In aerospace engineering

Aerospace engineering

Aerospace engineering is the primary branch of engineering concerned with the design, construction and science of aircraft and spacecraft. It is divided into two major and overlapping branches: aeronautical engineering and astronautical engineering...

, an aircraft's fuel fraction, fuel weight fraction, 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):


The fractional result of this mathematical division is often expressed as a percent. For aircraft with external drop tank

Drop tank

In aeronautics, a drop tank is used to describe auxiliary fuel tanks externally carried by aircraft. A drop tank is expendable and often jettisonable...

s, 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

Range (aircraft)

The maximal total range is the distance an aircraft can fly between takeoff and landing, as limited by fuel capacity in powered aircraft, or cross-country speed and environmental conditions in unpowered aircraft....

.
Breguet

Louis Charles Breguet

Louis Charles Breguet was a French aircraft designer and builder, one of the early aviation pioneers.- Biography :...

’s aircraft range

Range (aircraft)

The maximal total range is the distance an aircraft can fly between takeoff and landing, as limited by fuel capacity in powered aircraft, or cross-country speed and environmental conditions in unpowered aircraft....

 equation describes the relationship of range with airspeed

Airspeed

Airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: indicated airspeed , calibrated airspeed , true airspeed , equivalent airspeed and density airspeed....

, lift-to-drag ratio

Lift-to-drag ratio

In aerodynamics, the lift-to-drag ratio, or L/D ratio, is the amount of lift generated by a wing or vehicle, divided by the drag it creates by moving through the air...

, specific fuel consumption

Specific fuel consumption

Thrust specific fuel consumption or sometimes simply specific fuel consumption, SFC, is an engineering term that is used to describe the fuel efficiency of an engine design with respect to thrust output...

, and the part of the total fuel fraction available for cruise, also known as the cruise fuel fraction, or cruise fuel weight fraction.

Fighter aircraft

At today’s state of the art for jet fighter aircraft

Fighter aircraft

A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...

, fuel fractions of 29 percent and below typically yield subcruisers; 33 percent provides a quasi–supercruise

Supercruise

Supercruise is sustained supersonic flight of an aircraft with a useful cargo, passenger, or weapons load performed efficiently and without the use of afterburners ....

r; and 35 percent and above are needed for useful supercruising missions. The U.S. F-22 Raptor

F-22 Raptor

The Lockheed Martin/Boeing F-22 Raptor is a single-seat, twin-engine fifth-generation supermaneuverable fighter aircraft that uses stealth technology. It was designed primarily as an air superiority fighter, but has additional capabilities that include ground attack, electronic warfare, and signals...

’s fuel fraction is 29 percent , Eurofighter is 31 percent, both similar to those of the subcruising F-4 Phantom II

F-4 Phantom II

The McDonnell Douglas F-4 Phantom II is a tandem two-seat, twin-engined, all-weather, long-range supersonic jet interceptor fighter/fighter-bomber originally developed for the United States Navy by McDonnell Aircraft. It first entered service in 1960 with the U.S. Navy. Proving highly adaptable,...

, F-15 Eagle

F-15 Eagle

The McDonnell Douglas F-15 Eagle is a twin-engine, all-weather tactical fighter designed by McDonnell Douglas to gain and maintain air superiority in aerial combat. It is considered among the most successful modern fighters with over 100 aerial combat victories with no losses in dogfights...

 and the Russian Mikoyan MiG-29

Mikoyan MiG-29

The Mikoyan MiG-29 is a fourth-generation jet fighter aircraft designed in the Soviet Union for an air superiority role. Developed in the 1970s by the Mikoyan design bureau, it entered service with the Soviet Air Force in 1983, and remains in use by the Russian Air Force as well as in many other...

 "Fulcrum". The Russian supersonic interceptor, the Mikoyan MiG-31

Mikoyan MiG-31

The Mikoyan MiG-31 is a supersonic interceptor aircraft developed to replace the MiG-25 "Foxbat". The MiG-31 was designed by the Mikoyan design bureau based on the MiG-25.-Development:...

 "Foxhound", has a fuel fraction of over 45 percent. The Panavia Tornado

Panavia Tornado

The Panavia Tornado is a family of twin-engine, variable-sweep wing combat aircraft, which was jointly developed and manufactured by the United Kingdom, West Germany and Italy...

 had a relatively low internal fuel fraction of 26 percent, and frequently carried drop tanks.

Airliners

Airliners typically have a fuel fraction between 25 to 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. The Concorde

Concorde

Aérospatiale-BAC Concorde was a turbojet-powered supersonic passenger airliner, a supersonic transport . It was a product of an Anglo-French government treaty, combining the manufacturing efforts of Aérospatiale and the British Aircraft Corporation...

 supersonic transport

Supersonic transport

A supersonic transport is a civilian supersonic aircraft designed to transport passengers at speeds greater than the speed of sound. The only SSTs to see regular service to date have been Concorde and the Tupolev Tu-144. The last passenger flight of the Tu-144 was in June 1978 with its last ever...

 had a high fuel fraction of around 55%.

General aviation

The Rutan Voyager took off on its 1986

1986 in aviation

This is a list of aviation-related events from 1986:-January:* January 9 - the UK Defence Secretary, Michael Heseltine, resigns amidst a political furore over the future of Westland Helicopters...

 around-the-world flight at 72 percent, the highest figure ever at the time. Steve Fossett

Steve Fossett

James Stephen Fossett was an American commodities trader, businessman, and adventurer. Fossett is the first person to fly solo nonstop around the world in a balloon...

's Virgin Atlantic GlobalFlyer

Virgin Atlantic GlobalFlyer

The Scaled Composites Model 311 Virgin Atlantic GlobalFlyer is an aircraft designed by Burt Rutan in which Steve Fossett flew a solo nonstop airplane flight around the world in a time of 67 hours 1 minute from February 28, 2005 until March 3, 2005...

could attain a fuel fraction of nearly 85 percent, meaning that it carried more than five times its empty weight in fuel.