSA MINOR-Fighter-Joystick R, EFIS-L & FCU & EFIS-R | Thrustmaster TCA AIRBUS EDITION: 2x Quadrant, 2x Quadrant Add-On | Pro-Flight-Trainer: PUMA X | Steelseries: Nimbus+

    - iPad (12,9", 4th Generation, RAM: 6 GB); actual iOS | Steelseries: Nimbus+

    Excellent, that C130 is an amazing piece of work. I am hoping to add fuel dumping once I've tweaked everything with the A350 (still need to add center pump draining before wing tanks)

    I am trying to figure out Engine1FuelMeteringUnit.Output, do you know if this uses kg/s kg/h pounds?

    As Michael has pointed out, take a look at the real aircraft systems, be it fuel, electrics, hydraulics or even the toilet system (which is a suction system) and build it all as per the real aircraft. FS4 is great in that respect as it does give you the chance to do it. To a former simpit builder this sim would be a gold mine, but sadly that's where it also fails as it doesn't support such ideas.

    Steve

    Hi Steve, yes, I have successfully rebuilt the fuel system using real-world logic. Just adding the finishing touches, then will test flight tonight. So far, I am just running the aircraft on the ground, and adjusting fuel flow. I am familiar with electric, pneumatic, etc. I never bothered to look at the fuel because I thought it was incomplete. This sim is a modder's dream

    I have a simpit at home, am using the Dll to output a few things, but for my bass transducer, I pretty much have all I need. I want to output turbulence to the transducer in my cockpit seat, but I don't think that's possible .

    Center logic is 85% complete. I need to tie it into the flap position - After that, I'll add fuel leaks, refueling, and link up the Jettison switches.

    Quote from 777Driver

    ... I am trying to figure out Engine1FuelMeteringUnit.Output, do you know if this uses kg/s kg/h pounds?

    In FS 4, these units are used:

    Code
    //  fuel system - informations - fs 4
//----------------------------------------------------------------------

//  units

//  - PRESSURE:                 Pa  (QNH 101325 Pa = 1013.25 hPa = 1.01325 bar = 14.69595 PSI)
//  - FUEL TEMPERATURE:         K
//  - FUEL QUANTITY:            kg
//  - FUEL FLOW:                kg/s

    And these data apply to the tanks:

    Code
    //  - TANK STATION R0:          SIDE WALL - CENTER
//  - TANK STATION DIMENSIONS:  SIDE WALL - LENGTH (X) HEIGHT (Y)
//  - TANK MASS:                kg (DEFAULT)
//  - TANK CAPACITY:            m3

    Tschüss, Michael (🍎🚁)

    Configurations:

    - MacBook Pro (16", 2024); Chip: Apple M4 Max; actual macOS
    - Controllers: | WinWing: URSA MINOR-Fighter-Joystick R, EFIS-L & FCU & EFIS-R | Thrustmaster TCA AIRBUS EDITION: 2x Quadrant, 2x Quadrant Add-On | Pro-Flight-Trainer: PUMA X | Steelseries: Nimbus+

    - iPad (12,9", 4th Generation, RAM: 6 GB); actual iOS | Steelseries: Nimbus+

    Quote from 777Driver

    ApfelFlieger have you added refueling? I'm thinking of going down another rabbit hole, using an external lightwight mod that can add a refueler, the user selects the amount of fuel to load, and it gets pumped into the relevant tanks at a realistic rate.

    Yes, I did. However, you still reach the logic limits in FS 4. I'll try to show it in a few words:


    A. Sketched, the fuel flow in the FS 4 proceeds as follows:


    A.1. ENGINE

    (1) [fuel_tank]
    - defined fuel quantity available.

    (2) [fuel_valve]
    - is opened/closed and determines maximum fuel flow

    (3) [fuel_rail]
    - connects (2) and (4) and defines [DesignFlow] and [Pressure]

    (4) [fuel_pump]
    - - is OFF/ON and determines maximum fuel flow

    (5) [fuel_rail]
    - connects (4) and (6) and defines [DesignFlow] and [Pressure]

    (6) [fuel_engine][Engine1FuelControl][]
    - burns the fuel with the data for [InputPressure], [AddFlow] and [InputFuelFlow]


    A.2 DUMPING:

    (1) - (5)

    (6) [fuel_engine][FuelDumpMastRightDumping][]


    A.3 - REFUELING AS TANKER IN THE AIR:

    (1) - (5)

    (6) [fuel_engine][RefuelPodRightBasketOutlet][]


    B. Refueling your own aircraft on the ground and in the air:

    Here the order is reversed from (6) to (1).

    But how do I invert (6)? I'll try it out later to see if it works with a negative [InputFuelFlow], because I didn't test that. And I also need that with the C130, if it goes to a tanker itself.

    For the floor refuelling, I have already successfully tested the refuelling from a floor tank, but not activated it. However, the external SINGLE-POINT REFUEL CONTROL PANEL is functionally simulated with the C130.

    Tschüss, Michael (🍎🚁)

    Configurations:

    - MacBook Pro (16", 2024); Chip: Apple M4 Max; actual macOS
    - Controllers: | WinWing: URSA MINOR-Fighter-Joystick R, EFIS-L & FCU & EFIS-R | Thrustmaster TCA AIRBUS EDITION: 2x Quadrant, 2x Quadrant Add-On | Pro-Flight-Trainer: PUMA X | Steelseries: Nimbus+

    - iPad (12,9", 4th Generation, RAM: 6 GB); actual iOS | Steelseries: Nimbus+

    Quote from ApfelFlieger

    ... But how do I invert (6)? I'll try it out later to see if it works with a negative [InputFuelFlow], because I didn't test that.

    It actually works - I could have come up with it much earlier.💪🤣


    With DEFUELING ON GROUND it ends in the C130 like this:


    With REFUELING ON GROUND it starts in the C130 like this:

    Tschüss, Michael (🍎🚁)

    Configurations:

    - MacBook Pro (16", 2024); Chip: Apple M4 Max; actual macOS
    - Controllers: | WinWing: URSA MINOR-Fighter-Joystick R, EFIS-L & FCU & EFIS-R | Thrustmaster TCA AIRBUS EDITION: 2x Quadrant, 2x Quadrant Add-On | Pro-Flight-Trainer: PUMA X | Steelseries: Nimbus+

    - iPad (12,9", 4th Generation, RAM: 6 GB); actual iOS | Steelseries: Nimbus+

    Christmas has come early for me 😁 Thanks again, guys. The fuel system is fully functional. The A350 has a refuel button on the overhead. I wired that into the refuel simulation, . All that's left is to implement the correct logic (wings then center). As a test, I've only hooked up the center.

    On ground logic for refueling, Fuel Jettison, crossbleed, and leaks next. It looks like the devs already included the ECAM messages

    I would have been happy with just the fuel burn; this is excellent. I couldn't ask for better tutors 🙏

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    Block fuel entry in FMS can be used to select the requested refuel amount. The refuel rate is around 2000kg per min

    Fuel Jettison rate is 1600kg per minute.

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    A question for the devs, or anyone who has designed the fuel tanks - Everything's working fine now, but I was up for hours last night reading through forum posts trying to figure out how the fuel tank geometry works. The last thing I needed to add was engine flameout when each wing tank gets below 100kg, but for some reason, the tanks would stop draining at 500kg. It turned out that adjusting the tank fixed the issue.

    What exactly is the last line? -1.50? // ROB FUEL TEST - left wing tank outlet
    <[tmvector3d][Outlet0][ 1.63831 5.817829 -1.50 ]>

    The last bit of fuel drains when I changed that from -1.25 to -1.50 Do you guys use some software to visibly see the tank? Is -1.50 to the height of the pumps that drain the fuel?

    • Official Post
    Quote from 777Driver

    A question for the devs, or anyone who has designed the fuel tanks - Everything's working fine now, but I was up for hours last night reading through forum posts trying to figure out how the fuel tank geometry works. The last thing I needed to add was engine flameout when each wing tank gets below 100kg, but for some reason, the tanks would stop draining at 500kg. It turned out that adjusting the tank fixed the issue.

    What exactly is the last line? -1.50? // ROB FUEL TEST - left wing tank outlet
    <[tmvector3d][Outlet0][ 1.63831 5.817829 -1.50 ]>

    The last bit of fuel drains when I changed that from -1.25 to -1.50 Do you guys use some software to visibly see the tank? Is -1.50 to the height of the pumps that drain the fuel?

    The outlet0 position is a 3d vector in the aircraft coordinate system. The last component is the vertical component. Lower values means the outlet sits lower and it might be possible to drain more fuel with that geometry.