Getting to Grips with Aircraft Weight and Balance(42)

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For the A300-600, A310, A330 and A340 types, the further aft the CG, the more significant the fuel savings. Furthermore, when flying above FL350, at a high weight, the decrease or increase in fuel consumption according to the reference is significant. Thus, loading is very important especially for high weights and for aircraft which have no automatic center of gravity management: we notice that, for high weights and FL above 350, the specific range variation can reach 2%.
Contrary to the other aircraft, specific range variations with respect to the CG position are random for the whole A320 family. This is due to a complex interaction of several aerodynamic effects. Whatever the influence of the CG position on specific range, it is negligible The single aisle aircraft are not equipped with in-flight fuel transfer systems, they are not fitted with a trim tank.
WEIGHT AND
BALANCE
WEIGHT AND
BALANCE
A. GENERALITIES

d) Example
On a 1000 NM stage length, the increases in fuel consumption when the center of gravity position is 20% with regards to the fuel consumption when the center of gravity position is 35% are summed up in the following table for an aircraft with a high weight and at a high flight level.
A300-600/A310
2.5

2
1.5 1
0.5 0 -0.5 -1
-1.5 -2
SR variation (%)
A340

Flight Level
Fuel increment (Kg)/1000Nm between a 20% CG and a 35% CG 
A319/A320/A321  Negligible 
A330  220 
A340  380 
A310  250 
A300-600  230 

A. GENERALITIES
3.4. Impact on landing performance
3.4.1. Landing distance or landing weight
The aircraft operating speeds are referenced to the stalling speed. At landing: VApp ≥1.3Vs (1.23Vs1g )
Now, the Vapp value directly impacts the landing distance (or the landing weight).
Vs

V

LD
app

So for a given Landing Distance: the lower the stall speed (Vs) value, the greater landing weight (LW).
Reminder: Forward CG position . High stall speed Aft CG position . Low stall speed.
The further aft the CG, the smaller the LD (the greater the LW).
3.4.2. Basic and alternate CG positions
As for takeoff performances, when determining the aircraft landing performance (LW, LD), the
calculation is always performed at the most forward-certified CG position. Therefore, for aircraft
having a naturally aft CG position (tail heavy aircraft), everyday operations might be penalized
using this very forward value.

Only the A320 has two different certified CG. For the other aircraft, the position of the CG is of no
influence on landing performances as long as it stays within the certified limits.
The important performance as far as landing is concerned is the landing distance. As noted in
the FCOM of the A320, a correction has to be made in the case of an alternate CG.
　
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