Getting to Grips with Aircraft Weight and Balance(96)

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During its operational life, the aircraft is going to be modified in different possible ways (new cabin arrangement, Service Bulletin implementation, new equipment…). These modifications are going to have an impact on the weight and the CG of the aircraft and therefore the aircraft as to be weighed on a regular basis. Moreover, the mass and the CG of each aircraft shall be re-established either by weighing or calculation (if the operator is able to provide the necessary justification to prove the validity of the method of calculation chosen), whenever:
. the cumulative changes to the dry operating mass exceed ± 0.5% of the maximum landing mass . or the cumulative change in CG position exceeds 0.5% of the mean aerodynamic chord.
2.1.2. Fleet mass and CG position:
The FAA and the JAA allow an operator that flies a fleet of the same type of aircraft (same model and configuration) to use an average dry operating weight and CG position for the whole fleet. However, individual aircraft weight and CG have to meet the following tolerances:
. The weighed or calculated weight of the aircraft varies by less than ±0.5% of the maximum structural landing weight from the established dry operating fleet mass. . The CG position varies by less than ±0.5% of the mean aerodynamic chord from the fleet CG.
If an aircraft does meet these tolerances, it has to be omitted from the fleet.
However, in the case where an aircraft falls within the tolerance for the dry operating weight but
is out of the CG range, it can still be operated with the fleet average mass but with an individual
CG position.

LOADING LOADING

A. LOADING GENERALITIES

. Fleet values determination:
The number of aircraft that have to be weighed varies with the number of aircraft in the operator‘s fleet. If ”n‘ is the number of aircraft in the fleet using fleet values, the operator must at least weigh, in the period between two fleet weight evaluations, a certain number of aircraft defined in the Table below:
Number of aircraft in the fleet  Minimum number of weighing 
Less than 3  n 
4 . 9  2 n + 3 
10 or more  10 n + 51 

The interval between two fleet mass evaluations must not exceed 48 months and the airplanes that have not been weighed for the longest time shall be weighed in priority.
2.1.3. Individual weights:
An aircraft that does not use fleet values must be weighed every 48 months.
2.2. Aircraft Weighing
The weighing of the aircraft can either be done on the aircraft‘s wheel or on jacks.
2.2.1. Defueling
The first action prior to aircraft weighing is the defueling of the aircraft. In order to do so, the aircraft‘s nose is lifted up to bring the aircraft to a zero degree pitch attitude. This is done with the help of the aircraft clinometer located in the refueling panel. Once this is done, defueling can be started. The information used is the information of the FQI. The defueling procedure prior to weighing can be found in the Weight and Balance Manual. When the fuel quantity indicated is equal to zero, this means that all the pumpaple fuel has been removed from the aircraft. Extra fuel can be removed using the water drain. Once this is done the only fuel left on board the aircraft is the undrainable fuel (for quantities, refer to the W&B Manual). Fire services have to be present during the operation and the aircraft must be earthed.
　
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