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CodenameJack447 avatar image
CodenameJack447 asked FlyingRaccoon answered

FuelSystem: Problems with Junctions in Su9

Dear Asobo developers.

As much as I try to understand what you have done with the Fuel system from SU8 to SU9, it is clear that something is wrong with the junctions since then.

I don't know what you understand by junctions, but what I understand by junctions is the union of two or several lines, which, if open, should allow the flow of fuel to pass without offering any resistance, at least it worked like this until now. The most obvious problem is that if I have two junctions joined by a line, I don't care which direction the fuel goes, there is a clear resistance to the passage of it that there wasn't before. I haven't put options on these joints because it was not necessary, the fuel passed freely according to the pressure of the tank pumps or if the valves were open or closed, but now it is something impossible.

A example will be:

- Tank1

- Tank2

- Tank1Pump

- Tank2Pump

- JuncA

- JuncB

- JuncC

- JuncD

- Valve1

- Valve2

- Valve3

- Valve4

- Valve5

- Valve6

- Valve7

- Tank1 to Tank1Pump

- Tank1Pump To JuncA

- JuncA to Valve1

- Valve1 to Tank1

- JuncA to JuncB

- JuncB to JuncC

- JuncC to Valve2

- Valve2 to Tank2

- Tank2 to Tank2Pump

- Tank2Pump to JuncD

- JuncD to JuncC

- JuncD to Valve7

- JuncB to Valve3

- JuncB to Valve4

- JuncC to Valve5

- JuncC to Valve6

Assuming I want to get fuel from tank2 to tank1, I simply close tankpump1 and all valves except valve1, and fuel flows from tank2 through the tankpump2 and through the junctions. And vice versa, when it comes from tank1 to tank2, pump2 closed, valve2 open and the rest of valves closed. When this worked great in SU8, in SU9 it is unfeasible, since Fuel rate is reduced as it passes through each junction. Each junction opposes a resistance that did not exist before, and fuel is not escaping everywhere since the rest of the valves are closed as I said. Using these parameters #FuelFlowAt1PSI:0.1#Volume:0.24, which are the default values and the pumps go to 45 psi, which should be enough to move fuel is not working in SU9, while in SU8 worked reall great. If there are no junctions, there is no problem. But it is not a solution since those junctions are necessary to move fuel to other tanks or even engines through check valves open or closed.

in some of these lines I am being forced to add parameters like #FuelFlowAt1PSI:20#Volume:0.24 (changing volume has no effect), but it is impossible to make the fuel flow equally in both directions at the same rate.

It is evident that you have changed something and that you have not documented, or you are not aware of what you have done and you have a bug. But I hope you solve it or give us some information.

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Hello @CodenameJack447

Just to make sure I understand.
You diagnosed this issue by watching the FUELSYSTEM_LINE_FUEL_PRESSURE simvars in SU9 and seeing a difference between the configuration with and without junctions, am I right?

If the junctions are behaving this way, this is definitely not on purpose and I'll investigate.
If you can provide me with the FUELSYSTEM section you made your tests with to make sure we're in the same conditions, that would be helpful.


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CodenameJack447 avatar image
CodenameJack447 answered

Hi, yes is Concorde related, so the best example is you check it if you have access as I suppose you have access to it because it is in the marketplace. In SU8 the fuel transfer worked correctly, in SU9 it stopped working in two aspects, transfer of tanks 9, 10 and 11 between them, as well as directly to the engines since there are many junctions along the way. Also, I am designing the fuel system of the f-15, and although it is smaller I am facing the same issues when the fuel has to go through joints.

I think the best thing to do is to check it out for yourselves. since you have a plane in which you can manipulate switches.

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CodenameJack447 avatar image
CodenameJack447 answered masterrob94 commented

What I mean is that basically I had to increase fuel flow through the joints for fuel to travel, but this had not been done before, the transfers traveled perfectly in SU8.

An example between junctions would be:

Line.150 = Name:TT9LJuncToTT10LJunc#Source:TT9LJunc#Destination:TT10LJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.151 = Name:TT10LJuncToTT05SIVJunc#Source:TT10LJunc#Destination:TT05SIVJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.152 = Name:TT05SIVJuncToTT05IVJunc#Source:TT05SIVJunc#Destination:TT05IVJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.153 = Name:TT05IVJuncToTT06SIVJunc#Source:TT05IVJunc#Destination:TT06SIVJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.154 = Name:TT06SIVJuncToTT11LIVJunc#Source:TT06SIVJunc#Destination:TT11LIVJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.155 = Name:TT11LIVJuncToTT11LHYDJunc#Source:TT11LIVJunc#Destination:TT11LHYDJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.156 = Name:TT11LHYDJuncToTT11LJunc#Source:TT11LHYDJunc#Destination:TT11LJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.157 = Name:TT11LJuncToMJVLeft#Source:TT11LJunc#Destination:MJVLeft#FuelFlowAt1PSI:0.01#Volume:0.24

Line.158 = Name:TT9RJuncToTT10RJunc#Source:TT9RJunc#Destination:TT10RJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.159 = Name:TT10RJuncToTT07SIVJunc#Source:TT10RJunc#Destination:TT07SIVJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.160 = Name:TT07SIVJuncToTT07IVJunc#Source:TT07SIVJunc#Destination:TT07IVJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.161 = Name:TT07IVJuncToTT10SIVJunc#Source:TT07IVJunc#Destination:TT10SIVJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.162 = Name:TT10SIVJuncToTT08SIVJunc#Source:TT10SIVJunc#Destination:TT08SIVJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.163 = Name:TT08SIVJuncToTT11RIVJunc#Source:TT08SIVJunc#Destination:TT11RIVJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.164 = Name:TT11RIVJuncToTT11RHYDJunc#Source:TT11RIVJunc#Destination:TT11RHYDJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.165 = Name:TT11RHYDJuncToTT11RJunc#Source:TT11RHYDJunc#Destination:TT11RJunc#FuelFlowAt1PSI:20#Volume:0.24

Line.166 = Name:TT11RJuncToMJVRight#Source:TT11RJunc#Destination:MJVRight#FuelFlowAt1PSI:0.01#Volume:0.24

However, now to control the fuel that enter the tanks from this junctions would be:

Line.124 = Name:TT05SIVJuncToSIValve05#Source:TT05SIVJunc#Destination:SIValve05#FuelFlowAt1PSI:0.01#Volume:0.24

Line.125 = Name:TT06SIVJuncToSIValve06#Source:TT06SIVJunc#Destination:SIValve06#FuelFlowAt1PSI:0.01#Volume:0.24

Line.126 = Name:TT07SIVJuncToSIValve07#Source:TT07SIVJunc#Destination:SIValve07#FuelFlowAt1PSI:0.01#Volume:0.24

Line.127 = Name:TT08SIVJuncToSIValve08#Source:TT08SIVJunc#Destination:SIValve08#FuelFlowAt1PSI:0.01#Volume:0.24

Line.128 = Name:TT05IVJuncToIValve05#Source:TT05IVJunc#Destination:IValve05#FuelFlowAt1PSI:0.01#Volume:0.24

Line.129 = Name:TT07IVJuncToIValve07#Source:TT07IVJunc#Destination:IValve07#FuelFlowAt1PSI:0.01#Volume:0.24

As you can see between joints I am forced now to use 20PSI for fuel to travel, but when I reach a valve I have to lower the psi to 0.01 (because then I empty the tanks in seconds). This didn't happen before, I didn't even have to add anything.

#FuelFlowAt1PSI:0.1#Volume:0.24 is the default value according SDK, but in unions it no longer works and I am forced to add them with ridiculous values.

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Please let me know how the out come is. I still have issue with APU wiring for my B777/B767 mod. It only works when I turn FWD LEFT PUMP on (it should get fuel from Left Tank on the same Fuel Line like where that pump is connected)
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FlyingRaccoon avatar image
FlyingRaccoon answered OzWookiee commented

Hello @CodenameJack447

My apologies for not coming back to you earlier.
Thanks to your feedback, we have been able to reproduce the problem you've mentioned.
It occurs when one of the output lines of a junction is closed (if it leads to a closed valve for example) and will cause a drastic drop in fuel flow.

We have a fix for this but haven't made a decision yet on how we will handle this to avoid causing any regressions on existing products.

I'll come back to you when I have more information but I'd say if you don't plan to release the product you're working on before SU10, it's probably not worth trying to work around the issues you have with this on SU9.


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Hey @FlyingRacoon, Good to hear that there is a fix coming, but I'm curious about your comment:

"We have a fix for this but haven't made a decision yet on how we will handle this to avoid causing any regressions on existing products."

Unfortunately we are hit constantly with regression issues with every sim update, where something that worked previously no longer does. So why is that all of a sudden a concern now.

Sorry for the salt, but if something is wrong, it should be fixed, documented and your "partners" alerted of the change.

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That's what I meant in this comment. My apologies if this is not clear.

We identified the problem, have a fix for it, will deploy it in a way that causes no regression, and will communicate on what to change if you want to use the fixed version.

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OzWookiee avatar image OzWookiee FlyingRaccoon ♦♦ ·
Don't worry about regression LOL. Better documentation and communication ensures we can ALL fix the issues and ensure cleaner code on your end.
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CodenameJack447 avatar image
CodenameJack447 answered Leprechaulive commented

ok, I stay at peace then knowing that the problem is real and not mine. I managed to finish the actual fuel system for the F-15, and although it works, I had to do tricks to get the flowing fuel to its destination, although there are curiously lines between junctions where I measured not flowing fuel at all, but Interestingly there are fuel flow in the next line. I guess if you end up fixing it I won't have to make many changes later.

We have no choice but to wait since you have a more serious problem now and that is that we cannot compile projects since last patch, which has stopped production for many of us unfortunately.

I will only tell you one thing and I do not expect an answer, only that you reflect among yourselves: you must regain control of the situation, it is not normal that after each update aspects that worked perfectly, now are damaged, but also that you are not aware of it. Aspects that has nothing to do with what you are supposed to fix. This is without a doubt the update that has caused the most collateral and direct damage to everyone in general, to a point where the players do not enjoy it and neither do we.

You seem to schedule update releases without any apparent quality control over them and people have a limit.

It takes a lot to lift something from scratch and only a few seconds to destroy it if you're not careful about what you do.


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Specially considering that QA has been a problem since day one!

And as of this message we are at day one + 639......

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FlyingRaccoon avatar image
FlyingRaccoon answered

Hello everyone

Some more info on this issue.
With SU10, the issue with fuel flow dropping when junctions output lines are closed will be fixed.
We have added a fuel system version number in the cfg to let people decide if they want to stay on SU8, SU9 version or use SU10/Latest version.

Please come back to us on this platform if you encounter any issue when SU10 flighting starts.


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