Su-25T fuel tanks

[mastershotgun]

Hi Guys,

 

 

So, I was trying to figure out how much those things weight...

 

 

Based on the load manager, fully fueled Su-25T weights 15286kg and fully fueled Su-25T with 2x fuel tank weights 16806kg... Oki, so if you subtract and divide you will get that the single tank full with fuel weights 760kg. That sounds plausible.

 

 

Now the puzzling stuff. The completely empty Su-25T weights 11496kg and completely empty Su-25T with 2x fuel tank weights 13016kg which after calculation also makes 760kg :huh: And I'm sure that the tanks are empty, because of the fuel indicator in cockpit and you cannot start the engines...

 

 

Is it a bug or am I doing something wrong?

[Harker]

The fuel bar in the Mission Editor is for internal fuel only. The external tanks are mounted always full, unless otherwise stated in their description. When you reduce the internal fuel to 0, you should still see a Fuel Weight on the line below that is above 0 and it corresponds to the fuel contained in the external tanks.

 

The reason you cannot start is likely because you don't have any internal fuel and so the engine feed tanks are empty, plus you need to turn on the battery (RShift+L, I think). I just tried it and the fuel indicator started going up as soon as I turned on the battery, because fuel started transferring from the tanks and then I could start normally.

[mastershotgun]

NO, I'm not talking about the mission editor...

 

I used the load out manager in the game, when you are in the cockpit already and the dashboard fuel gauge in your cockpit for the measurement.

[Harker]

NO, I'm not talking about the mission editor...

 

I used the load out manager in the game, when you are in the cockpit already and the dashboard fuel gauge in your cockpit for the measurement.

Still, the same logic applies. If you set the fuel slider to 0 on the rearm/refuel menu, that's still only for the internal fuel. If you have electric power on, you should see fuel transfer taking place from the external to the internal tanks. If you don't have electric power on, the fuel indicator doesn't work. The Su-25T doesn't have the option of mounting empty external tanks in the sim.

[mastershotgun]

Well in that case something is not working...

 

 

The plane with 0 flares, 0 chaff, 0 ammo and 0 fuel weights 11496kg

The plane with 0 flares, 0 chaff, 0 ammo, 0 fuel and 4x fuel pods weights 14536kg

 

 

That makes one pod weights 760kg which is what the full pod should weight.

 

 

Now the weird part

 

 

The plane with 0 flares, 0 chaff, 0 ammo and 100% fuel weights 15286kg

The plane with 0 flares, 0 chaff, 0 ammo, 100% fuel and 4x fuel pods weights 18326kg

 

 

Which makes single pod weight 947.5kg

 

 

And this is just the numbers from the load manager from the cockpit, not the mission editor....

[mastershotgun]

And another weird thing...

 

 

Single pod should have 620kg of fuel, so when I empty the plane my dashboard gauge says 0kg of fuel. Good. Now I load my plane with 0% fuel and 4x fuel pods and dashboard gauge says 2830kg of fuel which makes 707.5kg of fuel per pod...

 

 

So, I'm wandering what is going on? Do they model, that not all the pods may have the exact amount of fuel? Or maybe the gauge is not 100% accurate? Or is the Windows calculator broken?

[Ironhand]

Well in that case something is not working...

 

 

The plane with 0 flares, 0 chaff, 0 ammo and 0 fuel weights 11496kg

The plane with 0 flares, 0 chaff, 0 ammo, 0 fuel and 4x fuel pods weights 14536kg

 

 

That makes one pod weights 760kg which is what the full pod should weight.

 

 

Now the weird part

 

 

The plane with 0 flares, 0 chaff, 0 ammo and 100% fuel weights 15286kg

The plane with 0 flares, 0 chaff, 0 ammo, 100% fuel and 4x fuel pods weights 18326kg

 

 

Which makes single pod weight 947.5kg

 

 

And this is just the numbers from the load manager from the cockpit, not the mission editor....

You did the math wrong in the last part. subtracting the pod weights out, I come up with 760 for each pod. 18326-3040=15286

[mastershotgun]

You did the math wrong in the last part. subtracting the pod weights out, I come up with 760 for each pod. 18326-3040=15286

 

 

Aaaa you are right on this one... I messed my numbers :D on this one

 

 

You see this is why it pays to double-check everything before you start flame wars and submitting tickets like crazy...

 

 

But! the other one still stays!

[mastershotgun]

And another weird thing...

 

 

Single pod should have 620kg of fuel, so when I empty the plane my dashboard gauge says 0kg of fuel. Good. Now I load my plane with 0% fuel and 4x fuel pods and dashboard gauge says 2830kg of fuel which makes 707.5kg of fuel per pod...

 

 

So, I'm wandering what is going on? Do they model, that not all the pods may have the exact amount of fuel? Or maybe the gauge is not 100% accurate? Or is the Windows calculator broken?

 

 

This one is still on. Could somebody verified me on this one as well? Thank you!

[Ironhand]

And another weird thing...

 

 

Single pod should have 620kg of fuel, so when I empty the plane my dashboard gauge says 0kg of fuel. Good. Now I load my plane with 0% fuel and 4x fuel pods and dashboard gauge says 2830kg of fuel which makes 707.5kg of fuel per pod...

 

 

So, I'm wandering what is going on? Do they model, that not all the pods may have the exact amount of fuel? Or maybe the gauge is not 100% accurate? Or is the Windows calculator broken?

 

In the pit, I get 2465 which translates to 616.25. I'm basing that on the numerical readout, not the bar. The bar is showing a bit over 2500, though the normal viewing angle makes it look more than that. Not sure what happened to 3.75 kg from each but not something I'm particularly worried about.

 

EDIT: Ahh...The "extra" fuel is actually the fuel line bar. Notice the thick white line you see with "0" fuel:

 

 

Subtract that from the bar height and the numerical readout matches.

Edited March 6, 2020 by Ironhand

[mastershotgun]

In the pit, I get 2465 which translates to 616.25. I'm basing that on the numerical readout, not the bar. The bar is showing a bit over 2500, though the normal viewing angle makes it look more than that. Not sure what happened to 3.75 kg from each but not something I'm particularly worried about.

 

 

Hmmm That is interesting, because I read mu value form the number not the bar as well... I would like to see test from more people, but is it actually possible that they really put little bit of randomness into it? :huh:

[Ironhand]

Hmmm That is interesting, because I read mu value form the number not the bar as well... I would like to see test from more people, but is it actually possible that they really put little bit of randomness into it? :huh:

 

I doubt it. I'd check your setup again. The only variation would be due to temperature and I doubt they do that either.

 

Oh, and check my edit in my previous message.

[mastershotgun]

I doubt it. I'd check your setup again. The only variation would be due to temperature and I doubt they do that either.

 

Oh, and check my edit in my previous message.

 

 

Yea I'm reading the number. I just did another test. Here is what I got...

 

 

[Ironhand]

Yea I'm reading the number. I just did another test. Here is what I got...

 

This is what I see with no internal fuel and 1 external tank and the numbers held as I added tanks:

 

 

 

I've atttached the mission for you to play with. I'm off to a wedding for the rest of the weekend. But I'll check to see what you've found at some point.

Su-25T 1 External Tank.miz

[mastershotgun]

Well, in that case, I must have premium pods or something... Got another test and when I start adding pods one by one and my results are now quite different... This why I was thinking about the randomness

 

 

 

1 pod 810kg

2 pods 1640kg (+830)

3 pods 2255kg (+615)

4 pods 2875kg (+620)

 

 

PS: fist two pods were on the outer pylons, it should not make difference, but it seems it does...

[Ironhand]

Well, in that case, I must have premium pods or something... Got another test and when I start adding pods one by one and my results are now quite different... This why I was thinking about the randomness

 

 

 

1 pod 810kg

2 pods 1640kg (+830)

3 pods 2255kg (+615)

4 pods 2875kg (+620)

 

 

PS: fist two pods were on the outer pylons, it should not make difference, but it seems it does...

Interesting. Do you get the same 1 tank value from the mission I uploaded? I wonder if this is a matter of sim version. I’m looking at this on the OB. Not at home. So I can’t check this out myself on the Release version.

 

For chuckles, you might want to upload your mission and I can look at it Monday.

[mastershotgun]

From your mission I get the same value you have on the screenshot...

 

 

And here is what happened when I start adding tanks to you mission

 

 

2nd pod added to the other inside slot 1630kg (+1025)

3rd pod outside slot 2255kg (+625)

4th pod other outside slot 2880kg (+625)

[Ironhand]

From your mission I get the same value you have on the screenshot...

 

 

And here is what happened when I start adding tanks to you mission

 

 

2nd pod added to the other inside slot 1630kg (+1025)

3rd pod outside slot 2255kg (+625)

4th pod other outside slot 2880kg (+625)

Well, for whatever reason, we are getting two different results. Either one of us has a screwed up installation or we are using different methodologies. Here's what I get for the ME and Cockpit values. There is always 15 kg missing which is not additive. I assume it has something to do with filling the internal plumbing.

 

[Jonne]

Just as a thought, the F-14 fuel gauge has an error of 600lbs, which is AFAIK simulated.

 

Apart from that, fuel level gauges are generally very unreliable and usually do not compensate for density changes.

[Ironhand]

True. Then again, though all of this I haven’t noticed any random changes. The numbers always come out the same on my end. And, that’s true even when I tested at temperature extremes.

[draconus]

It might be that mastershotgun was using refuel/rearm window to see dynamically changed weight which is bugged afair. ME calculation should be fine.

Btw: Tomcat doesn't have 600lbs error. It's much smaller and its tanks are empty at 300 - not usable amount because of how the tank is built.

 

Edit: I don't see any bugs in rearm/refuel window wrt weights.

Edited March 10, 2020 by draconus

[Ironhand]

It might be that mastershotgun was using refuel/rearm window to see dynamically changed weight which is bugged afair. ME calculation should be fine...

If so, there’s the difference in methodology... :)

[draconus]

I played around with ME, Ironhand's mission file and refuel/rearm in 2.5.6. Generally I get what Ironhand get.

The tricky part is refuel/rearm. It has its quirks. It doesn't work like in ME. It assumes external tanks fuel as total fuel in percentage. You can't really get to the point of having both fuel tanks and 0% fuel total. Sounds logical. Even if you move the slider to 0% and keep the tank you will still end up with fuel like 16%. If you get rid of the tanks and go for 0% you end up with 2% and have to ask again to clean it to 0%. There's also this transfer from externals to feed tanks when you turn on the power. If you ask for more tanks during this process you will get new full tanks plus what was already transfered. Lots of error points to make so yeah, not good method for counting gas.

[mastershotgun]

Oki, as I mentioned I did not use the ME at all, all my measurements were done strictly refuel/rearm...

 

 

Also I noticed that when I had a tank I always got a new one when adding another... So when I set fuel to 0% add a tank, hit ok it give me the fuel... Open the refuel/rearm window again and have some % of fuel, set it again to 0% add additional tank, hit ok, my previous tank was replaced with new full one, got additional one and so... they always replaced the old tanks with new full ones...

[mastershotgun]

PS: all my measurement are done in the 2.5.5 stable version not the beta if it makes a difference...