FUEL PLANNING – AN IMPORTANT FLIGHT SAFETY ASPECT


FUEL PLANNING – AN IMPORTANT FLIGHT SAFETY ASPECT

1.            Flight planning is the process of producing a flight plan to describe a proposed aircraft flight. It involves two safety-critical aspects: fuel calculation, to ensure that the aircraft can safely reach the destination, and compliance with air traffic control requirements, to minimize the risk of mid-air collision. In addition, flight planners normally wish to minimize flight cost by appropriate choice of route, height, and speed, and by loading the minimum necessary fuel on board. Fuel plan should aim maximum achievable cost savings.

2.            Fuel planning requires accurate weather forecasts so that fuel consumption calculations can account for the fuel consumption effects of head or tail winds and air temperature. Safety regulations require aircraft to carry fuel beyond the minimum needed to fly from origin to destination, allowing for unforeseen circumstances or for diversion to another location if the planned destination becomes unavailable.

3.            Producing an accurate optimized fuel plan requires a large number of calculations, so commercial flight planning systems make extensive use of computers.

4.            The basic purpose of a fuel planning is to calculate how much trip fuel is needed in the air navigation process by an aircraft when flying from an origin airport to a destination airport. Aircraft must also carry some reserve fuel to allow for unforeseen circumstances. This means that when the aircraft gets near the destination location, it must still have enough alternate fuel and alternate reserve available to fly on from there to the alternate location. Since the aircraft is not expected at the alternate location, it must also have enough holding fuel to circle for a while while a landing slot is found.

5.            Rate of fuel burn depends on ambient temperature, aircraft speed, and aircraft altitude, none of which are entirely predictable. Rate of fuel burn also depends on airplane weight, which changes as fuel is burned. The air temperature affects the efficiency/fuel consumption of aircraft engines. The wind may provide a head or tail wind component which in turn will increase or decrease the fuel consumption by increasing or decreasing the air distance to be flown. Note that a large aircraft such as a jumbo jet may burn up to 80 tons of fuel on a 10 hour flight, so there is a substantial weight change during the flight.

6.            Cruising at a higher flight level generally requires less fuel than at a lower flight level, but extra climb fuel may be needed to get up to the higher flight level.

7.            When an aircraft which encounters some emergency and has to land straight after taking off may have to circle for a while to use up fuel, or else jettison some fuel, or else land immediately and risk having the undercarriage collapse.

8.            Aircraft having more than one fuel tank, manufacturer provides rules as to how much fuel to load into each tank so as to avoid affecting the aircraft centre of gravity. Also, the fuel tanks have some maximum capacity. On some occasions, impossible flight plan is requested. The aircraft can’t possibly reach the intended destination, even with no cargo or passengers, since the fuel tanks are just not big enough to hold the amount of fuel needed; it would appear that some missions are over-optimistic at times, perhaps hoping for a (very) strong tailwind.

9.            Some military aircraft may refuel in mid-air. Such refueling is a gradual process rather than instantaneous. Flight plan should be flexible enough to allow for the change in fuel and show the effect on each aircraft involved.

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