Fuel Indications and capacity

[markturner1960]

 Working out the finer points of refueling, I started with empty wing tanks and 25% fuel internal. I got transfer complete and the eyebrow "Full" lights green at 12,670 Lbs indicated, but the dial was only blue to 7.5 on the guage. Also, did not get disconnected prematurely, so that is a no factor. 

Is this correct ? Just trying to get to know what is a full load in this loadout. Also, is there an indication when  they are empty? Thanks

Edited May 31, 2024 by markturner1960

[Czar66]

5 minutes ago, markturner1960 said:

  Also, is there an indication when  they are empty? Thanks

 

Annunciator Panel at Right Sub-Panel https://f4.manuals.heatblur.se/cockpit/pilot/right_sub_panel.html

Green lights for each tank means no fuel flow is detected.

[markturner1960]

Thanks, thats helpful. I have some further questions regarding the fuel system: ( I have read the manual section, but there is lots that is not clear or explained) 

1) When refueling, do the external tanks if carried fill first? Or is it the internal tanks first? 

2) What circumstances will result in no fuel being dumped when you turn on the wing tank dump switch? ( I had this happen) And does it function like the dump switch on other jets? If not, how? 

3) If carried, which external tanks empty first ? How is this controlled if required? Do they all auto transfer at the same time? At what fuel levels does the auto transfer kick in? 

4) The fuel totalizer only shows internal fuel, correct? If a full internal load is 12,800 lbs, and this is shown in the digital tape readout on the instrument, why is the curved dial indicator on the top of the instrument only showing 7.5 out of 10? 

5) The warning lights illuminate while autotransfer is taking place and then go off until the next cycle starts. Warning lights on for 2 minutes or more indicate the respective tank is empty...correct? 

 

 

 

[Zabuzard]

Thanks, thats helpful. I have some further questions regarding the fuel system: ( I have read the manual section, but there is lots that is not clear or explained) 
1) When refueling, do the external tanks if carried fill first? Or is it the internal tanks first? 
2) What circumstances will result in no fuel being dumped when you turn on the wing tank dump switch? ( I had this happen) And does it function like the dump switch on other jets? If not, how? 
3) If carried, which external tanks empty first ? How is this controlled if required? Do they all auto transfer at the same time? At what fuel levels does the auto transfer kick in? 
4) The fuel totalizer only shows internal fuel, correct? If a full internal load is 12,800 lbs, and this is shown in the digital tape readout on the instrument, why is the curved dial indicator on the top of the instrument only showing 7.5 out of 10? 
5) The warning lights illuminate while autotransfer is taking place and then go off until the next cycle starts. Warning lights on for 2 minutes or more indicate the respective tank is empty...correct? 
 
 
 

1) The fuel is balanced to all tanks simultaneously. There are bottlenecks though depending on line-diameters and pressure. For example, it can distribute quite well between all internal tanks, but it can't pump the same amount of fuel into the wing tanks or ext tanks, instead it is distributed there. So for example if all internal tanks get X fuel, the two wing tanks get roughly X/2 fuel at the same time. It cant be said in general though, as its all computed and simulated to a very deep level.

2) The phantom can only dump from the two wing tanks. Once they a empty, no fuel can be dumped anymore.

3) You select either outboard, center or off (wing tanks) using the triangle switch. It will fill tanks 1 (but that one is usually full anyways bc filled from internal tanks as well), tank 3 and 5. So whenever they go below a threshold, the selected ext tanks kick in and fill them up again. This repeats forever until the selected ext tanks are empty. "Auto transfer" is an emergency mode that kicks in when tank 1+2 are low (iirc 2300 lb), that happens at roughly 3k lbs total (unless u trapped wing fuel). In this mode the aircraft ignores all your switch settings and forces all fuel from anywhere into tank 1.

4) The number on the totalizer is the internal fuel including wing tanks and tank 7 (reserve). The tape above is only tanks 1 to 6. So it misses the reserve tank and both wing tanks. (and both are missing the ext tanks)

5) The mentioned ext tank lamps indicate when someone requests fuel from the ext tanks (opens the valve) while not getting any fuel from them (no flow sensed). The valve is opened in said emergency mode (auto fuel transfer), when the AAR door is opened and also when you selected it for transfer using the triangle switch. But you can't differentiate the lamp being on from the normal situation that tanks 1, 3, 5 are full and hence dont accept any fuel from the ext tanks. The lamps must be on for like 2mins without interruption to safely assume that the ext tanks are likely empty. Also, the fuel totalizer dropping below values where its clear that the ext tank didn't refuel anything anymore.

[markturner1960]

OK, thanks, its a little clearer.......I must say, it does seem unecessarily convoluted and unintuitive, doesnt it? Whats wrong with having a fuel guage that has a scale that measures 0 - 20,800, is marked at internal (12,800), centreline and external wings, and having a simple light that illuminates for each external tank once empty? Then you would easily know at a glance what fuel you had and what was empty.......Probably designed by the same guy that decided where all the guages went in the cockpit......

When refueling then, there is no real certain way to see exactly what fuel you have and when you are fully topped off, is there? Thats crazy......

Edited June 1, 2024 by markturner1960

[Phantom711]

vor 35 Minuten schrieb markturner1960:

Whats wrong with having a fuel guage that has a scale that measures 0 - 20,800, is marked at internal (12,800), centreline and external wing

Well…because it would require measuring equipment in the external tanks and the respective wiring to report it to said gauge in the cockpit.

[=475FG= Dawger]

The Phantom fuel system is very simple from the pilot’s perspective. 
 

The counter shows total internal fuel like it is one big tank. 
 

The tape excludes some internal tanks.(Wing tanks)

Why? 

There is a switch to turn off internal wing tank transfer, leaving you with only the fuel on the tape to work with. 
 

You can ignore the tape during normal operations. 
 

If External Tanks Full lights are on and you see ~ 12K lbs on the counter, you are full. 

[Zabuzard]

Yeah, the fuel gauge and system is complex if you, as a pilot really care about how it all works under the hood.
In practice, usually knowing the total fuel level is enough and I guess that is what they mostly cared about when designing it.

Btw, there is a small hidden switch (Feed Tank Test) behind the Tail Hook lever to show the fuel in tank 1, the most important tank, as any fuel in the system goes through that tank and then into the engines.

It is indeed annoying that you don't get to know much about the ext tanks and that is indeed mostly contributed to them not having any sensoring equipment installed.
Well, they do have one sensor, that is a small swimmer will eventually press a button on the top when the tank is full. Leading to the ext tank FULL lights illuminating on the top left of your canopy bow (whenever the aar door is open or ground refueling happens).

[markturner1960]

Yeah, ggod points......I guess in time, it will all seem normal and I wont think anymore about it....its just the shock of the new! Thanks!

[Kalasnkova74]

13 hours ago, markturner1960 said:

OK, thanks, its a little clearer.......I must say, it does seem unecessarily convoluted and unintuitive, doesnt it? Whats wrong with having a fuel guage that has a scale that measures 0 - 20,800, is marked at internal (12,800), centreline and external wings, and having a simple light that illuminates for each external tank once empty? Then you would easily know at a glance what fuel you had and what was empty.......Probably designed by the same guy that decided where all the guages went in the cockpit......

When refueling then, there is no real certain way to see exactly what fuel you have and when you are fully topped off, is there? Thats crazy......

 

You should see how other organizations handled this. The MiG-23 uses a totalizer that’s set by the crew chief with the amount of liters pumped into the jet. The cockpit “fuel gauge” uses a flow measurement device which deducts from the totalizer how much fuels been pumped through that pipe. If a situation arises where a fuel tank is punctured or leaking, the Floggers fuel gauge will be of little help. 

[felixx75]

https://youtu.be/2u2yLEM1iHM?si=AqrW6aDpRqur2P5Z