[2.9.21.16362] Question about specific air refueling behaviour

[Stickler]

Compare the attached tracks. Both show me in an identical aircraft (airspawn with empty centerline tank) during AAR.

Scenario 1 (AAR_EFB_wings): Spawn fuel 3725 lbs.

• The centerline tank starts filling up immediately upon contact.
• The internal wing tanks start filling up only once fuselage cells 1, 2 and 7 are full.

Scenario 2 (AAR_EFB_wings_centerline): Spawn fuel 6155 lbs.

• Both the internal wing tanks and the centerline tank start filling up immediately after contact even though cell 7 is empty/still in the process of being topped off.

Why is cell 7 being full an apparent prerequisite for the internal wing tanks starting to fill up in scenario 1, but not in scenario 2?

AAR_EFB_wings.trk

AAR_EFB_wings_centerline.trk

Edited Saturday at 09:03 PM by Stickler

[Zabuzard]

Eh, so this is a bit complex to explain. Essentially, it is due to the refueling pipe layout. There are no controllers or anything that open and close valves to execute the refueling in a coordinated manner, the refueling door is essentially connected to every tank with a specific pipe layout and it just presses the fuel through that, the rest is down to fluid physics, so to speak.

The resulting outcome is a play of pressure, pipe diameters and lengths, gravity and G-forces depending on how much height the pipes have to cover and so on. Especially pressure in the other pipes change as soon as a tank fills up, more fuel will then reach to other tanks through the pipes. Or in other words, the more tanks you have that are full or filling up, the more fuel will be able to reach to tanks that are further down the pipe layout. Because it is so complex, I cant really do the math in detail now to show you why it ends up the way it is, but I can give you some insights into the pipe layout that should give a good idea of why you see what you saw.

The pipe layout looks something like this:

This doesnt mean it will be refilled in that order, like "Tank 1 first until full, then tank 2 until full, ..." but they are connected in that order. There is only so much fuel being pressed down the pipes and when for example tank 1, 2, 3, 4, 5 are all almost empty, then the final fuel pressure that far down the pipe layout will reach close to zero and the tanks at the end wont get anything just right now. Once the tanks that hierarchically come first slowly fill up, more and more pressure will still be available for the tanks further down the line.

There are also limits of how much fuel can actually be pressed through these pipes, they arent individually capabable of supporting all the fuel at the maximum refueling rate. So once you for example are down to just filling up, lets say the two external wing tanks, then you are bottlenecked by what these two pipes can support. Hence why refueling only those two takes so long then.

Edited 12 hours ago by Zabuzard

[MAXsenna]

It really looks like of one of those quiz games one can find.

[speed-of-heat]

i get content not viewable in your region?

 

[MAXsenna]

i get content not viewable in your region?
 

It's probably posted on Imgur, which has blocked the UK, which has sued Imgur for not implementing age verification. Sigh... The Internet is coming to and end in the Western world, and we'll all be on VPNs in the future. Politics!

Sent from my SM-A536B using Tapatalk

[speed-of-heat]

roger that

[Zabuzard]

Oof, wait ill upload it directly to the forum... try again

Edited 12 hours ago by Zabuzard

[speed-of-heat]

Thank you now I can see it !