getting to grips with fuel economy(16)

 
This effect is very dependent on the variables mentioned in the introduction, plus the choice of VR and V2. However the trend is always the same , with high flap/slat configurations (more extended) using more fuel than the lowest setting. Typical penalties/takeoff of higher flap settings compared with the low  flap settings Conf 1+F are shown below  (note that for the A300/A310 Conf 1+F, Conf 2 and Conf 3 corresponds to the Flap 0,15 and 20 configuration respectively).
Aircraft
 Conf 2
 Conf 3
 
A300/A310
 1- 5kg
 15kg
 
A320
 3-5kg
 8-13kg
 
A330
 12kg
 24kg
 
A340
 30kg
 50kg
 

 
These figures assume Full take-off thrust. The advantage of Conf 1+F increase with reduced power take-offs.
5.1.4 SPEEDS

During a non limiting full power take-off, the use of the higher speeds appropriate to flex thrust instead of optimized speeds appropriate to the actual temperature can reduce the fuel burn by up to 8kg.
5.1.5 FLEX THRUST

Compared to a full thrust take-off, flex thrust will generally increase fuel burn. The increased time at low level offsets the slight reduction in fuel flow induced by the lower thrust. Typical increases  are as follows:
 
Aircraft
 Conf 1+F
 Conf 2
 Conf 3
 
A300/A310
 10kg
 10kg
 10kg
 
A320
 1kg
 5kg
 5kg
 
A330
 0
 0
 0
 
A340
 5kg
 20kg
 25kg
 

 
5.1.6 NOISE FLIGHT PATHS

The effect of an ICAO type A noise flight path, with climb thrust selected at 800ft and clean up delayed until 3000ft is generally to increase fuel burn compared to the standard take-off with power reduced at 1500ft. The actual distance to a fixed height, say 5000ft, varies very little with configuration. The main effect is the different altitude – speed history experienced by the engines.  Typical values are as follows:
 
Aircraft
 Conf 1+F
 Conf 2
 Conf 3
 
A320
 -4kg
 +5kg
 +2kg
 
A330
 +100kg
 +100kg
 +115kg
 
A340
 +90kg
 +130kg
 +125kg
 

 
 
5.1.7 COURSE REVERSAL

In the event that a course reversal is required after take-off, then much distance can be saved using a lower initial climb speed. Suppose ATC require an aircraft to maintain runway heading to 6000ft. A lower climb speed will achieve this altitude earlier and thus reduce the ground distance and fuel burnt.
　
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