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,

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

Quote:


Locke,

Thanks for the feedback.  

The general angular momentum / inertia stuff I understand..... just not exactly how to apply it in flight sim applications.  Didn't know that stuff could co-exist in space though.  Thanks.  And I really do not want to get into a massive pile of math to recalculate something that already worked OK to start with.  I have my hands full with the physical simpit project itself.  Up to my ears in Phidgets and another Hagstrom KE-72 on the ND machine.

So.... I moved the center tank, and two main wing tanks locations to co-exist at 0,0,0,, and put the small aux tanks in the original wing position.   Mentally this seems incorrect........ but that was just about the way the model was designed, I guess.  And having three objects in the "same place" seems like a contradiction in physical laws   ??? .  

The new wing tanks are now about half the size of the original ones in gallons.... so the aircarft got a tad more "nimble" in a turn.  But at least it doesent feel like an overloaded 747 with hydraulic problems anymore.  

Maybe I will try shifting the CG of the two large wing tanks a tad to the lateral sides of the 0,0,0 point to make up for the current lighter loading at the +19, -19 points.  I think I might pick up Aircraft COntainer Manager to make this a bit easier.  Then I can just match up the aircarft CGs by moving the tanks to match the original cfg file.

best,

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

PS:  Actually in the cockpit would make her go nose heavy.