Fuel fraction

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This article is about flight vehicles. For the topic in combustion physics, see fuel mass fraction.
The GlobalFlyer had a fuel fraction near 85% — it could carry five times its weight in fuel.

In aerospace engineering, an aircraft's fuel fraction, fuel weight fraction,[1] or a spacecraft's propellant fraction, is the weight of the fuel or propellant divided by the gross take-off weight of the craft (including propellant):[2]

The fractional result of this mathematical division is often expressed as a percent. For aircraft with external drop tanks, the term internal fuel fraction is used to exclude the weight of external tanks and fuel.

Fuel fraction is a key parameter in determining an aircraft's range, the distance it can fly without refueling. Breguet’s aircraft range equation describes the relationship of range with airspeed, lift-to-drag ratio, specific fuel consumption, and the part of the total fuel fraction available for cruise, also known as the cruise fuel fraction, or cruise fuel weight fraction.[3]

Fighter aircraft[edit]

At today’s state of the art for jet fighter aircraft, fuel fractions of 29 percent and below typically yield subcruisers; 33 percent provides a quasi–supercruiser; and 35 percent and above are needed for useful supercruising missions. The U.S. F-22 Raptor’s fuel fraction is 29 percent,[4] Eurofighter is 31 percent, both similar to those of the subcruising F-4 Phantom II, F-15 Eagle and the Russian Mikoyan MiG-29 "Fulcrum". The Russian supersonic interceptor, the Mikoyan MiG-31 "Foxhound", has a fuel fraction of over 45 percent.[5] The Panavia Tornado had a relatively low internal fuel fraction of 26 percent, and frequently carried drop tanks.[6]


Airliners typically have a fuel fraction between 25 and 45 percent, so less than half their takeoff weight is fuel. The Boeing 777-200-IGW very long range airliner has a fuel fraction of 47 percent.[7] The Concorde supersonic transport had a high fuel fraction of around 55%.[8] Short-mid range airliners, like an Airbus A-320 has a fuel fraction of 14,3% . (For aircraft type with a maximum weight of 73500 kgrs. )

General aviation[edit]

The Rutan Voyager took off on its 1986 around-the-world flight at 72 percent, the highest figure ever at the time.[9] Steve Fossett's Virgin Atlantic GlobalFlyer could attain a fuel fraction of nearly 85 percent, meaning that it carried more than five times its empty weight in fuel.[10]

See also[edit]


  1. ^ Brandt, Steven (2004). Introduction to Aeronautics: a Design Perspective. AIAA (American Institute of Aeronautics & Ast). p. 359. ISBN 1-56347-701-7. 
  2. ^ Vinh, Nguyen (1993). Flight Mechanics of High-Performance Aircraft. Cambridge: Cambridge University Press. p. 139. ISBN 0-521-47852-9. 
  3. ^ Filippone, Antonio (2006). Flight Performance of Fixed and Rotary Wing Aircraft. Elsevier. p. 426. ISBN 0-7506-6817-2. 
  4. ^ 8200/27900 = 0.29
  5. ^ The F-22 Program FACT VERSUS FICTION by Everest E. Riccioni, Col. USAF, Ret.
  6. ^ Spick, Mike (2002). Brassey's Modern Fighters. Washington: Potomac Books. pp. 51–53. ISBN 1-57488-462-X. 
  7. ^ The Sonic Cruiser – A Concept Analysis by Dr. Martin Hepperle
  8. ^ Manned Sub-Orbital Space Transportation Vehicles
  9. ^ Noland, David (February 2005). "Burt Rutan and the Ultimate Solo". Popular Mechanics. 
  10. ^ Schneider, Mike (2006-02-06). "Adventurer Set for Record-Setting Flight". Space.com. Associated Press. Retrieved 2007-03-18. At takeoff, fuel is expected to account for almost 85 percent of the graphite-made aircraft's weight.