3.3.2. Effect on the final aircraft CG position
The inaccuracy on the aircraft initial CG position will generate an inaccuracy on the final CG
position (ZFCG or TOCG) which can be determined in term of moment (EDOCG)
EDOCG = Real Aircraft Moment . Assumed Aircraft Moment
EDOCG = DOWreal x (H-armreal . H25) . DOWassumed x (H-armassumed . H25)
In the following we consider that DOWreal ≈ DOWassumed so
EDOCG = DOWassumed x (H-armreal . H25) . DOWassumed x (H-armassumed . H25)
EDOCG = DOWassumed x (H-armreal . H-armassumed)
As per regulation (H-armreal . H-armassumed) cannot exceed ±0.5% of the Reference Chord length.
± 0.5 × Length
Reference Chord
E = DOW ×
DOCG assumed
100
Note : the effect value depends on the DOWassumed so each time the DOW has to be changed the effect needs to be recalculated and so the total effect on the aircraft CG determine shall be modified also. In order to avoid continuous balance documentation modification, the operator can take a weight value of (DOWassumed + margin) including the possible weight modifications.
± 0.5 × Length
Reference Chord
E =(DOW + margin)×
DOCG assumed
100
. Ex: A320 in the following configuration:
MLW = 64 500 kg,
DOW = 39 400 kg
RC = 4.1935 m
0.5 × 4.1935
EDOCG =(39400 + 4000)× =±910m.kg
100
WEIGHT AND
BALANCE
WEIGHT AND
BALANCE
C. BALANCE CHART DESIGN
3.4. Inaccuracy on items loading on board the aircraft (passengers, cargo, fuel)
Any item loaded onboard the aircraft has a given weight and location. Nevertheless, this weight and/or CG position might not be known with enough precision. So there is an inaccuracy in the determination of the delta index due to the item loading which is due to an inaccuracy on either the item weight or on the item location.
In the following paragraphs the method to determine the effect of each inaccuracy is developed.
Note : Effects are supposed to be independent : location is supposed to be accurately known to calculate the effect of the error in weight, and the weight is supposed to be accurately known to determine the effect of the error on location.
. Inaccuracy on the item location
The inaccuracy on the item position generates an inaccuracy on the final aircraft CG position that can be determined in terms of moment (Eitem location).
Note : the item weight is considered to be accurately known.
Eitem location = Real Aircraft Moment . Assumed Aircraft Moment
Eitem location = (Aircraft Moment + Real Item Moment) . (Aircraft Moment + Assumed Item Moment)
Eitem location = Real Item Moment . Assumed Item Moment
Eitem location = Witem x (H-armitem real . H-armref) . Witem x (H-armitem assumed . H-armref)
Eitem location = Witem x (H-armitem real – H-armitem assumed) 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：Getting to Grips with Aircraft Weight and Balance(63)
