Time to AAR pretty long (?)

[Lt_Jaeger]

My feeling might be off here, since I usually only tank the Tomcat, but if I recall right, the times I used a DCS module on the boom, it was filled up pretty fast. 

Today, in MP, we did a AAR. All 4 of us were pretty amazed how long it took to fill her up. I went with roughly 11k on the tanker, had two wing bags and it took forever to fill up. 

Is my (our) feeling off, or does it really take a long time to fill her up? 

Edited June 8, 2024 by Lt_Jaeger
spelling

[ondro1911]

the whole refuelling process is somehow very long, even when refuelling on the ground

[AdrianL]

17 hours ago, Lt_Jaeger said:

roughly 11k on the tanker

So, according to the manual, that would have taken slightly under 3 mins. At a rate of up to 3900 lbs per minute

https://f4.manuals.heatblur.se/systems/engines_and_fuel_systems/fuel_system.html#air-refueling-system

[Zabuzard]

Note that external tanks are not shown on the totalizer. So if you refuel these as well, it will take much longer.

[diditopgun]

I found it extremely long too. It clearly doesn't transfer at 3900ppm... Going from 7000lbs to 9000lbs took me severals minutes without disconnection. (no external tanks)

[Flia]

Same here. I also think it takes too long to refuel.

Edited May 25, 2024 by Flia

[markturner1960]

12 hours ago, Zabuzard said:

Note that external tanks are not shown on the totalizer. So if you refuel these as well, it will take much longer.
 

Hi Zabzuzard, can you explain why the time taken to “fully refuel” can vary between one minute and three? I would have thought the transfer rate was constant, this suggests it is variable? What controls these variables ? Or do you mean it’s one minute for a full internal load and 3 minutes for full internal plus all tanks?
Also, Jester…..the running total call outs given in the F14 are very useful………why does Jester not give them in the F4? Glancing at the gauge is not a good idea as you need all your concentration to anticipate any movement and also, it’s tricky to actually read the gauge without zooming in anything other than direct illumination. 
 

Final refueling niggle: Why do we have to cycle the door if you come off the boom? Surely not the same in reality and I just can’t see the point of this?

Edited May 26, 2024 by markturner1960

[Zabuzard]

Hi Zabzuzard, can you explain why the time taken to “fully refuel” can vary between one minute and three? I would have thought the transfer rate was constant, this suggests it is variable? What controls these variables ? Or do you mean it’s one minute for a full internal load and 3 minutes for full internal plus all tanks?
Also, Jester…..the running total call outs given in the F14 are very useful………why does Jester not give them in the F4? Glancing at the gauge is not a good idea as you need all your concentration to anticipate any movement and also, it’s tricky to actually read the gauge without zooming in anything other than direct illumination. 
 
Final refueling niggle: Why do we have to cycle the door if you come off the boom? Surely not the same in reality and I just can’t see the point of this?

The WSO in the Phantom has no fuel gague, he cannot give you callouts.

The AAR door must be cycled to reset the refueling system, that is exactly how it works in reality as well. By the way, you have the same behavior in the A-10C.


Regarding the refueling speed, we will have a look to check if it matches what its supposed to be. Cheers.

[markturner1960]

I see! Thank you! Although, you did not answer the first question ? Does it vary for a set amount currently or are times mentioned in the manual for minimum and maximum loads? Thanks again

[Zabuzard]

I see! Thank you! Although, you did not answer the first question ? Does it vary for a set amount currently or are times mentioned in the manual for minimum and maximum loads? Thanks again

It can vary if the only tanks that need fuel are far from center. The fuller you are, the longer it takes to top off. But these effects are fairly minimal overall.

The fuel system is complex and provides plenty of pitfalls and opportunities for misinterpretation.

As mentioned, we will investigate :)

[markturner1960]

Can I follow up with another query, once the internal guage registers full, how do you know when the tanks are topped off, if carried? 

[Raven (Elysian Angel)]

3 minutes ago, markturner1960 said:

Can I follow up with another query, once the internal guage registers full, how do you know when the tanks are topped off, if carried? 

The canopy bow lights will indicate that

[markturner1960]

OK, so the guage will register full (11,00lbs?) and then you would carry on filling and when tanks are full, the canopy bow lights illuminate. Correct? Do they only illuminate when tanks are being used? 

[Zabuzard]

Thank you for the reports. Today, I have investigated the refueling process extensively and found and fixed the following issue:
The part of the pipe system right at the refueling door to where it splits up to the tanks had a too small diameter. This resulted in the top refueling rate being rather 2400 lbs/min instead of 3900 lbs/min. This has now been fixed. The max refuel rate is now correctly 3900 lbs/min.
However, note that the actual refuel rate in practice is highly dynamic and depends on the tanks that still need fuel. This is due to the pipe layout. For example, the left and right ext tanks share a pipe, resulting in the fuel flow to them being bottlenecked from what is theoretically possible at max pressure.
In practice, this means that while all your tanks still need fuel, you achieve 3900 lbs/min. Once you are down to just L/R ext tanks, it is more like 1400 lbs/min.
So topping off your internal tanks 1-7 can now be done in 1min instead of 2min. But from there on, you still need ~4min to fill up LR wing + LR ext tanks. Total time to refuel in this situation is about 5-6min (while connected all the time, obviously). Note that if you have to use burner while disconnected, the time will get longer.

Edited June 13, 2024 by Zabuzard

[Torbernite]

2024/6/13 PM9点57分，Zabuzard说：

Thank you for the reports. Today, I have investigated the refueling process extensively and found and fixed the following issue:
The part of the pipe system right at the refueling door to where it splits up to the tanks had a too small diameter. This resulted in the top refueling rate being rather 2400 lbs/min instead of 3900 lbs/min. This has now been fixed. The max refuel rate is now correctly 3900 lbs/min.
However, note that the actual refuel rate in practice is highly dynamic and depends on the tanks that still need fuel. This is due to the pipe layout. For example, the left and right ext tanks share a pipe, resulting in the fuel flow to them being bottlenecked from what is theoretically possible at max pressure.
In practice, this means that while all your tanks still need fuel, you achieve 3900 lbs/min. Once you are down to just L/R ext tanks, it is more like 1400 lbs/min.
So topping off your internal tanks 1-7 can now be done in 1min instead of 2min. But from there on, you still need ~4min to fill up LR wing + LR ext tanks. Total time to refuel in this situation is about 5-6min (while connected all the time, obviously). Note that if you have to use burner while disconnected, the time will get longer.
 

Hi Zabuzard! Thanks for your job!

Could you please provide some figures of your modeled fuel system to show the refueling sequence and flow? After reading original manual, I took 2 AAR tests and got confused.

 

TEST 1:

AAR from about 2100lbs to full INT+EXT WINGS.

A high transfer rate of around 3900lbs/min was observed during 3000-8000lbs as stated. But high transfer rate was kept beyond 8000lbs to nearly 9000lbs before obvious slow down.(According to the manual T-O-1F-4E-1(1979), aircrafts before blk41 have 12896lbs INT fuel and 8800lbs in fuselage tank 1-7, while those after blk41 have around 12000lbs INT fuel with a capacity of a bit less than 8000lbs in fuselage tank 1-7. The latter should be our version. But the tested value in game above is closer to the fuselage tank capacity of the earlier version in manual.)

After that, the INT WING tanks were filled simultaneously with EXT WING tanks, and over 4mins were taken to fill them as stated. EXT WING tanks full lights were on before full INT fuel was indicated.

 

TEST 2:

INT ONLY AAR from about 2100lbs to full INT.

Same rate as TEST 1, before and after fuselage full. Roughly same time was needed as TEST 1, only seconds shorter. (I think maybe it's because INT WING tanks filling rate is independent from EXT WING tanks and has its own limit? But that seems inconsistent with the figure FO-2 in the manual.)

After INT full achieved, no automatic disengage happened. Boom had to be manually disengaged with button on the stick and tanker called "transfer complete". The fuel indicator showed consumption not immediately after disengagement but with a short time interval.

 

Besides, according to the figure FO-2 in the manual, the AAR fuel is transferred into tank 1, 3 and 5 directly. While in our manual it's stated that "Fuel received is delivered into fuselage cell 2, then equalized through the rest of the aircraft cells, wing tanks, and, if installed and selected, external tanks."

 

Can you confirm whether these features are all correct as it is? Thank you!

F4EAARINTonly.trk F4EAARINTnEXTWING.trk

[Zabuzard]

The fuel system is accurately modelled and has all these features you mention.

It is difficult to see as a user because you are lacking the debug interface showing all individual tanks in-flight.

Perhaps one of the devs can rerecord your tracks with it open, then you can see whats actually happening underneath

Probably also a good idea for a modder to add that through Jester Modding, reporting fuel tank state through the Jester Console.

[Torbernite]

2小时前，Zabuzard说：

The fuel system is accurately modelled and has all these features you mention.

It is difficult to see as a user because you are lacking the debug interface showing all individual tanks in-flight.

Perhaps one of the devs can rerecord your tracks with it open, then you can see whats actually happening underneath

Probably also a good idea for a modder to add that through Jester Modding, reporting fuel tank state through the Jester Console.

Thank you for the reply!

I just found I misunderstood the transfer sequence. I wrongly thought the INT WING tanks were not being filled before fuselage full and didn't notice the fuselage indication tape. So "the drop of transfer rate happens beyond 8000lbs" looked strange to me before.

[Zabuzard]

11 hours ago, Torbernite said:

Thank you for the reply!

I just found I misunderstood the transfer sequence. I wrongly thought the INT WING tanks were not being filled before fuselage full and didn't notice the fuselage indication tape. So "the drop of transfer rate happens beyond 8000lbs" looked strange to me before.

Illustrated a bit simplified it works like this:

The wing tanks left and right share one pipe. The ext tanks left right share one pipe. The center ext tank is independent. Tank 1, 3 and 5 receive fuel and share a pipe.  Tanks 2, 4, 6 and 7 receive through gravity feed, 7 behind 6. 

And all that is pressurized etc and pipe diameters and whatnot count as well.

The full refuel rate can only be measured right at the AAR door when the fuel can be squeezed through all the pipe sections still, i.e. all sections in the layout are still hungry for fuel. If that's not the case the refuel rate goes down bc your bottlenecked in the distribution.

The simulation depth on this system is very detailed. For example, gravity feed is computed individually with the exact 3D position of the connection (being at the bottom of the tank), the local G-vector at this position and the fluid level and "angle" in the tank and the resulting pressure force (for example if you dive nose down or fly negative G the fuel sips in the other direction and so on). Similar for the transfer through the pipes, the local pressure difference is computed per pipe based on diameter, length, fluid density and more.

The outcome in practice is highly dynamic and without per-tank debugging u can't really see the complexity that is simulated.

Edited May 3 by Zabuzard

[Torbernite]

30分钟前，Zabuzard说：

Illustrated a bit simplified it works like this:

The wing tanks left and right share one pipe. The ext tanks left right share one pipe. The center ext tank is independent. Tank 1, 3 and 5 receive fuel and share a pipe.  Tanks 2, 4, 6 and 7 receive through gravity feed, 7 behind 6. 

And all that is pressurized etc and pipe diameters and whatnot count as well.

The full refuel rate can only be measured right at the AAR door when the fuel can be squeezed through all the pipe sections still, i.e. all sections in the layout are still hungry for fuel. If that's not the case the refuel rate goes down bc your bottlenecked in the distribution.

The simulation depth on this system is very detailed. For example, gravity feed is computed individually with the exact 3D position of the connection (being at the bottom of the tank), the local G-vector at this position and the fluid level and "angle" in the tank and the resulting pressure force (for example if you dive nose down or fly negative G the fuel sips in the other direction and so on). Similar for the transfer through the pipes, the local pressure difference is computed per pipe based on diameter, length, fluid density and more.

The outcome in practice is highly dynamic and without per-tank debugging u can't really see the complexity that is simulated.

Thanks I got it now!

I marvel at your efforts to bring this great simulation. Thank you all for your job!