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8. FCOM procedures require not less than a defined time before shutting down the other engine(s) after landing. On engines with a high bypass ratio, the cool-down time after reverse operation, prior to shut down has a significant effect on engine life.
9. If an operator decides to use one or two engine out taxi, then FCOM recommendations about which engine(s) to use should be followed.
As engine-out taxi requires more thrust per engine to taxi and maneuver, caution must be exercised to avoid excessive jet blast and FOD. More thrust is necessary for breakaways and 180 degrees turns.
On twin-engine aircraft slow and/or tight taxi turns in the direction of the operating engine may not be possible at high gross weight.
Single engine taxi may also be considered at low weights to avoid excessive use of the brakes to control the acceleration tendency with all engines. This brake use would be detrimental to carbon brake life.
The following table gives an indication of the advantages of engine out taxi for 8 of the 12 minutes total taxi time, leaving 4 minutes warm up time.
Fuel savings with Engine out taxi
Aircraft types
12 minutes taxi (all engines)
12 minutes taxi (8 with engine out)
Engine Out taxi savings
A300-600
300kg
200kg
100kg
A310
240kg
160kg
80kg
A318
120kg
80kg
40kg
A319
120kg
80kg
40kg
A320
138kg
92kg
46kg
A321
162kg
108kg
54kg
A330
300kg
200kg
100kg
A340-200/300
300kg
250kg
50kg
A340-500/600
420kg
350kg
70kg
For engine out or all engines taxi, the use of a slow taxi speed costs fuel and time. A burst of power should be used to get the aircraft to taxi speed, then the power should be reduced to idle. However 30kt should not be exceeded.
4.5 FUEL FOR TRANSPORTATION
The normal message regarding fuel burn is that it is more economical to carry the minimum amount required for the sector. However there are occasions when it is economic to carry more fuel. This is when the price of fuel at the destination airfield is significantly higher than the price at the departure airfield.
However, since the extra fuel on board leads to an increase in fuel consumption the breakeven point must be carefully determined.
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