In-Flight Fuel Management

In-Flight Fuel Management

Minimum Required Fuel on Board

At Brake Release

The Commander shall ensure that following fuel quantities are on the board at brake release (i.e. start of take-off roll):

• Trip fuel;
• Contingency fuel;
• Alternate fuel and/or additional fuel;
• Final reserve fuel.

Accordingly, during taxi, only the taxi fuel and extra fuel may be burned at Commander's discretion.

Anytime In-flight

The following fuel quantities must be available on board:

• Trip Fuel for the remaining portion of flight;
• Alternate Fuel;
• Final Reserve Fuel;
• Additional fuel (if required).

Whenever the flight crew foresees a shortage of fuel in-flight that might affect the safe conduct of the remaining portion of the flight, flight plan changes should be initiated as soon as practicable to take the necessary precautions to avoid a change of destination.

If, as a result of an in-flight fuel check, the expected fuel at the destination aerodrome will be less than the required alternate plus final reserve fuel, the Commander must decide whether to continue to the destination or to divert to another suitable aerodrome. His decision shall be based on the evaluation of all significant factors at the destination, along with the diversion route and the alternate aerodrome, e.g.:

• The meteorological conditions at destination and alternate at decision time and ETA;
• The number and state of suitable runways at destination and alternate and approach aids available;
• The EAT issued or anticipated;
• To land with not less than final reserve fuel.

At Decision Point

If the Decision Point Fuel Calculation procedure is used for pre-flight planning the Commander shall ensure that following fuel quantities are available at the enroute decision point:

• Trip fuel to the destination aerodrome; and
• Contingency fuel of not less than 5% of the estimated fuel used from the decision point to the destination aerodrome; and
• Alternate fuel if a destination alternate is required or additional fuel (15 min holding 1500 ft above destination aerodrome) if destination alternate is not required; and
• Final reserve fuel.

If the quantity is found to be less than above, a diversion to the en-route alternate shall be initiated unless safety reasons dictate another course of action.

At Reclearance Point

When in-flight replanning is performed (i.e. in-flight change of the destination aerodrome) the OFP must be amended accordingly. The Commander must ensure that the usable fuel on board at the re-clearance point is not less than the sum of:

a) Replanning to a destination for which a destination alternate is required:

• Trip fuel to the new destination; and
• Contingency fuel of not less than 5% of the estimated fuel used from the reclearance point to the new destination aerodrome; and
• Alternate fuel; and
• Final reserve fuel.

b) Replanning to a destination for which a destination alternate is not required:

• Trip fuel to the new destination; and
• Contingency fuel of not less than 5% of the estimated fuel used from the reclearance point to the new destination aerodrome; and
• Additional fuel (15 min holding 1500 ft above destination aerodrome); and
• Final reserve fuel.

At Point of Last Possible Diversion while Flying to an Isolated Destination

When approaching the last possible point of diversion to an available en-route aerodrome, a fuel check must indicate that the fuel remaining overhead isolated destination will not be less than the fuel required to hold for 2 hours. In the opposite case, the Commander must divert to a suitable en-route alternate. He may continue to the planned isolated destination only if it has two separate available runways and the weather conditions expected on arrival satisfy the planned approach requirements for either runway.

Fuel Situation Monitoring and Recording

The fuel situation shall be continually monitored by the flight crew. Changes in the operational status of destination aerodrome and of alternate aerodromes and deviations from the original flight plan must be taken into account.

Fuel checks shall be performed and recorded on OFP:

• Before engine start;
• Before start of take-off roll in case of prolonged taxi time, if applicable;
• At least at top of climb on short flights and every 30 minutes when in cruise;
• At specific fuel planning waypoints, if applicable (e.g. Point of no Return, Decision Point, Reclearance Point, etc.);
• After engine shut down.

The main purpose of the fuel checks is to:

• Compare actual fuel consumption with planned fuel consumption;
• Detect a possible fuel leak;
• Detect a possible Fuel Quantity Indication (FQI) failure.

However, even without any failure or fuel leak, some discrepancies which may be revealed during fuel checks. This may be due to:

• FQI tolerance;
• FU indication tolerance;
• Water freezing in the tanks.

Refer to OM Part B to determine acceptable discrepancies level.

Low Fuel Situation

If it becomes apparent en-route that the fuel remaining is close to the minimum amount required, the options available are to:

• Adjust the aircraft speed;
• Obtain a more direct routeing;
• Fly at a different flight level; and/or
• Select a closer alternate aerodrome.

If it is still not possible to arrive at the destination with the appropriate minimum fuel, landing and refuelling at suitable aerodrome shall be made.

If at any time, it becomes apparent that the aircraft may land with less than Final Reserve Fuel (30 minutes holding), advise ATC that any undue delay cannot be accepted. This is not an emergency situation but just an advisory that indicates an emergency situation is possible should any undue delay occur. ATC must thereafter be kept fully informed of the situation.

Important: A minimum fuel advisory does not imply a need for traffic priority. If at any time, it is evident that the aircraft will land with less than Final Reserve Fuel (30 minutes holding) remaining, Commander must declare emergency using following phrase: »MAYDAY, MAYDAY, MAYDAY, The Company xxx, DECLARING EMERGENCY DUE FUEL SHORTAGE, REMAINING FUEL FOR xx MINUTES, REQUEST IMMEDIATE LANDING AT xxxx!«.
Diversion to a nearest suitable aerodrome must be initiated immediately.

Fuel Freezing Limitations

The minimum fuel temperature, published in the operational documentation, may be more restrictive than the certified aircraft environmental envelope. It includes two different limitations both linked to engine operation:

Fuel freezing point limitation: this limitation provides an operating margin to prohibit operations under fuel temperature conditions that could result in the accumulation of waxy products in the fuel. The resulting limitation varies with the freezing point of the fuel being used. Aside from this, engines have a fuel warming (oil cooling) system at their inlet.

Because of the architecture of this system and the fact that the fuel inlet hardware varies from one engine type to another, the specification of what fuel temperature is acceptable at the inlet of the engine varies from one engine type to the other. Therefore, engine manufacturers sometime require a temperature margin to fuel freezing point to guarantee correct operation.

Note: The fuel anti-icing additives authorised by engine manufacturers decrease the freezing temperature of the water contained in the fuel, but have no effect on the fuel freezing temperature itself.

Therefore, the minimum fuel temperature should be fuel freezing point + engine manufacturer margin. If the actual freezing point of the fuel being used is unknown, the minimum fuel specification values as indicated below should be used as authorised by the AFM/FCOM.

• JET A1 = - 47°C

Fuel heat management system limitation: this limitation reflects the engine capability to warm-up a given water-saturated fuel flow to such a point that no accumulation of ice crystals may clog the fuel filter. Such a limitation does not appear in the documentation for some engine types when outside the environmental envelope. When applicable (refer to OM Part B) the resulting limitation is a fixed temperature, below which, a flight is not permitted.

The more restrictive of the two limitations above should be considered. Refer to FCOM regarding the procedures dealing with low fuel temperature. In general, whenever necessary the TAT has to be increased. This is achieved by an aeroplane speed increase and/or an altitude decrease.

Increasing the aeroplane speed provides a marginal TAT increase (in the order of 0.5 to 1ºC for 0.01 M increase) and thus a small fuel temperature increase, at the expense of a significant increase in fuel consumption.

Decreasing the altitude generally, provides a SAT increase (about 2ºC per 1.000 ft). Nevertheless, whenever the tropopause is substantially low, decreasing the altitude may not provide the corresponding expected SAT and, thus, TAT increase.

Fuel Conservation Methods

Reserved.