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FS2004 Refuelling nightmare

vololiberista

vololiberista

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1,468
Country
italy
I'm having serious problems matching a fuel dump/uplift gauge with the aircraft gauges.
The aircraft uses metre cubed and kilos whereas the fuel gauge uses US gallons converted. It seems each time there is a conversion a little bit is lost which accumulates to a gross error.
My on board gauges differ by 1000 kgs when full.
My current adjustment is
(A:FUEL LEFT QUANTITY, meter cubed) 802.84 * 21.4286 100 / * 1.015191 *
I added 1.015191 * to multiply up to the fuel dump/uplift figure but it doesn't seem to work.
Obviously there will be small discrepancies of a 100kgs or so but the error at the moment is 1,000kgs which is too much!
 
A:FUEL LEFT QUANTITY, meter cubed) 802.84 * 21.4286 100 / * 1.015191 *
Ok the A:FUEL LEFT QUANTITY, meter cubed) 802.84 * converts to kilos.
The 21.4286 100 / represents one tank ie. 21.4% of the whole is a small wing tank.
the 1.015191 * is to try to match the upload figure. It's this that doesn't work.
 
Ok i understand. have you tried:

(A:FUEL LEFT QUANTITY, meter cubed) 802.84 * 21.4286 100.0 / * 1.015191 *

should not make any difference.

Have you tried to make a fake gauge (sdk fuel pressure ) to only shows the value?
 
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The problem is that I'm in effect matching the variables in the uplift gauge with the fuel panel gauges.
They are now essentially in line. But in doing so the uplift now stops short of full.
The dials all have scales that are higher than the maximum. That's normal. but now as said the
uplift stops well short. For example an outer wing tank that has a gauge with a scale of 6,000.
Before the uplift stopped at 5,750 or thereabouts. Now with these adjustments it stops at around
5,300. It's curious. I might have to increase the tank capacity in the cfg file.
I think part of the problem at least is in the fact that the sim, the fuel dump gauge, FSUIPC and the dials all calculate
different values. It is a real pain to get US gallons to kilos consistently.
 
I am willing to review parts of the code if you like. fresh set of eyes.
 
Just a suggestion, maybe make your entire system in US gallons first to make sure everything is working correctly then convert back to kilos.:idea:
 
delivery guy said:
Just a suggestion, maybe make your entire system in US gallons first to make sure everything is working correctly then convert back to kilos.:idea:
Click to expand...
I considered that. But that would mean a complete rewrite from the ground up which I would like to avoid if possible.
Those simmers that just put a number into their FMC don't know how lucky they are!
I'm having to model the physical process by selecting required values on steam gauges under the wing. The fuel uplift automatically shutting off when the pointers match and then checking the EO's panel.
So I have eight separate gauges, plus the "bowser" gauge plus the EO's gauges. As you can see there are eight tanks, but the model only has four. Two of which are subdivided. Also the fuel dump/uplift gauge refuses to read TANK CENTER2 which means I have had to fudge that. And that is also part of my problem I think because ostensibly there is more fuel available. Having said that the upload amount seems a lot less now than it was which is strange.
ronh said:
I am willing to review parts of the code if you like. fresh set of eyes.
Click to expand...
What I'm going to do is to go back to square one as it were. Because now I'm getting lost in a quagmire of code. I'll send you those later so that you can see the discrepancy. What is odd is that it all starts off ok i.e. the tanks initiate with 11,000kgs. and all the gauges reflect their share being 15% of the total. It all goes wrong during the uplift.
underwing.jpg
 
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FSX gives A:FUEL WEIGHT PER GALLON as fuel weight per gallon in pounds

It it possible that your conversion of 802.84 may not consistent - just a thought?
 
What I've decided to do is to put all of (A:FUEL TANK CENTER QUANTITY, meter cubed) (A:FUEL TANK CENTER2 QUANTITY, meter cubed) + (A:FUEL LEFT QUANTITY, meter cubed) + (A:FUEL RIGHT QUANTITY, meter cubed) + 802.84 * into an L var. That way the uplift can go ahead unmolested so to speak. Also playing with an L var means that the gauge needle will show the correct value and stop short of the maximum sahown on the gauge which is akin to having a speedometer with 160mph but the car never able to attain that speed.
mgh said:
FSX gives A:FUEL WEIGHT PER GALLON as fuel weight per gallon in pounds

It it possible that your conversion of 802.84 may not consistent - just a thought?
Click to expand...
802.84 is a direct conversion from meter cubed to kilos so it is correct!
 
mgh said:
There isn't a direct conversion from cubic metres to kilograms - it depends on the density of the fuel. For example, Jet A1 Kerosine has a density between 775 - 840 kg/cube metre. That's quite a spread on your value of 802.84 kg/cubic metre.

http://www.exxonmobil.com/AviationGlobal/Files/WorldJetFuelSpecifications2005.pdf
Click to expand...
Yes I know about the density and temperature. In order to simulate though one would be calculating until the cows came home. So you can see 802.84 is a mean value.
 
ronh said:
Not sure if this will help. have you seen this thread. There seems to be a few issues with getting fuel tank settings properly set up.

http://www.fsdeveloper.com/forum/threads/fuel-question.61911/
Click to expand...
In actual fact there is quite a wide range of calculations if you look!
The fuel dump/uplift gauge actually converts from US gallons to litres then to pounds and then to kilos. So it overstates the actual uplift total by 2-4 hundred for a full tank load. Having said that it does deposit the correct amount into the tanks. I've tried to fiddle with that but I'm tempted to leave alone and use the value on the EO's panel.
It would have been nice if MS had allowed the option to set up the fuel with different values instead of forcing everyone to use US gallons.
 
What exactly am I supposed to translate?

And does 6.7803 lb/gall agree with A:FUEL WEIGHT PER GALLON in pound/gallon or not?
 
From my second post - always get the units.

.80284 * 3.78541 = 3.0390785644

S.G. x liters/us gal => kg/us gal at a certain specific gravity jet fuel

1 cu. m = 1000 liters

.80284 kg/liter times liters/us gal ------ liters cancels out you get kg/us gal = 3.04 close enough to 3.0 from second post.

So to go from us gal to kgs for jet fuel => us gal x 3.04 = kgs

from the google:

There is NO standard conversion factor between Litres and Kilograms for Jet A1. It all depends on the specific gravity (SG) for the day.

We had fueling charts written in steps of 0.005Kg/L for S.G's from 0.760 - 0.840 Kg/L. In reality, the range is usually between 0.780 - 0.810 Kg/L, and we are supplied with (on a daily basis) and expected to use an S.G. that is accurate to 0.001 Kg/L.

A ROUGH rule of thumb to see if you are in the ballpark is to use an S.G of 0.800 Kg/L, but this may carry an error of up to 5% in cases where the actual S.G. is nearer the extremes of 0.760 or 0.840 Kg/L.

Whilst all the above comments are good for super accurate conversions, if you want a ball park figure to check that the tanker driver hasn't fiddled the figures to charge for more than he's put in, then 1800lbs = 1000ltrs. Also 1000lbs = 150USG. Easy eh?

my edit

150 us gal = 450 kgs = 1000 lbs

from the above posts 11000 kgs total fuel?

11000/3.04 = 13681 liters = 13.681 cu m - are you starting out with this much acuracy in the cu m?
 
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Actually fuel data is -or should be- something rather simple to manage, considering FS provides accurate conversions and there are simple formulas for those equivalencies FS does not contemplate.

Are you using Doug's fuel dump gauge? I don't have a real clue on what are the figures your fuel gauges and the dump/uplift gauge display (or need to display) but I guess it would be the best to use (A: Fuel Tank n Quantity,gallons) vars multiplied by (A:fuel weight per gallon,pounds); saved into (L:Tank n Quantity,pounds) and expressed as (L:Tank n Quantity,kilograms)

Tom
 
ronh said:
A ROUGH rule of thumb to see if you are in the ballpark is to use an S.G of 0.800 Kg/L, but this may carry an error of up to 5% in cases where the actual S.G. is nearer the extremes of 0.760 or 0.840 Kg/L.
Click to expand...

The OP has a discrepancy of 1.015191 - that's 1.5%, not 5%
 
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