E Innertanksfwd+E Outertanksfwd+E Centertankfwd+... 22 2
Efuel weight aft =+
E Innertankaft+E Outertankaft+E Centertankaft+...
C. BALANCE CHART DESIGN
c) Total fuel inaccuracy
The final fuel allowance includes the three above mentioned inaccuracies:
. Fuel weight inaccuracy linked to FQI inaccuracy (all flight phases)
. Inaccuracy on the fuel .index determination. (takeoff phase)
. Inaccuracy on the Zero fuel limit design (flight and landing phase only in case of
non takeoff protected Zero Fuel limit and on all three phases in case of takeoff
protected Zero Fuel limit)
Then the total inaccuracy is determined considering each inaccuracy independent from the other ones.
WEIGHT AND
BALANCE
WEIGHT AND
BALANCE
C. BALANCE CHART DESIGN
3.5. Inaccuracy due to CG computation method
The balance chart used to determine the aircraft CG position can be : . graphical . tabulated . computerized
In each case the computation is based on
. a sum of weights = DOW + Payload Weight +Fuel Weight
. a sum of index = DOI + Payload .Index +Fuel .Index
Each weight of the sum is rounded to the closest unit value.
Each index and .index of the sum may be rounded to :
. the closest index unit in the case of paper systems (graphical or tabulated)
. the closest decimal (tenth or hundredth) in the case of computerized systems.
The weight sum is then considered to be precise and no inaccuracy is taken into account. Depending of the rounding system of the index and on the method to determine the index value for each weight value, an index inaccuracy has to be taken into account.
Note1 : the computerized systems rounded to the tenth or hundredth, are considered usually to be precise enough not to take into account any inaccuracy. Note2 : some computerized systems may be based directly on each item H-arm value and not on the item .index, in this case the computation is usually much more precise (without pre-computation) and no inaccuracy is considered.
The index inaccuracy is first determined analyzing the balance chart as a number of index units. The value of the inaccuracy in term of moment depends on the index formula chosen.
C. BALANCE CHART DESIGN
3.5.1. Tabulated balance chart inaccuracy
On the tabulated balance chart the .index value for each item loaded is read in an index table.
There are two methods to define index tables : . Tables with constant step in index . Tables with constant step in weight.
a) Tables with constant step in index
Those tables are usually used for passengers and cargo .index for fuel .index tables with constant step in weight are used.
CARGO n
.index
203
+1
611
+2
1018
+3
1426
+4
1833
+5
