getting to grips with fuel economy(19)

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The different mach numbers all coalesce together and the FMGS line forms the common boundary. Climb speed increases from the left to the right. Least fuel is obtained using a 0.76/280 technique. Mach No has little influence, but increasing speed from 280 to 330kias decreases time by 6% and increases fuel by 6%. 

Completely different characteristics are also shown in the next chart (A340-642).

This shows a common technique is good for both fuel burn and time. The optimum is 320/0.80. There is little Mach No effect, but reducing the speed to 270 kias will increase fuel by 4% and time by 8%. Because the optimum technique is good for both fuel and time, there is a single FMGS point for all cost indeces.
Earlier versions of the A340 showed that some marginal time benefit could be gained by climbing faster. However this would have affected the flight levels achieved. Consequently there is no variation of FMGS climb speed with cost index  for all the A340 family.
Appendix A presents some examples of time - fuel charts for other Airbus aircraft. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5.2.4 CLIMB TECHNIQUE COMPARISON TABLES

 
 The following tables show, for various Airbus aircraft, the climb time and fuel variations for a fixed distance, to FL 350, relative to a 300kias reference speed. 
 
Effect of Climb Speed on Fuel
Aircraft
 Climb 
 .Fuel – kg
 
 
 Mach No.
 270KT
 280 KT
 300 KT
 320 KT
 330 KT
 
A300
 0.78
 +40
 +15
 0
 +5
 +10
 
A310
 0.79
 
 +5
 0
 +5
 +15
 
A318/A319/A320
 0.78
 
 -15
 0
 +30
 +70
 
A321
 0.78
 
 -10
 0
 +25
 +60
 
A330
 0.80
 +15
 +5
 0
 +20
 +35
 
A340–200
 0.78
 +45
 +20
 0
 +10
 +25
 
A340-300
 0.78
 +105
 +50
 0
 -5
 +20
 
A340-500/600
 0.82
 
 +135
　
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