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Sherv avatar image
Sherv asked donstim commented

Fuel.system section in flight_model.config

Hi MSFS Team. I am trying to implement a fuel cutoff switch similar to what is in the 747. I realized trying to use the xml fuel template switch ( ASOBO_FUEL_Switch_Valve_Template )does not work since I do not have a fuel.system section in the flight model. If I try and and this section , aircraft editor either locks or crashes. Is there any plan to update the editor to include this section? Was this section for the 747 manually created?


Thanks,

Shervin

aircraftflightmodel
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Doing some more research it looks like the FUELSYSTEM_VALVE_SWITCH variable is contained in a WASM module? Does that mean I have to create a WASM module for the fuel system?

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FlyingRaccoon avatar image
FlyingRaccoon answered FlyingRaccoon commented

Hello Shervin,

The section should be named FUEL_SYSTEM as documented here: https://docs.flightsimulator.com/html/Content_Configuration/SimObjects/Aircraft_SimO/Flight_Model_Definition.htm?rhhlterm=fuel_system#[fuel_system]

This section is not editable through the AircraftEditor at the moment (it will in the future) but it shouldn't crash though. Make sure its content matches what's specified in the doc.
I can investigate on the cause of the crash if you provide me with your package.

Regards,
Sylvain

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But that documentation simply consists of a bunch of parameter names. There are no descriptions of the parameters included nor discussion anywhere I could find of how they are used (e.g., what are allowable triggers?) and interfaced with other systems.


Also, are you aware of the bug in the default A320 fuel system that causes fuel to disappear if you start cold and dark (no engines or APU running and satisfy the trigger for the external fuel transfer valves to open, the fuel transfers out of the outer tanks, but does not transfer into the inner tanks. It simply disappears.
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We know this is not ideal. This section will be documented as precisely as the electric systems were documented a few weeks ago. In the meantime, this is the best we can provide.

I am personally not aware of the A320 issue but devs might be. Have you created a zendesk ticket?
If you can provide me with repro steps (in a dedicated question) I can reproduce the problem and make sure it has been forwarded to the devs.

Regards,
Sylvain

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Thanks Sylvain. I did take a look at that section. I'll have to tinker around with it some more. I think I may have to draw out the fuel system first then try and translate into the proper syntax. Would be nice if in the future implementation in Aircraft Editor , there is some sort of a visual reference to help debug/analyze the fuel system.


Thanks!

Shervin

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donstim avatar image
donstim answered donstim commented

"Not ideal" is a bit of an understatement, but okay, I'm confident it will get there. Thanks.

As for the A320 issue, I shouldn't have limited it to the A320. It is a fuel system issue, so it would affect any airplane that uses this new fuel system and has fuel transferred from one tank to another based on a triggering value. I did not create a Zendesk ticket as I had provided this info to our rep on the Asobo forums to give you all directly. Maybe that did not take place. I can create a Zendesk issue if it would help. There are actually 2 issues I've found with the new fuel system that would affect any airplane using the new fuel system.

The one I described - Start Asobo A320 cold and dark anywhere. Turn batteries and external power on. Adjust fuel quantity as follows: no fuel in the center tank, full left outer and inner tanks, less than 250 gallons (e.g., 216 gallons) in each inner tank. Watch the outer tank fuel levels drop without the inner tank levels (where the fuel should be going) changing. Fuel is simply disappearing.

Second issue: Any amount entered as unusable fuel is effectively being added to the total tank capacity rather than being subtracted from it. Fuel continues to be emptied from the tank to a negative amount of fuel equal to the unusable fuel. For example, for a tank with a total capacity of 2 gallons, with 1 gallon being unusable, the engines would not quit until 2 gallons of fuel is burned leaving a fuel quantity of -1 gallons. Is this why the unusable fuel quantity was set to zero for the default airplanes using the new fuel system?

To reproduce this issue, you will need to change the unusable fuel quantity for any given fuel tank from zero to some positive value in any airplane using the new fuel system. Put a small amount of fuel in that fuel tank, start the engines and burn all the fuel in that tank. The engine will not quit due to fuel starvation until the amount of fuel originally put into the tank plus the unusable fuel (rather than minus the unusable fuel) is burned.

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This is a perfect example of why we need a visual debugger in the Aircraft Editor. Maybe there is a some fuel line that leads to nowhere? There are so many lines in the fuel system for the A320 and 747 it's hard to tell.... at least for me.

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Both these issues are fixed and will be available with the Performance Plus update.

Looks like your bug report on the forums was considered :)

Regards,
Sylvain

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donstim avatar image donstim FlyingRaccoon ♦♦ ·
Thanks! And here I thought this forum was just for discussing the SDK!
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It is. As the bug you described potentially affected all third party products, I consider it SDK related.
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donstim avatar image donstim FlyingRaccoon ♦♦ ·
Well, I'm afraid it doesn't appear to have been completely fixed. For example, with the A320, the APU will burn fuel from the center tank, and if there is no fuel in the center tank, it will take it from the left main tank. This can be verified by putting fuel in both tanks and observing that center tank fuel is used, then just fueling the left main tank and observing that left main tank fuel is used. When the left main tank gets to the unusable fuel quantity, the APU will shut down due to fuel starvation. This is all well and good.


The issue is if the APU is burning from the center tank, and then the center tank gets to it's unusable fuel quantity (or only the unusable amount is loaded initially), the APU will quite happily run forever without burning any fuel at all. If there is initially only the unusable fuel quantity loaded in the center tank, then the left main tank must have more than its unusable fuel quantity for the APU to start, but once started, it will run along without burning any fuel. Note: for this testing no fuel was loaded in any of the other tanks. (And this testing was conducted using the FBWA320, though I would expect the same results from the default A320.)

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Hi donstim

I forwarded the issue to the developer in charge of the fuel system.
Thank you for reporting this.

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What do you mean with this new fuel system? Is there some configuration to switch between some legacy and a new fuel system?

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In the SDK for the flight_model.cfg file there is a [FUEL] section and a [FUEL SYSTEM] section. Both can be used to configure the fuel tanks with the latter section allowing much more flexibility in terms of specifying the fuel lines, valves, pumps, junctions, and triggers for certain actions. If you use the [FUEL SYSTEM] section for specifying the fuel tanks, it will override the fuel tank information in the [FUEL] section. (You will still need to specify items like fuel type that are not in the [FUEL SYSTEM] section.)


There is a SimVar you can check that will identify if your airplane is using the new [FUEL SYSTEM] section.

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donstim avatar image
donstim answered donstim edited

Thank you for the response Sylvain, but that particular altimeter issue is not what I am referring to. I am referring to an inaccurate standard pressure vs altitude relationship being used and incorrect implementation of the effect of temperature on altimeter altitude vs height above ground. The current preview build, which attempts to fix these issues with the production version, has made what used to be a fairly benign couple of issues into very serious bugs. The current status will make it very difficult for anyone to fly on VATSIM or any other online network.

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My bad, about this issue, we are aware the situation is still incorrect in preview.

We have a potential fix but we want to test it further as we're worried of possible side effects.
I'm afraid we won't be able to fix this in the Performance Plus release.

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donstim answered donstim edited
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