Getting to Grips with Aircraft Weight and Balance(58)

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a) Determination of the fuel distribution per tank after the refueling process
First it is necessary to know the fuel quantity in each tank depending on the total selected fuel on board. Thanks to the automatic refueling system, the fuel dispatch among the several tanks of the aircraft is automatic and leads always to the same fuel distribution in each tank for a given total fuel quantity and a given fuel density.
. Ex : WBM A330-200 refueling sequence
In WBM section 1.20.02 page 1, a graph (established at the standard fuel density of 0.785 kg/l) and a written procedure (irrespective of fuel density) summarize the refueling sequence: from a given total fuel quantity (in kg), the fuel quantity that will be dispatched by the automatic refueling system in each individual tank can be deduced.
For instance the automatic refueling procedure on A330-200 aircraft (equipped FCMS standard 7.0) is:
-
inner tanks refueled up to 3000kg per side (to fill in the collector cells)
-outer tanks refueled to full

-
inner tanks refueled up to total fuel equals 36500 kg

-trim tank refueled up to 2400 kg
-inner tank refueled to full
-trim tank and center tanks are simultaneously refueled up to full.

Total fuel qty = 60000 kg

C. BALANCE CHART DESIGN

In the above example, FOB = 60000 kg. It leads to the following fuel tank distribution (when the
fuel density is equal to 0.785 kg/l):
Inner (one side) : 25935 kg
Outer (one side) : 2865 kg corresponding to full outer (3650 liters) at the standard fuel density 0.785 kg/l
Trim : 2400 kg
As the automatic refueling sequence contains break points defined in volume (outer tanks are fueled to high level shut-off for instance), the corresponding fuel quantity in weight will depend on the fuel density. On the above example, if the density were 0.76 kg/l, then the outer weight would have been 2774 kg and so the inner weight would have been 26026 kg:
60000 .
(2774 ×
2 +
2400)
Inner_weight ==
26026 kg per side
2
Consequently, the fuel weight distribution per tank depends on the fuel density.
WEIGHT AND
BALANCE
WEIGHT AND
BALANCE
C. BALANCE CHART DESIGN

b) Determination of the fuel CG position per tank after the refueling process
Once the fuel weight distribution per individual tank is known, the fuel CG per tank can be deduced thanks to individual fuel tank table published in WBM section 1.20.03. To do so, we need to convert the fuel weight in each tank in term of volume per tank. In fact, the fuel CG position per tank depends on the fuel volume in it.
As a general fact, because to the fuel tanks shape the fuel CG in the tank depends on the actual fuel quantity in it. .That is why WBM individual fuel tank tables give the H-arm of the tank as a function of the fuel volume.
. Ex : WBM A330-200 Table of Fuel H-ARM Outer tanks
　
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