Applicable to: ALL
The selected cruise altitude should normally be as close to optimum as possible. As deviation from optimum cruise altitude increases, performance economy decreases. The following table provide average specific range penalty when not flying at optimum altitude.
FUEL MONITORING
Applicable to: ALL
11 The flight plan fuel burn from departure to destination is based on certain assumed conditions. These include gross weight, cruise altitude, route of flight, temperature, cruise wind and cruise speed. Actual fuel consumption should be compared with the flight plan fuel consumption at least once every 30 min.
NORMAL OPERATIONS
CRUISE
A318/A319/A320/A321
FLIGHT CREW TRAINING MANUAL
The crew should be aware that many factors influence fuel consumption, such as actual flight level, cruise speed and unexpected meteorological conditions. These parameters should normally be reflected in the FMS.
The crew may suspect a fuel leak in case of :
? A significant deviation between planned and actual fuel figures
? An excessive fuel flow leading to a potential imbalance
? An abnormal decrease in total fuel quantity (FOB+FU)
In this situation the crew must apply the FUEL LEAK paper procedure.
FUEL TEMPERATURE
Applicable to: ALL
Fuel freeze refers to the formation of wax crystals suspended in the fuel, which can accumulate when fuel temperature is below the freeze point (-47 °C for jet A1) and can prevent proper fuel feed to the engines.
During normal operations, fuel temperature rarely decreases to the point that it becomes limiting. However, extended cruise operations increase the potential for fuel temperatures to reach the freeze point. Fuel temperature will slowly reduce towards TAT. The rate of cooling of fuel can be expected to be in the order of 3 °C per hour with a maximum of 12 °C per hour in the most extreme conditions.
If fuel temperature approaches the minimum allowed, the ECAM outputs a caution. Consideration should be given to achieving a higher TAT:
? Descending or diverting to a warmer air mass may be considered. Below the tropopause, a 4 000 ft descent gives a 7 °C increase in TAT. In severe cases, a descent to as low as 25 000 ft may be required.
? Increasing Mach number will also increase TAT. An increase of M 0.01 produces approximately 0.7 °C increase in TAT.
In either case, up to 1 h may be required for fuel temperature to stabilise. The crew should consider the fuel penalty associated with either of these actions.
APPROACH PREPARATION
Applicable to: ALL
The latest destination weather should be obtained approximately 15 min prior to descent and the FMGS programmed for the descent and arrival. During FMGS programming, the PF will be head down, so it is important that the PNF does not become involved in any tasks other than flying the aircraft. The fuel predictions will be accurate if the F-PLN is correctly entered in terms of arrival, go-around and alternate routing.
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