The Zero Fuel limit is determined to ensure that during the whole flight and at landing theaircraft CG remains within the limits.
3.9.2. Zero Fuel limit computation method
Two different methods are used to determine the Zero Fuel limit, depending on procedure applied on the balance chart.
a) Zero fuel limit takeoff protected :
. IF Zero fuel CG is within the Zero fuel limit . And IF takeoff weight and landing weight are compliant with the operational takeoff and landing maximum weights. THEN Takeoff, Landing and In Flight CG are within the allowed limits using the whole flight.
With this type of limit, assuming that the takeoff and landing weight limitations are checked on the AHM516 (Load Message) the only check to be performed on the balance chart is to ensure that the Zero Fuel CG position is within the Zero Fuel limit.
b) Zero fuel limit not takeoff protected :
. IF Zero fuel CG is within the Zero fuel limit . IF Takeoff CG is within the Takeoff operational limit . And IF takeoff weight and landing weight are compliant with the operational
takeoff and landing maximum weights. THEN Takeoff, Landing and In Flight CG are within the allowed limits using the whole flight.
With this type of limit, assuming that the takeoff and landing weight limitations are checked on the AHM516 (Load Message) the check to be performed on the balance chart is to ensure that the Zero Fuel and Takeoff CG position are within the Zero Fuel and Takeoff operational limits.
c) Computation method :
For each type of Zero Fuel limit the calculation principle is the same, it consists in :
.  Determining the possible aircraft CG position at Takeoff, Landing and Flight provided the Zero Fuel CG position is known, by analyzing the fuel vectors applicable to each flight phase. (refer to Fuel System Chapter).
.  Using the fuel vectors, determining all the allowed Zero Fuel CG positions so that all possible takeoff (for takeoff protected limit), landing and in flight CGs remains within their operational limits from no fuel to maximum fuel quantity.

C. BALANCE CHART DESIGN

3.9.3. Zero Fuel limit computation example : A320

The computation is based on the operational limits previously determined and on the possible CG positions at takeoff, landing and in flight for a given Zero Fuel CG position, these positions are given by the different fuel vectors.
For A320 family aircraft the takeoff, in flight and landing fuel vectors are identical.
a) Zero fuel limit takeoff protected :
Each flight phase fuel vector is leaned against the corresponding operational limit. In the case of A320 aircraft the fuel vector is leaned against the more inside operational limit.
This operation is repeated for Zero Fuel weights between minimum aircraft weight and Maximum Certified Zero Fuel Weight.
　
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