aerospace engineering Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is s ...

, 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): :

\ \zeta = \frac

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

drop tank In aviation, a drop tank (external tank, wing tank or belly tank) is used to describe auxiliary fuel tanks externally carried by aircraft. A drop tank is expendable and often capable of being jettisoned. External tanks are commonplace on modern ...

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. Breguet’s aircraft

range Range may refer to: Geography * Range (geographic), a chain of hills or mountains; a somewhat linear, complex mountainous or hilly area (cordillera, sierra) ** Mountain range, a group of mountains bordered by lowlands * Range, a term used to i ...

equation describes the relationship of range with

airspeed In aviation, airspeed is the speed of an aircraft relative to the air it is flying through (which itself is usually moving relative to the ground due to wind). In contrast, the ground speed is the speed of an aircraft with respect to the sur ...

lift-to-drag ratio In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the Lift (force), lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficie ...

, 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. In this context, the Breguet range is proportional to

-\ln(1-\ \zeta)

Fighter aircraft

At today’s state of the art for jet

fighter aircraft Fighter aircraft (early on also ''pursuit aircraft'') are military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air supremacy, air superiority of the battlespace. Domina ...

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

supercruise Supercruise is sustained supersonic flight of a supersonic aircraft without using afterburner. Many supersonic military aircraft are not capable of supercruise and can maintain Mach 1+ flight only in short bursts with afterburners. Aircraft s ...

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

F-22 Raptor The Lockheed Martin/Boeing F-22 Raptor is an American twin-engine, jet-powered, all-weather, supersonic stealth fighter aircraft. As a product of the United States Air Force's Advanced Tactical Fighter (ATF) program, the aircraft was de ...

’s fuel fraction is 29 percent,

Eurofighter The Eurofighter Typhoon is a European multinational twin-engine, supersonic, canard delta wing, multirole fighter. The Typhoon was designed originally as an air-superiority fighter and is manufactured by a consortium of Airbus, BAE Systems ...

is 31 percent, both similar to those of the subcruising

F-4 Phantom II The McDonnell Douglas F-4 Phantom II is an American tandem two-seat, twin-engine, all-weather, long-range supersonic jet interceptor and fighter-bomber that was developed by McDonnell Aircraft for the United States Navy.Swanborough and Bower ...

F-15 Eagle The McDonnell Douglas F-15 Eagle is an American twin-engine, all-weather fighter aircraft designed by McDonnell Douglas (now part of Boeing). Following reviews of proposals, the United States Air Force (USAF) selected McDonnell Douglas's des ...

and the Russian

Mikoyan MiG-29 The Mikoyan MiG-29 (; NATO reporting name: Fulcrum) is a twin-engine fighter aircraft designed in the Soviet Union. Developed by the Mikoyan design bureau as an air superiority fighter during the 1970s, the MiG-29, along with the larger Suk ...

"Fulcrum". The Russian supersonic interceptor, the

Mikoyan MiG-31 The Mikoyan MiG-31 (; NATO reporting name: Foxhound) is a supersonic interceptor aircraft developed for the Soviet Air Forces by the Mikoyan design bureau as a replacement for the earlier MiG-25 "Foxbat"; the MiG-31 is based on and shares de ...

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

Panavia Tornado The Panavia Tornado is a family of twin-engine, variable-sweep wing multi-role combat aircraft, jointly developed and manufactured by Italy, the United Kingdom and Germany. There are three primary #Variants, Tornado variants: the Tornado IDS ...

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

Civilian Aircraft

Airliners have a fuel fraction of less than half their takeoff weight, between 26% for

medium-haul In aviation, the flight length or flight distance refers to the distance of a flight. Aircraft do not necessarily follow the great-circle distance, but may opt for a longer route due to weather, traffic, to utilise a jet stream, or to refuel. Co ...

to 45% for

long-haul In aviation, the flight length or flight distance refers to the distance of a flight. Aircraft do not necessarily follow the great-circle distance, but may opt for a longer route due to weather, traffic, to utilise a jet stream, or to refuel. Co ...

General aviation

The

Rutan Voyager The Rutan Model 76 Voyager was the first aircraft to fly around the world without stopping or refueling. It was piloted by Dick Rutan and Jeana Yeager. The flight took off from Edwards Air Force Base's 15,000 foot (4,600 m) runway in the Moja ...

took off on its

1986 The year 1986 was designated as the International Year of Peace by the United Nations. Events January * January 1 ** Aruba gains increased autonomy from the Netherlands by separating from the Netherlands Antilles. ** Spain and Portugal en ...

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

Steve Fossett James Stephen Fossett (April 22, 1944 – September 3, 2007) was an American businessman and a record-setting aviator, sailor, and adventurer. He was the first person to fly solo nonstop around the world in a balloon and in a fixed-wing aircraf ...

Virgin Atlantic GlobalFlyer The Scaled Composites Model 311 Virgin Atlantic GlobalFlyer (Aircraft registration, registered N277SF) is an aircraft designed by Burt Rutan in which Steve Fossett first flew a solo nonstop airplane flight around the world in slightly more than ...

could attain a fuel fraction of nearly 83 percent, meaning that it carried more than five times its empty weight in fuel.

References

{{reflist Aerospace engineering

Fighter aircraft

Civilian Aircraft

General aviation

See also

References