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Fuel - Flight Planning Definitions

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Category: General General
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Description

As in many facets of aviation, Fuel Planning has a list of specific terms and definitions of its own. The following list identifies the most critical of these terms. Different terms or names for the same concept are often used interchangeably by different regulatory authorities or flight planning organizations. The most common of these variants preface the definitions that follow.

Definitions

Additional Fuel

Additional fuel is fuel which is added to comply with a specific regulatory or company requirement. Examples include ETOPS fuel, fuel required for a remote or island destination where no alternate is available and fuel required to satisfy an Minimum Equipment List (MEL) or Configuration Deviation List performance penalty.

Alternate Fuel

Alternate fuel is the amount of fuel required from the missed approach point at the destination aerodrome until landing at the alternate aerodrome. It takes into account the required fuel for:

  • Missed approach at the destination airport
  • Climb to enroute altitude, cruise and descent at alternate aerodrome
  • Approach at alternate
  • Landing at the alternate aerodrome

When two alternates are required by the Authority, alternate fuel must be sufficient to proceed to the alternate which requires the greater amount of fuel.

Ballast Fuel

Ballast fuel is sometimes carried to maintain the aircraft centre of gravity within limits. In certain aeroplanes, a zero fuel weight above a defined threshold requires that a minimum amount of fuel be carried in the wings through all phases of flight to prevent excessive wing bending. In both cases, this fuel is considered ballast and, under anything other than emergency circumstances, is not to be burned during the flight.

Block Fuel / Ramp Fuel / Total Fuel On Board

Block fuel is the total fuel required for the flight and is the sum of the Taxi fuel, the Trip fuel, the Contingency fuel, the Alternate fuel, the Final Reserve fuel, the Additional fuel and any Extra fuel carried.

Contingency Fuel / Route Reserve

Contingency fuel is carried to account for additional enroute fuel consumption caused by wind, routing changes or ATM: ATM/CNS restrictions. According to ICAO Annex 6, the recommended minimum contingency fuel is the greater of 5% of the trip fuel or 5 minutes holding consumption at 1500' above destination airfield elevation computed based on calculated arrival weight. However, some regulators have eliminated the minimum time requirement and some have increased the recommended time interval in their National Regulations. As well, some regulators allow contingency fuel reduction to 3% of trip fuel, or to specific time increments, with use of enroute alternates and conditional upon demonstrated performance criteria from the Operator. At least one authority allows, under very specific circumstances, for contingency fuel to be reduced to 0. In all cases, an Operator can direct that its crews carry contingency fuel in excess of that required by their National Aviation Authority (NAA).

Extra Fuel

Fuel added at the discretion of the Captain and/or the dispatcher

Final Reserve Fuel / Fixed Reserve Fuel / Holding Fuel

Final reserve fuel is the minimum fuel required to fly for 30 minutes at 1,500 feet above the alternate aerodrome or, if an alternate is not required, at the destination aerodrome at holding speed in ISA conditions. Some Regulating Authorities require sufficient fuel to hold for 45 minutes.

Minimum Brake Release Fuel

Minimum brake release fuel is that quantity of fuel which, at the commencement of the takeoff roll, complies with all regulatory requirements for the flight in question. This is the minimum legal fuel required for departure.

Reserve Fuel / Minimum Diversion Fuel

Reserve fuel is the sum of Alternate fuel plus Final Reserve fuel.

Taxi Fuel

Taxi fuel is the fuel used prior to takeoff and will normally include pre-start APU consumption, engine start and taxi fuel. Taxi fuel is usually a fixed quantity for an average taxi duration. However, local conditions at the departure aerodrome such as average taxi time, normal ground delays and any anticipated deicing delays should be taken into consideration and the taxi fuel adjusted accordingly.

Trip Fuel / Burn / Fuel to Destination

The Trip fuel is the required fuel quantity from brake release on takeoff at the departure aerodrome to the landing touchdown at the destination aerodrome. This quantity includes the fuel required for:

  • Takeoff
  • Climb to cruise level
  • Flight in level cruise including any planned step climb or step descent
  • Flight from the beginning of descent to the beginning of approach,
  • Approach
  • Landing at the destination

Trip fuel must be adjusted to account for any additional fuel that would be required for known ATS restrictions that would result in delayed climb to or early descent from planned cruising altitude.

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