Fuel fraction
{{About|flight vehicles|the topic in combustion physics|fuel mass fraction}}
File:GlobalFlyer at KSC before launch.jpg could carry 5 times its weight in fuel.]]
In aerospace engineering, an aircraft's fuel fraction, fuel weight fraction,{{cite book | last = Brandt | first = Steven | title = Introduction to Aeronautics: a Design Perspective | publisher = AIAA (American Institute of Aeronautics & Ast) | page = 359 | year = 2004 | isbn = 1-56347-701-7 }} 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):{{cite book | last = Vinh | first = Nguyen | title = Flight Mechanics of High-Performance Aircraft | url = https://archive.org/details/flightmechanicsh00vinh | url-access = limited | publisher = Cambridge University Press | location = Cambridge | page = [https://archive.org/details/flightmechanicsh00vinh/page/n153 139]| year = 1993 | isbn = 0-521-47852-9 }}
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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.{{cite book
|title=Flight Performance of Fixed and Rotary Wing Aircraft
|author=Filippone, Antonio
|year=2006
|publisher=Elsevier
|page=426
|isbn=0-7506-6817-2}}
In this context, the Breguet range is proportional to
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,[https://web.archive.org/web/20050908090849/http://www.af.mil/factsheets/factsheet.asp?fsID=199 8200/27900 = 0.29] 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.[http://www.pogo.org/p/defense/do-000812-f22.htm The F-22 Program FACT VERSUS FICTION] {{webarchive|url=https://web.archive.org/web/20070421194617/http://www.pogo.org/p/defense/do-000812-f22.htm |date=2007-04-21 }} by Everest E. Riccioni, Col. USAF, Ret. The Panavia Tornado had a relatively low internal fuel fraction of 26 percent, and frequently carried drop tanks.{{cite book | last = Spick | first = Mike | title = Brassey's Modern Fighters | publisher = Potomac Books | location = Washington | year = 2002 | pages = 51–53 | isbn = 1-57488-462-X }}
Civilian Aircraft
Airliners have a fuel fraction of less than half their takeoff weight, between 26% for medium-haul to 45% for long-haul.
General aviation
The Rutan Voyager took off on its 1986 around-the-world flight at 72 percent, the highest figure ever at the time.{{cite journal
|journal = Popular Mechanics
|title = Burt Rutan and the Ultimate Solo
|author = Noland, David
|date = February 2005
|url = http://www.popularmechanics.com/science/air_space/1262012.html?page=3
|url-status = dead
|archiveurl = https://web.archive.org/web/20061211202755/http://www.popularmechanics.com/science/air_space/1262012.html?page=3
|archivedate = 2006-12-11
}} Steve Fossett's Virgin Atlantic GlobalFlyer could attain a fuel fraction of nearly 83 percent, meaning that it carried more than five times its empty weight in fuel.
See also
References
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