Fuel Tank Issue

[jgf]

I have an aircraft with six fuel tanks, all seem properly configured in the cfg file -

 

[fuel]
LeftMain  = 0.000, -6.000, 0.000, 24.000, 0.000
RightMain = 0.000, 6.000, 0.000, 24.000, 0.000
Center1= -10.000, 0.000, 0.000, 49.000, 6.000
Center2= 5.000, 0.000, 0.000, 29.000, 3.000
LeftAux= 0.000, -6.000, 4.000, 24.000, 0.000
RightAux= 0.000, 6.000, 4.000, 24.000, 0.000
fuel_type = 1                      //Fuel type: 1 = Avgas, 2 = JetA
number_of_tank_selectors = 1            
electric_pump=1

 

I can juggle the amount in each in the Payload/Fuel menu, but when flying switching to either Left Aux or Right Aux causes the fuel gauge to indicate zero.  How do I access that extra 48gal?

[defaid]

This may be off track but, if the fuel really is disappearing and it's not a fault with the gauge itself, then Shift+Z fuel % should drop when you switch tanks. If you can't see a change there, check Alt+A,F,F before swapping tanks and again after.

 

I have no idea where fuel consumption is modelled but that should give some pointer to what to look at next.

 

D

[ScottishMike]

It's a common issue with many panels. It is a panel issue, take the TDS 737 max9 (to be topical):

Actual fuel:

Panel reporting 0 fuel left and right (no gauge for centre tank), but as dafaid mentions ctrl Z will give you the actual total % fuel remaining.

The fuel is there and despite indicating 0 on the two fuel gauges the aircraft will happily fly on with the 62% remaining in the centre tank.

Unless you have a panel that allows you to select individual tanks FS9 uses fuel from outer tanks first then working it's way to centre tanks.

I guess it's a question of matching the panel to the aircraft. In the plane you mention does the panel allow you to select each of the 6 tanks individually?

If the panel allows you to select ALL tanks I leave it at that, letting FS9 use fuel from outer to inner tanks.

On some panels, usually general aviation craft, I hate it if they only have a right or left tank selector. I always forget to switch tanks every 5 minutes or so to keep the CG central.

[jgf]

The fuel switch has seven positions - Main, Aux, L Main, R Main, L Aux, R Aux, and Off (Main and Aux correspond to Center 1 and Center 2 in the cfg file).  Normal procedure is to start with L & R Main, then L & R Aux, then Aux, finally Main.  The fuel gauge is calibrated to 50 gallons at full and monitors whichever tank is selected.

 

I think fuel draw is rather odd, based on watching the gauge;  selecting either main tank I can fly over a hundred miles and the gauge barely moves, the next hundred miles it plummets to near empty, switch to either Aux tank and they are empty.  But, I can start on an Aux tank, fly around a hundred miles and watch the gauge steadily decrease, switch to a Main tank and it is full.  So it appears that when selecting either Main tank fuel is used from the corresponding Aux tank first, then the Main tank (this would account for the non linear gauge reaction);  but when selecting an Aux tank first fuel is drawn from it and the gauges reads properly, when it is near empty switch to the Main tank.  But either way all the fuel is used.  (I wonder if there is some way to make it work "properly", draw fuel only from the selected tank.)

 

" I always forget to switch tanks every 5 minutes or so to keep the CG central. "

 

Necessary in this aircraft, a five gallon imbalance and it wants to fly in circles.

[defaid]

That's a novel design flaw. I wouldn't say bug -- it sounds like the gauge is correctly reporting the main tank contents while the plane has an auto tank-select that always drains the aux first. I guess the switch is not a fuel tank selector but only a gauge controller.

 

Have you thought of looking for a downloadable popup gauge, or panel of tank-specific gauges? If you can't find one, the logical way to use the existing gauge is to start with it showing the aux contents and switch it to show main when the aux tanks are empty.

 

The Captain Sim C-130 has a great bug where 8 fuel tanks feed the four engines. The plumbing is such that four of the tanks each feed their own engine when all the crossfeeds are off. With the crossfeeds allowing universal flow, each tank supplies all four engines. So far, so logical.

 

But each tank supplies *all four* engines so the fuel consumption is quadrupled.

 

I have to shut off all the crossfeeds and do a manual tank to tank transfer (Alt+A F F) mid-flight.

 

D

 

[jgf]

It is a tank selector in that it draws fuel from the selected tank, only when selecting L or R Main it seems to draw from the corresponding Aux first;  selecting Main, Aux, L Aux, or R Aux draws fuel only from the selected tank.  So the oddity is that if I select, for example, the L Main tank the gauge shows the proper 24 gal there but is drawing from the L Aux, only when that tank is empty and fuel is now coming from the L Main does the gauge start dropping ...if it gets to zero the engine dies. 

 

And even this is a simplification of the actual aircraft fuel system, where there is a single fuel level gauge and two switches involved in selecting the six tanks;  current pilot reports virtually curse having to remember the proper sequences of the switches to balance fuel use without inadvertently switching to an empty tank.

 

But as long as I'm getting all the fuel I'm satisfied, just remember that selecting Main tanks first means the Aux tanks are empty when the gauge first starts dropping.

[TomPenDragon]

It's been a while since I've spent much time in the SimTech Staggerwing, and a lot of that has to do with the fuel situation.  If any plane needs automatic fuel balancing, it's that one - I don't have anything else that's as sensitive to an inbalance.  Since the gauge is .xml, I've tried tweaking the tank switcher to use "All", but no matter what I do, it still wants to run on the tank it wants and changing the code just screws up the fuel gauge.  Looking at my aircraft.cfg, I'm seeing that I just commented out the other tanks, put Left Main dead center (0,0,0) and put the full 180 gallons into it, switched the fuel gauge, and dropped the old one and the tank switcher in the trash (using the space in the VC for the switcher as a panel for switches with actual labels).  I'm not even a duffer when it comes to XML, so you might have better success with the rather convoluted (to an untrained eye) code of the switcher and fuel gauge.  I think SimTech was trying to do something really sophisticated and almost got it perfect...

 

Hope this helps!

[jgf]

The simplest solution would be to just make Center1 (the "Main" tank on the switch) a 174 gallon tank, empty the others and ignore them.  Another option is using an AP with a wing leveler.  But I like maintaining the realism and switching the tanks, means I can't just activate the AP and leave.

[TomPenDragon]

3 hours ago, jgf said:

The simplest solution would be to just make Center1 (the "Main" tank on the switch) a 174 gallon tank, empty the others and ignore them.

When I have a chance, I'll reinstall the stock system and see what I can come up with.  My best suggestion off the top of my head is just start from and drain the aux tanks first. then use the mains.

[jgf]

That's what I've been doing. 

 

It's a little less irritating if you enable aileron trim so can tweak that to account for fuel imbalance;  SimTech provided the control but never enabled it in the air file.