# Fuel fraction

With a fuel fraction of nearly 85%, the GlobalFlyer could carry 5 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]

${\displaystyle \ \zeta ={\frac {\Delta W}{W_{1}}}}$

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

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

Airliners have a fuel fraction of less than half their takeoff weight, between 26% for medium-haul to 45% for long-haul:

Model MTOW (t) OEW (t) OEW
Fraction
Fuel
capacity (t)
Fuel
fraction
Max. (t)
fraction
Airbus A380[7] 575 285 49.6% 254 44.2% 84 14.6%
Boeing 777-300ER[8] 351.5 167.8 47.7% 145.5 41.4% 69.9 19.9%
Boeing 777-200LR[8] 347.5 145.2 41.8% 145.5 41.9% 64.0 18.4%
Airbus A350-1000[9] 308 156 50.6% 122.5 39.8% 64 20.8%
Airbus A350-900[9] 280 142.7 51% 108.3 38.7% 53 18.9%
Boeing 787-9[10] 254 128.9 50.7% 101.5 40% 52.6 20.7%
Airbus A330-300[11] 242 130 53.7% 109.2 45.1% 45 18.6%
Airbus A330-200[11] 242 121 50% 109.2 45.1% 49 20.2%
Boeing 787-8[10] 227.9 120 52.7% 101.3 44.4% 43.3 19%
Airbus A320ceo[12] 79 44.3 56.1% 23.3 29.5% 20 25.3%
Boeing 737-800[13] 79 41.4 52.4% 20.9 26.5% 21.3 27%
Bombardier CS300[14] 67.6 37.1 54.9% 17.2 25.5% 18.7 27.7%
Bombardier CS100[14] 60.8 35.2 57.9% 17.6 29% 15.1 24.9%

The Concorde supersonic transport had a fuel fraction of 51%.

## General aviation

The Rutan Voyager took off on its 1986 around-the-world flight at 72 percent, the highest figure ever at the time.[15] 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.[16]

## References

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 Archived 2007-04-21 at the Wayback Machine 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. ^ "A380 Aircraft Characteristics – Airport and Maintenance Planning" (PDF). Airbus. December 2016.
8. ^ a b 777-200LR/-300ER/-Freighter Airplane Characteristics for Airport Planning (PDF) (Technical report). Boeing. May 2015.
9. ^ a b "A350 Aircraft Characteristics – Airport and Maintenance Planning" (PDF). Airbus. November 2016. Archived from the original (PDF) on 2016-11-28.
10. ^ a b "787 Airplane Characteristics for Airport Planning" (PDF). Boeing. December 2015.
11. ^ a b "A330 Aircraft Characteristics – Airport and Maintenance Planning" (PDF). Airbus. December 2016.
12. ^ "A320 Aircraft Characteristics – Airport and Maintenance Planning" (PDF). Airbus. June 2016.
13. ^ "737 Airplane Characteristics for Airport Planning" (PDF). Boeing. September 2013.
14. ^ a b "CSeries brochure" (PDF). Bombardier. June 2015. Archived from the original (PDF) on 2015-09-08. Retrieved 2017-10-22.
15. ^ Noland, David (February 2005). "Burt Rutan and the Ultimate Solo". Popular Mechanics. Archived from the original on 2006-12-11.
16. ^ 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.