Modifying fuel tank #

[JBaymore]

Need som help here.  I've mucked about some stuff in aircraft.cfg files and custom done some things...... but FAR from an expert at it.  ;)

I am looking to make my BAe 146-200 that my simpit is modeled after a little more realistic.  The visual and flight model I am using is Jon Murchison's, and it is pretty darn nice as it sits.

But the real aircraft apparently has FOUR wing tanks plus the center tank and the normal configuration is that one wing tank typically feeds one engine unless commonfeeds / crossfeeds are set "on".   The Murchison model has only one wing tank on each wing.


Below is the [FUEL] seciton of the aircraft config file that exists:

---

fuel_type = 2
number_of_tank_selectors = 2
Center1 = 0, 0, 0, 2446, 0
LeftMain = -3, -19, 0, 315, 0
RightMain = -3, 19, 0, 315, 0
electric_pump=0

---

I know from looking at the [FUEL] section of the default Boring 747 that the following tanks are listed in that aircraft:

LeftAux, RightAux, LeftTip, RightTip, Center1, and Center2.

So I am guessing that I should be able to add the second fuel tank to each wing (or even a third) by specifying the appropriate factors such as position, total gallons, usable gallons, and so on.

Is this just a matter of altering the aircraft.cfg file .... or do I have to edit the ####.air file as well (never done that!)?

If I add the tanks in the aircraft.cfg file........ how do I get the fuel to "go" to the engines?  Will it automatically just "happen".......or just sit in the tanks untouched?  Can I assign a specific tank to an engine?  How do I assign a x feed for the added tank?  And so on.......

Any other thoughts you aircraft designers might have on this subject would also be appreciated.

best,

.......................john

[Gypsy_Baron]

-SNIP-
But the real aircraft apparently has FOUR wing tanks plus the center tank and the normal configuration is that one wing tank typically feeds one engine unless commonfeeds / crossfeeds are set "on".   The Murchison model has only one wing tank on each wing.


Below is the [FUEL] seciton of the aircraft config file that exists:

---

fuel_type = 2
number_of_tank_selectors = 2
Center1 = 0, 0, 0, 2446, 0
LeftMain = -3, -19, 0, 315, 0
RightMain = -3, 19, 0, 315, 0
electric_pump=0

---

I know from looking at the [FUEL] section of the default Boring 747 that the following tanks are listed in that aircraft:

LeftAux, RightAux, LeftTip, RightTip, Center1, and Center2.

So I am guessing that I should be able to add the second fuel tank to each wing (or even a third) by specifying the appropriate factors such as position, total gallons, usable gallons, and so on.

Is this just a matter of altering the aircraft.cfg file .... or do I have to edit the ####.air file as well (never done that!)?

I can offer a little help here. When I was creating my L-188 panel
I did some adding of fuel tanks successfully by simply changing the
aircraft.cfg file so the answer to your question is yes.

If I add the tanks in the aircraft.cfg file........ how do I get the fuel to "go" to the engines?  Will it automatically just "happen".......or just sit in the tanks untouched?  Can I assign a specific tank to an engine?  How do I assign a x feed for the added tank?  And so on.......
-SNIP-
.......................john

The fuel distribution in FS9 happens automatically unless you have
gauges programmed to intervene, as I recall. Fuell will be burned
from the outboard tanks first, then from those more inbo9ard, etc.
You CAN create gauges to force the engines to burn from a
specific tank(s) but the SDK isn't very helpfull in describing what
is necessary and it's not straight forward.
Again, when I did my L-188 panel I created a version that had
controls to switch tank/engine configurations but I had to re-name
certain tanks and change the fuel gauge code acordingly to make
it happen. It wasn't pretty but it did work.
My suggestion is "don't go there" until you're at the point where
you want to dabble in XML coding and beyond

 Paul

[JBaymore]

Gypsy_Baron,

Thanks for the reply.  It was a definite help.

I researched the aircraft a bit and found out the gallon capacity of the real BAe 146-200, and the number and general location of the tanks.  For the locations of the tanks... I just have general info....not exact placements.  So I had to sort of "guestimate" the tanks CG locations from the general wing geometry of the plane.  This is not really that good... but not sure how to solve that one otherwise.

The original Jon Murchison BAe model (which I love in every other way) has a very unrealistic set of fuel tank locations in the cfg file.  It is just about the opposite of the real aircraft; his has most of the fuel in the center tank(2446 gal.) ....and the real one has most of the fuel in the wings (2438 gal.).  Then there are also wing root aux. tanks of 310 gal.

I tried just changing the tank configuration in the cfg file.  At first it seemed to work OK.  The new tanks and volumes show up in the "fuel and payload" loading screen in the sim.  And they work.  And the fuel is being drawn from them.....currently is seems evenly from all.

However...... the aircraft's flight characteristics seem to have been dramatically changed.  It is not as "agile", feels like it is VERY heavy in a turn, and the autopilot on approach has trouble maintaing lateral allignment... it swings back and forth trying to follow the localizer beam.

So I am guessing that there are a LOT of other interrelated variables that I am now ALSO going to have to change here.  My guess is that moving the weight out to the wings from the center tank has changed the moment of intertia of the lever arm of the wings and other such stuff.  Crap.

Here is a section of my current aircraft.cfg file:

---

//--------------------------------------------
//added 4/16/04 by J. Baymore (more realistic fuel setup)
[fuel]
Center1=0.000, 0.000, 0.000, 661.000, 5.000
LeftMain=-3.000, -28.00, 0.000, 1219.000, 5.000
RightMain=-3.000, 28.00, 0.000, 1219.000, 5.000
LeftAux=-3.00, -7.00, 0.000, 155.000, 3.000 //root tanks
RightAux=-3.00, 7.00, 0.000, 155.000, 3.000 //root tanks
//--------------------------------------------

//ORIGINAL MURCHISON FUEL TANKS
//Center1=0.000, 0.000, 0.000, 2446.000, 0.000
//LeftMain=-3.000, -19.000, 0.000, 315.000, 0.000
//RightMain=-3.000, 19.000, 0.000, 315.000, 0.000

fuel_type=2.000
number_of_tank_selectors=2
electric_pump=0

---

One option I am considering is to just "overlap" the main wing tanks in the config file....... put their placements right on top of each other in the original Murchison "center tank" geometry location.  Then leave the center tank where it is too.  Unrealistic from a "physical accuracy" standpoint .....but his model's weight and balance was based mainly on this "center heavy" layout, I guess.  And then I might play with the small aux tanks location a bit.  Or maybe even put all the tanks in the center position....."on top " of each other.

Not sure if the "on top of each other" thing will work from the sim's point of view.


Once again.... any suggestions that anyone may have would be greatly appreciated.

best,

........................john

[Travis]

First off, the movement problems you mentioned are absolutely because of the reason you stated.  The wings are now heavier than before, meaning the gross weight has moved out over a larger area.  

Imagine holding two bricks in your hands.  Sit in a swivel chair and hold them close to your body.  You can swivel fairly easily back and forth without moving around too much.  The bricks aren't needing to move very far through space.

Now spread your arms wide.  NOW swivel the chair.  Harder, right?  The bricks haven't changed weight or mass, just moved farther from your COG, right?  Same thing with the tanks.

As for how to rectify this, I would suggest you go over to the FFDS forums and take a look at their sections.  They have a whole forum section dedicated to FDs.  I'm sure you'll be able to find an answer over there.

Moving the tanks into the center will indeed solve the problem, as the sim doesn't care where they are, as long as they are there.  You can put them in the cockpit, for all the difference it would make.

[JBaymore]

[quote]
Moving the tanks into the center will indeed solve the problem, as the sim doesn't care where they are, as long as they are there.