getting to grips with fuel economy(20)

 
Effect of Climb Speed on Time
Aircraft
 Climb 
 .Time – minutes
 
 
 Mach No.
 270KT
 280 KT
 300 KT
 320 KT
 330 KT
 
A300
 0.78
 +0.8
 +0.5
 0
 -0.3
 -0.4
 
A310
 0.79
 
 +0.5
 0
 -0.5
 -0.6
 
A318/A319/A320
 0.78
 
 +0.5
 0
 -0.4
 -0.8
 
A321
 0.78
 
 +0.8
 0
 -0.6
 -1.0
 
A330
 0.80
 +0.9
 +0.6
 0
 -0.4
 -0.7
 
A340–200
 0.78
 +1.4
 +0.8
 0
 -0.6
 -0.8
 
A340-300
 0.78
 +1.5
 +0.9
 0
 -0.6
 -1.0
 
A340-500/600
 0.82
 
 +0.8
 0
 -0.6
 -0.8
 

 
It can be seen from the tables how the optimum techniques are very dependant on the aircraft type, and that a 10kt climb speed change can have a significant impact.
5.2.5 DERATED CLIMB

 
In order to reduce engine maintenance costs, there are derated climb options available on the A330 and A340 aircraft. There are two levels of derate, D1 and D2. At a certain altitude the derate is washed out such that at Max Climb rating is achieved generally before 30000ft. The following shows a typical derate thrust variation picture, but this will vary with engine and temperature.

 
However this derate will result in more fuel and time required to reach the same distance. The effect is dependant on aircraft weight, temperature and cruise flight level. The following table gives some typical penalties in ISA conditions to 35000ft.
 
 
 Derate D1
 Derate D2
 
Aircraft
 Weight (kg)
 Fuel Increase
 Time Increase 
 Fuel Increase
 Time Increase
 
A330-203
 190000
 5kg
 0.5 min
 20kg
 0.6 min
 
A330-223
 190000
 20kg
 0.2 min
 40kg
 0.5 min
 
A330-343
 190000
 20kg
 0.2 min
 35kg
 0.5 min
 
A340-212
　
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