Getting to Grips with Aircraft Weight and Balance(79)

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Landing gears retraction moves the aircraft CG forward so the real in flight CG will always be forward of the estimated value. So for forward certified CG operational margins determination the maximum forward movement has to be taken into account to prevent the aircraft CG being out of the limits. For the aft certified CG operational margins determination, there is no risk of being out of the limits as the operational configurations will always lead to a more forward CG than the estimated one. Nevertheless it is possible to take benefit of this situation by taking into account this CG movement is reducing the aft operational margin.

C. BALANCE CHART DESIGN
. ex : A330-200

Flaps and Slats movements : Takeoff configuration : the possible configurations are CONF 1+F, CONF 2, CONF 3. Impact on forward operational limit : Eaircraft CG movement = 0 kg.m or ECONF 1+F Impact on aft operational limit : Eaircraft CG movement = ECONF 3 = + 368 kg.m Landing configuration : the possible configurations are CONF 3, CONF FULL. Impact on forward operational limit : Eaircraft CG movement = 0 kg.m or ECONF 3 Impact on aft operational limit : Eaircraft CG movement = ECONF FULL = + 476 kg.m
Landing Gears movements : Flight configuration : Nose and Main landing gears retracted Impact on forward operational limit : Eaircraft CG movement = EMain + ENose = - 6677 kg.m Impact on aft operational limit : Eaircraft CG movement = 0 kg.m or EMain gear + ENose gear
WEIGHT AND
BALANCE
WEIGHT AND
BALANCE
C. BALANCE CHART DESIGN

3.6.2. Water movement from potable to waste tank

DOW and DOCG values are published for the following configuration :
. Water is located in the potable water
tanks. So on the balance chart all the aircraft CG values correspond to this configuration.
In reality at landing part of the water is located in the waste tanks and part of the water has been ejected out of the aircraft.
Eaircraft CG movement = Moment due to item movement = Moment due to water movement from potable tanks to waste tanks + Moment due to water ejection.

C. BALANCE CHART DESIGN

Eaircraft CG movement = WWater in waste tank x (H-armfinal position . H-arminitial location) + WWater ejected x (H-armfinal
position . H-arminitial location).
Eaircraft CG movement = WWater in waste tank (H-armwaste tank . H-armpotable water tank) - WWater ejected x H-armpotable
water tank.

Position of the different tanks in the aircraft are published in WBM 1.30
. ex : A330-200

..
.

..
.

..
.

Takeoff configuration 700 kg of water in the potable water tanks. Landing configuration :
..
.

-1/3 of the water ejected out of the aircraft,
-2/3 of the water in the waste tank.
Eaircraft CG movement = WWater in waste tank (H-armwaste tank . H-armpotable water tank) - WWater ejected x H-armpotable
water tank.
2 52.587 +
　
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