E cargo1index table + E cargo2 index table + E cargo3 index table + E cargo4 index table + E cargo5 index table
222Epassenger index tables =±
E cabin OA index table + E cabin OB index table + E cabin OC index table + K
C. BALANCE CHART DESIGN
3.5.2. Graphical balance chart inaccuracy
On the graphical balance chart the .index value for each item loaded is read on a diagram.
On this diagram the .index is drawn manually on each line for each item loaded.
The manual drawing generates an inaccuracy due to the drawing precision as illustrated below :
the blue line being the ideal drawing and the red line a manual drawing.
The inaccuracy due to this manual input is highly dependant on the index scale readability on the balance chart and the index scale is linked to the choice of index formula C constant. AIRBUS standard constants are determined in order to have a major step in index length drawn on the chart between 1 and 1.5 cm, each major step is divided into 10 minor steps so one minor step length is between 1 and 1.5 mm. Then the cargo weight steps and passenger number steps on the diagram are determined so that between two oblique lines on the scale there is no more than 5mm to ensure sufficient accuracy when interpolating.
Following these design rules it is assumed that on each scale the maximum inaccuracy is of 0.5 index unit. The inaccuracy due to one scale is independent from the inaccuracies due to the other scales so :
2222 2
Ecargo index tables =±
E cargo1index table + E cargo2 index table + E cargo3 index table + E cargo4 index table + E cargo5 index table
222Epassenger index tables =±
E cabin OA index table + E cabin OB index table + E cabin OC index table + K
WEIGHT AND
BALANCE
WEIGHT AND
BALANCE
C. BALANCE CHART DESIGN
3.5.3. example on A330 graphical balance chart
On this balance chart the final CG is determined . entering the Dry Operating Index in the initial scale. . determining .index for each cargo compartment (5 scales) . determining .index for each cabin section (3 scales)
. determining the fuel .index in the fuel index table (inaccuracy depends on the weight step in the table, and on the procedure interpolation/no interpolation) in this example inaccuracy = 2 index units.
. entering the fuel index in the fuel scale
Each inaccuracy scale is independent from the other ones.
222 22
E =±
E inital scale + 5 ×
E Cargo scale + 3 ×
E Cabin section
scale + E fuel table + E fuel scale
CG determination method 2 2 222 22
E =±
0.5 +
5 ×
0.5 +
3 ×
0.5 +
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