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characteristics because of the lower fixed speeds used in each configuration.
Each configuration shows very similar fuel flow, whichever speed technique is
used. The clean configuration green dot speed still represents the best single
choice for lowest fuel burn over the normal holding weight range.
The A330, which has the same hold speed schedules shows the same
characteristics, with clean configuration at green dot speed being marginally
better than clean configuration at 210kt over the normal holding weight range.
The A320 family shows a completely different set of characteristics as shown
in the graph on the next page.
Effect of Holding Technique on Fuel Flow
A310-324 ISA F/L 100
2500
3000
3500
4000
4500
5000
90 95 100 105 110 115 120 125 130
Aircraft Weight - tonnes
Fuel Flow - kg/h
Clean Green Dot
Clean 210kt
15/0 'S' Speed
15/0 170kt
Getting to grips with Fuel Economy IN FLIGHT PROCEDURES
- 65 -
The variation of different techniques is very weight sensitive. However it is
still the clean configuration at green dot speed that gives the lowest fuel flow. This
picture is typical of all the A320 family.
Finally the A340-500/600 has another set of configuration/speed
combinations and the following graph shows its different characteristics, but the
basic concept that the clean configuration and green dot is the best combination
still remains true.
Effect of Holding Technique on Fuel Flow
A320-214 ISA F/L 100
1400
1600
1800
2000
2200
2400
2600
2800
40 45 50 55 60 65 70
Aircraft Weight - tonnes
Fuel Flow - kg/h
Clean Green Dot
Clean 210kt
Conf 1 'S' Speed
Conf 1 170kt
Effect of Holding Technique on Fuel Flow
A340-642 ISA F/L 100
5500
6000
6500
7000
7500
8000
8500
9000
9500
10000
200 220 240 260 280
Aircraft Weight - tonnes
Fuel Flow - kg/h
Clean Green Dot
Conf 1 240kt
Conf 1 'S' Speed
Conf 2 210kt
5 - IN FLIGHT PROCEDURES Getting to grips with Fuel Economy
- 66 -
There is also altitude to be considered, although it is often not the
operator’s decision what flight level to hold at. Altitude has different effects on the
fuel flow, depending on the airframe/engine combination. However, whatever the
altitude effect, it generally affects all techniques equally; generally the higher the
hold altitude the lower the fuel flow. This however is true only up to a certain
altitude and this varies with each type.
The following table shows this altitude effect for a hold in the clean
configuration at green dot speed. The holding fuel flow is compared with the
lowest for the flight levels considered for each type, and the difference expressed
as a percentage.
Flight Level 50 100 150 200 250 300 350 400
A300B4-605R 4 2 1 0 3 8 16
A310-324 11 5 2 0 0 5 9 23
A318-111 13 8 4 2 1 0 0 5
A319-112 19 11 3 1 0 1 0 4
A320-214 13 5 3 1 1 1 0 2
A320-232 7 5 5 5 2 0 4 11
A321-211 14 11 8 3 0 1 5
A330-203 2 1 0 0 2 4 8 18
A330-223 9 9 5 2 0 1 6 14
A340-343 10 5 1 0 0 2 7 16
A340-212 3 2 0 0 2 3 5
A340-313E 2 1 0 0 2 3 5
A340-642 6 2 0 1 2 3 4 11
In order to allow an assessment of the sensitivity of each aircraft type to
different hold techniques, the following table shows the extra fuel required to
hold for 15 minutes at 10000ft in the first flap configuration at ‘S’ speed,
compared to Conf clean at green dot speed.
Getting to grips with Fuel Economy IN FLIGHT PROCEDURES
- 67 -
Effect of Holding in First flap Setting at ‘S’ speed compared with Clean at Green Dot speed
Aircraft types
Fuel Increase (kg)
Low Holding
Weight
Fuel Increase (kg)
High Holding
Weight
A300B4-605R 70 110
A300B4-622R 110 190
A310-324 70 135
A318 5 10
A319 10 30
A320 10 30
A321 30 50
A330-203 135 175
A330-223 175 205
A330-343 145 175
A340-212 170 230
A340-313 125 175
A340-642 130 150
The table shows that the green dot speed/clean configuration combination
enables significant savings to be made.
However, green dot speed increases with weight and can become higher
than the maximum recommended speeds, which are listed below:
Levels ICAO PAN-OPS FAA France
Up to 6,000 ft inclusive 230 KT 210 KT 200 KT 220 KT
Above 6,000 ft to 14,000 ft inclusive 230 KT 230 KT 230 KT 220 KT
Above 14,000 ft to 20,000 ft inclusive 240 KT 240 KT 265 KT 240 KT
Above 20,000 ft to 24,000 ft inclusive 265 KT 240 KT 265 KT 240 KT
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