Sylvie Willis
The General Electric J85 is a small, single-shaft turbojet engine that is one of GE's most successful and longest-serving military jet engines. The J85 was originally designed to power a large decoy missile, the McDonnell ADM-20 Quail. The specific fuel consumption of the J85 engine depends on a variety of factors, including the additional equipment, specific model, and flight conditions. For example, the F-16 Fighting Falcon, a widely used fighter jet, consumes approximately 3,800 liters of fuel per hour when flying at high altitudes, while the F-22 Raptor, a fifth-generation aircraft, can exceed 8,000 liters per hour due to its vectored thrust and stealth technology. Speed and altitude also play a significant role in fuel consumption, with supersonic speeds and low altitudes resulting in higher fuel usage. Additionally, the type of fuel used, such as JP-8, a kerosene-based jet fuel widely used by the US military, can impact fuel efficiency and engine performance.
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What You'll Learn
The General Electric J85 jet engine consumes 400 US gallons of fuel per hour at full throttle
The General Electric J85 is a small single-shaft turbojet engine. It is one of GE's most successful and longest-serving military jet engines, with civilian versions having logged over 16.5 million hours of operation. The basic engine design is quite small, measuring about 17.7 inches (45 cm) in diameter and 45.4 inches (115 cm) in length. It features an eight-stage axial-flow compressor powered by two turbine stages.
The J85 engine is capable of producing up to 2,100 lbf (9.3 kN) of dry thrust, and even more with an afterburner. Military versions can generate up to 3,500 lbf (16 kN) of thrust, while afterburning variants can reach up to 5,000 lbf (22 kN). The engine's weight varies depending on additional equipment and the specific model, ranging from 300 to 500 pounds (140 to 230 kg).
At full throttle at sea level, the J85 engine consumes approximately 400 US gallons (1,500 litres) of fuel per hour. This significant fuel consumption is due to the engine's high-performance capabilities.
The J85 has been used to power a range of small jet aircraft, including the Northrop T-38 Talon, Northrop F-5, Canadair CT-114 Tutor, and Cessna A-37 Dragonfly light attack aircraft. More recently, the J85 has powered aircraft such as the Scaled Composites White Knight and the carrier for the Scaled Composites SpaceShipOne spacecraft.
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The US military uses 5 billion gallons of JP-8 jet fuel annually
JP-8, or Jet Propellant 8, is a jet fuel used widely by the US military. It is also known as F-34 by NATO. The US military and the North Atlantic Treaty Organization (NATO) forces use an estimated 5 billion gallons of JP-8 jet fuel each year. The US Air Force replaced JP-4 with JP-8 to use a less flammable and less hazardous fuel for better safety and combat survivability.
JP-8 is a kerosene-based multipurpose fuel. It is used in all US military aircraft (except Navy ship-based aircraft, which use JP-5), ground vehicles, and support equipment such as generators, cooking stoves, and tent heaters. It is also used as a coolant in engines and some other aircraft components. The use of JP-8 helps to eliminate logistical problems associated with transporting and distributing multiple types of fuel to various bases within the United States.
JP-8 is similar to commercial aviation's Jet A-1 fuel but with the addition of corrosion inhibitors and anti-icing additives. It was first introduced at NATO bases in 1978. Installations in Alaska still use JP-8 instead of Jet A-1 due to its better performance in cold weather.
The use of JP-8 in highly turbocharged diesel engines can cause issues during cold starts and idling due to low compression temperatures and ignition delays. This is because the cetane index is not specified in MIL-DTL-83133G to 40 or higher. Modern common-rail diesel engines may also experience wear problems in high-pressure fuel pumps and injectors due to the lack of lubricity specified in the MIL-DTL-83133G standard.
The General Electric J85 is a small single-shaft turbojet engine used in several aircraft, including the Northrop T-38 Talon, Northrop F-5, and Cessna A-37 Dragonfly. The basic engine design is quite small, with a diameter of 17.7 inches (45 cm) and a length of 45.4 inches (115 cm). It can generate up to 2,100 lbf (9.3 kN) of dry thrust and consumes approximately 400 US gallons (1,500 L) of fuel per hour at full throttle at sea level without an afterburner.
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JP-8 jet fuel is kerosene-based
The General Electric J85 is a small single-shaft turbojet engine that powers small jet aircraft. The basic engine design is quite compact, measuring about 17.7 inches (45 cm) in diameter and 45.4 inches (115 cm) in length. The J85 engine is capable of producing up to 2,100 lbf (9.3 kN) of dry thrust, and higher thrust levels with an afterburner. When operating at full throttle at sea level without the afterburner, the J85 engine consumes approximately 400 US gallons (1,500 litres) of fuel per hour.
JP-8, or Jet Propellant 8, is a kerosene-based jet fuel with additives to enhance its performance for military use. It is widely used by the US military and was introduced at NATO bases in 1978. The additives in JP-8 include corrosion inhibitors, anti-icing agents, lubricants, and antistatic agents, which improve its performance in cold weather environments. The use of JP-8 fuel offers advantages such as reduced flammability and lower hazard levels, contributing to enhanced safety and combat survivability.
JP-8 is derived from kerosene, which is produced through the distillation of crude oil at atmospheric pressure or from catalytic, thermal, or steam cracking of heavier petroleum streams. The resulting kerosene is then combined with additives to create JP-8 jet fuel. This process ensures that the final product meets the required specifications for military use.
The performance and regulatory requirements for jet fuel are defined by organisations such as ASTM International and the U.K. Ministry of Defense. These organisations publish specifications and test methods for commercial jet fuels, providing guidelines for fuel composition and quality. The additives included in JP-8 jet fuel are chosen to meet these standards and enhance its performance in military aircraft.
The use of JP-8 jet fuel in diesel engines has been associated with some challenges, including reduced torque and fuel economy due to its lower density and viscosity compared to diesel fuel. However, engine modifications can be implemented to address these issues. Additionally, the lower volatility of JP-8 fuel compared to standard diesel fuel can result in prolonged exposure risks, as it remains on contaminated surfaces for extended periods.
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The US Air Force replaced JP-4 with JP-8 fuel by 1995
The J85 is a small single-shaft turbojet engine that was originally designed to power a large decoy missile. Military versions of the J85 can produce up to 3,500 pounds of thrust dry, and afterburning variants can reach up to 5,000 pounds. At full throttle at sea level, the J85 engine, without an afterburner, consumes approximately 400 US gallons of fuel per hour.
The US Air Force replaced JP-4 with JP-8 jet fuel by the end of 1995. JP-8, or Jet Propellant 8, is a kerosene-based jet fuel widely used by the US military. The switch was made to improve safety and combat survivability as JP-8 is less flammable and hazardous than JP-4. It was first introduced at NATO bases in 1978 and its NATO code is F-34.
JP-8 is similar to commercial aviation's Jet A-1 fuel but includes additional corrosion inhibitor and anti-icing additives. It is also used as a coolant in engines and other aircraft components. Additionally, JP-8 is used in US Army heaters and stoves. The US military services and NATO forces use an estimated 5 billion gallons of JP-8 each year.
In 2014, the US Air Force completed the process of converting all JP-8 installations within the continental US to use commercial Jet A-1 fuel with additional additives. However, installations in Alaska continue to use JP-8 due to its better performance in cold weather.
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The J85 jet engine is small, weighing 300-500 pounds
The J85 jet engine, also known as the “Little Tough Guy”, is a small single-shaft turbojet engine. Weighing between 300 and 500 pounds, it is one of GE's most successful and longest-serving military jet engines. The J85 was originally designed in 1954 to power a large decoy missile, the McDonnell ADM-20 Quail, which was to be released from a B-52 bomber. The engine was designed to produce 2,950 pounds of non-afterburning thrust.
The J85 has an eight-stage axial-flow compressor powered by two turbine stages and is capable of generating up to 2,100 lbf of dry thrust, or more with an afterburner. At full throttle at sea level, the engine consumes approximately 400 US gallons of fuel per hour without an afterburner. Military versions of the engine produce up to 3,500 lbf of thrust dry, while afterburning variants can reach up to 5,000 lbf.
The J85 has been used to power a variety of aircraft, including the Northrop T-38 Talon, the Northrop F-5, and the Cessna A-37 Dragonfly light attack aircraft. More recently, the J85 has powered the Scaled Composites White Knight aircraft and the carrier for the Scaled Composites SpaceShipOne spacecraft. The United States Air Force plans to continue using the J85 in aircraft through 2040, with NASA and other operators expected to operate J85-powered T-38s beyond that.
The J85 engine has also undergone several modifications and upgrades over the years to extend its service life. For example, the J85-5 engine modification includes a redesigned compressor rotor and stator assembly, an improved HPT, and a new afterburner liner. Additionally, the J85-13 is a single-spool turbojet engine with an eight-stage axial-flow compressor and a two-stage turbine, while the J85-17A is a single-shaft turbojet engine that produces up to 2,450 lbf of thrust dry.
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Frequently asked questions
The General Electric J85 is a small single-shaft turbojet engine. The fuel consumption of a J85 engine depends on various factors, including the additional equipment, specific model, and flight conditions. The J85 engine used in the Orenda-manufactured Canadair CF-116 has a specific fuel consumption of 1.24 lb/(lbf⋅h) or 35 g/(kN⋅s) of dry thrust and 2.13 lb/(lbf⋅h) or 60 g/(kN⋅s) of afterburner thrust.
Fuel consumption is influenced by a complex combination of factors, including engine technology, mission requirements, speed, and altitude. For example, flying at supersonic speeds can result in higher fuel consumption due to increased air resistance, while flying at high altitudes can reduce air resistance and fuel consumption.
The fuel consumption of the J85 engine varies depending on the specific model and additional equipment. When compared to other jet engines, such as the F-16 Fighting Falcon and the F-22 Raptor, the J85 engine's fuel consumption falls within a similar range. The F-16 consumes approximately 3,800 liters of fuel per hour, while the F-22 can exceed 8,000 liters per hour due to its vectored thrust and stealth technology.
