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Fuel - Preflight Planning

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Article Information
Category: General General
Content source: SKYbrary About SKYbrary
Content control: SKYbrary About SKYbrary

Description

Preflight fuel planning is the process of determining the appropriate amount of fuel to be loaded for a specific flight. Fuel planning can be accomplished manually by referring to the appropriate charts and graphs or electronically utilizing a fuel planning programme or service. In either case, preflight fuel planning should ensure compliance with Regulatory requirements, Company policy where applicable and with the day of flight specific criteria of aircraft, crew, payload, fuel tankering, de-icing requirements, origin, route, notified airspace, destination, alternates, Notice To Airmen and weather.

Threats

  • Insufficient Fuel - Inadequate or incomplete preflight fuel planning can result in the calculation of a total fuel requirement which is not actually sufficient for the planned flight.
  • Excessive Fuel - Inadequate or incomplete preflight fuel planning or non-compliance with Company policy or manufacturer limitations can result in the calculation of a total fuel figure well in excess of that actually required for the intended flight.

Effects

The potential effects of insufficient fuel are numerous. They include:

  • The requirement to return to the gate at origin due to fuel falling below minimum brake release fuel prior to departure.
  • Aircraft turnback due to insufficient fuel to reach destination.
  • Enroute diversion due to insufficient fuel for continuation of the flight.
  • "Pushing" the weather under VFR rules due to insufficient fuel to meet IFR requirements.
  • Breaking IFR limits on approach due to insufficient fuel to reach an alternate aerodrome.
  • The requirement to declare an emergency situation (PAN or MAYDAY as appropriate) due to fuel depletion.
  • Regulatory enforcement action against the Company and/or crew for non-compliance with fuel requirement regulations.
  • Engine failure due to fuel starvation.

The potential effects of excessive fuel include:

  • Exceedence of an aircraft limitation - maximum takeoff weight or maximum landing weight.
  • Increased operating cost due to the increased fuel burn resulting from the carriage of the additional weight in fuel.

Defences

The principal defence against both of the aforementioned threats and virtually all of the listed effects is a comprehensive preflight fuel planning process. The process must ensure compliance with Regulatory fuel requirements for the type of flight and the area of operations. To do this, it should incorporate any Company mandated policies or requirements and consider each of the following factors to determine a legally appropriate and operationally prudent fuel figure.

  • Aircraft limitations
    • Maximum takeoff weight (both structural and performance limited) must be considered.
    • Maximum landing weight (based on calculated fuel burn) must be respected.
  • Aircraft status
    • Fuel consumption penalties specific to the aircraft scheduled for the flight must be taken into consideration.
    • Any Minimum Equipment List (MEL) or Configuration Deviation List fuel penalties must be applied to the fuel calculations.
    • Do any MEL items limit aircraft altitude, impose restrictions on maximum weights or affect All Weather capability?
  • Payload
    • What is the best available estimate for the aircraft zero fuel weight (ZFW)?
    • Is fuel tankering required for operational reasons (ballast/fuel unavailable at destination) or prudent for financial reasons (cost differential)?
    • Has additional fuel for ETOPS or remote destination operations been taken into consideration?
  • Crew
    • What is the crew configuration? Is it the standard for the aircraft type or are there supernumary crew members on the flight deck or in the cabin?
    • Are both flight deck crew members qualified to conduct Low Visibility Procedures (LVP)?
    • Can the crew fly to published departure/approach limits or, as might be in the case of a newly promoted Captain, do they have higher limits imposed?
  • Departure Aerodrome
    • What is the average taxi time/fuel burn appropriate to the departure aerodrome?
    • Are additional delays likely due to factors such as weather, time of day, anticipated departure runway or de-icing requirements?
      • Are de-icing procedures accomplished at the gate or at a remote location?
      • Is de-icing accomplished with engines running or engines shut down?
  • Route
    • What is the expected SID?
    • What is the anticipated route?
    • Are enroute delays expected?
    • Have any required enroute or ETOPS alternates been identified?
    • What is the anticipated STAR?
    • If the SID/STAR information is uncertain, does the plan allow for the worst case scenario?
  • Destination Aerodrome
    • Are arrival delays anticipated? If so, how long?
    • What is the anticipated runway in use?
    • Is the lenght of the landing surface adequate for the expected landing weight under the anticipated runway surface conditions at the estimated time of arrival?
  • Alternate Aerodrome
    • How many alternates are required?
    • Is No Alternate IFR flight an option?
    • What are the opening/closing times?
    • Is aerodrome capacity likely to be exceeded in the event of multiple diverting aircraft?
  • NOTAMS
    • Are any of the planned use aerodromes affected by any limiting NOTAMS?
      • Airfield closures or changes to hours of operation
      • Construction which limits runway length or runway closures
      • Changes to published approach, arrival or departure procedures
      • Navigation aids out of service
      • Altitude reservations or temporary airspace restrictions or closures
      • Changes in fuel availability
  • Weather
    • Do the forecast and actual wind and weather at the planned use aerodromes meet legal requirements?
    • If destination wind or weather are marginal, has additional holding fuel been considered?
    • Is the forecast weather for the planned use aerodromes likely to result in delays?
    • What are the enroute winds and temperatures?
    • Is there enroute weather or conditions that are likely to result in additional fuel burn (track deviation for CBs, in-flight icing etc)?

Typical Scenarios

  • The owner of a light general aviation aircraft loads a specific amount of fuel for a route that he has flown numerous times previously and departs without making a comprehensive review of the weather conditions. The winds are significantly stronger than usual extending the time enroute beyond the endurance provided by the fuel available.
  • Flight planning for an international scheduled flight is conducted without first determining the maintenance status of the assigned aircraft. Fuel is ordered as per the flight plan and loaded onto the aircraft. On arrival at the gate, the pilots determine that there is an MEL deferal against the aircraft for an unserviceable airconditioning pack which limits the cruise altitude to a maximum of FL310. There is insufficient fuel on board to conduct the flight at the restricted altitude and the planned zero fuel weight for the aircraft does not permit uplifting the additional required fuel without exceeding takeoff performance limitations. As a result, the payload has to be reduced. the flight replanned/refiled at the restricted altitude and additional fuel uplifted. A departure delay is incurred.

Contributory Factors

Effective preflight fuel planning can be hindered by time constraints, changing weather, poor communications, missing or inaccurate load or maintenance information as well as complacency on the part of the dispatchers or pilots.

Solutions

Effective preflight fuel planning is only possible when a properly trained and motivated staff have a comprehensive understanding of regulations, Company policy and aircraft limitations and have timely access to all required information inclusive of (but not limited to) weather, payload, maintenance status, crew limitations and departure, route and arrival delays and restrictions.

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