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General Electric J79

General Electric Aviation · Aircraft Engine · USA · Early Jet (1946–1969)

General Electric J79 — Aircraft Engine
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The General Electric J79 is an axial-flow turbojet that became the defining American supersonic-fighter engine of the Cold War. First run in 1954 and entering service in 1955, it powered Mach 2-class airframes for more than three decades and was built in greater numbers than any other Western supersonic turbojet. More than 17,000 J79s were produced, by General Electric in the United States and under licence by Allison, IHI in Japan, MTU in West Germany, FIAT in Italy, and Bet Shemesh Engines in Israel.

The engine introduced two features that became standard on later high-performance turbojets: variable inlet guide vanes and variable stator vanes on the first six compressor stages. By rotating these blades in flight, the J79 could maintain efficient airflow from low subsonic speeds to Mach 2, eliminating the surge problems that crippled earlier single-spool turbojets. The 17-stage compressor delivered a pressure ratio of around 12:1, and the three-stage turbine drove it through a single shaft. Dry thrust ran 10,000-11,900 lbf depending on dash number, and afterburner thrust climbed to 17,900 lbf on the J79-GE-17.

Service applications read like a roll-call of Mach 2 hardware. The F-104 Starfighter used the J79-GE-7 and -19 to set a sequence of world speed records and serve in seventeen air forces. The F-4 Phantom II ran twin J79-GE-17s and became the most-produced Western supersonic fighter, with the engine smoking visibly enough at military power that pilots used afterburner on approach simply to clear the trail. The B-58 Hustler carried four J79-GE-5s for Mach 2 nuclear strike. The A-5 Vigilante used the J79-GE-8 for U.S. Navy carrier-based supersonic strike and reconnaissance.

License production in Israel kept the J79 in front-line service into the 1990s. Bet Shemesh built the J79-J1E to power the IAI Kfir, a Mirage-derived multirole fighter that flew with the Israeli Air Force, the Colombian Air Force, the Ecuadorian Air Force, the Sri Lankan Air Force, and was leased to the U.S. Navy and U.S. Marine Corps as the F-21A adversary aircraft. A marinised LM1500 industrial variant powered hydrofoils, oil-rig generators, and gas pipeline pumping stations into the 2000s.

By the late 1970s the J79 was being replaced in U.S. front-line service by the Pratt & Whitney F100 and General Electric F110 turbofans, which offered better fuel economy at subsonic cruise and far higher thrust-to-weight ratios. Production ended in 1988, though overhaul and parts support continued at GE's Lynn, Massachusetts plant for export Phantoms and Kfirs through the 2010s. The engine's variable-stator concept survives in every modern military turbofan in service today.

For Kids — a shorter, friendlier version

The General Electric J79 is a jet engine made in America. It first ran in 1954 and went into service in 1955. It helped power some of the fastest planes of its time. It could push aircraft to speeds of Mach 2, which is twice the speed of sound!

The J79 powered famous planes like the F-104 Starfighter, the F-4 Phantom II, and the B-58 bomber. It was also used by the Israeli Kfir fighter jet. Many countries built this engine, including Japan, West Germany, Italy, and Israel.

One cool thing about the J79 is how it controls airflow. It has special blades that can rotate while the plane is flying. This helped the engine work well at both slow and very fast speeds. Earlier engines had big problems with this, but the J79 fixed them.

The J79 was built more than 17,000 times. That is more than any other Western supersonic jet engine. It is smaller than a school bus but could produce up to 17,900 pounds of pushing force with its afterburner on. An afterburner gives the engine a huge boost of extra power.

The J79 stayed in use for more than thirty years. It was one of the most important engines of the Cold War era. General Electric made a design that truly changed how fast planes could fly.

Fun Facts

  • The J79 engine first ran way back in 1954, the same year many of your grandparents were born!
  • More than 17,000 J79 engines were built, making it the most produced Western supersonic jet engine ever.
  • The J79 could push planes to Mach 2, which means twice the speed of sound — faster than a rifle bullet!
  • Six countries or companies built the J79, including factories in Japan, Italy, West Germany, and Israel.
  • The J79 has 17 compressor stages inside it, all spinning at incredible speed to push air through the engine.
  • With its afterburner on, the J79 produced 17,900 pounds of thrust — like a giant invisible push from behind!
  • The J79 powered the F-4 Phantom II, one of the most famous fighter jets in history.
  • Special rotating blades inside the J79 let it work well at both slow speeds and twice the speed of sound.

Kids’ Questions

What makes the J79 engine special?

The J79 has special blades inside that can rotate while the plane flies. This helped it work well at slow speeds and at Mach 2. Earlier jet engines had big problems keeping steady airflow at high speeds. The J79 fixed that problem with its clever design.

What is an afterburner and why is it used?

An afterburner is a system that sprays extra fuel into the engine's exhaust to create a huge burst of power. It makes the engine much stronger for a short time. The J79's afterburner boosted its thrust to 17,900 pounds. Pilots use it when they need extra speed fast.

Which planes used the J79 engine?

The J79 powered several famous planes. These include the F-104 Starfighter, the F-4 Phantom II, the B-58 bomber, and the Israeli Kfir jet. All of these planes could fly at Mach 2, which is twice the speed of sound.

How many J79 engines were ever made?

More than 17,000 J79 engines were built in total. General Electric made them in America, but factories in Japan, West Germany, Italy, and Israel also built them. That is a huge number for a supersonic jet engine!

Variants

J79-GE-3
Initial production variant from 1955, 14,800 lbf with afterburner. Used on early F-104A Starfighters.
J79-GE-5
Four-engine installation on the B-58 Hustler Mach 2 bomber. 15,600 lbf with afterburner.
J79-GE-8
U.S. Navy carrier-deck variant for the A-5 Vigilante. 16,950 lbf with afterburner.
J79-GE-17
Most-produced variant. Powered the F-4E Phantom II at 17,900 lbf with afterburner. Used on twin-engine fighter installations through the 1970s.
J79-GE-19
Final USAF production dash number for the F-104S Italian Starfighter. 17,900 lbf, improved hot section.
J79-J1E (Bet Shemesh)
Israeli licence-built variant for the IAI Kfir. Production continued in Israel into the 1990s for Kfir upgrades and exports.
LM1500 (industrial)
Marinised single-spool variant for hydrofoils, oil platform power generation, and gas pipeline pumping. Spawned the marine LM2500 lineage.

Notable Operators

McDonnell Douglas F-4 Phantom II
Twin J79-GE-17 installation produced more than 5,000 airframes for the U.S. Air Force, U.S. Navy, U.S. Marine Corps, and eleven foreign air forces. The most-produced Western supersonic fighter.
Lockheed F-104 Starfighter
Single-engine Mach 2 interceptor flown by seventeen air forces. The J79 paired with the F-104's tiny trapezoidal wing produced a fighter with extreme climb performance and an unforgiving low-speed handling reputation.
Convair B-58 Hustler
Four-engine supersonic nuclear bomber, the first to sustain Mach 2 in level flight. Served in U.S. Air Force SAC 1960-1970.
IAI Kfir
Israeli Mirage derivative powered by the licence-built J79-J1E. Flown by Israel, Colombia, Ecuador, Sri Lanka, and leased to the U.S. Navy and U.S. Marine Corps as the F-21A adversary trainer.
North American A-5 Vigilante
Twin-engine U.S. Navy supersonic carrier-based bomber and reconnaissance aircraft, in service 1961-1979.

Frequently Asked Questions

Why was the J79 so widely used?

The J79 hit a sweet spot the U.S. industry needed in 1955: 10,000-class thrust, Mach 2 cruise, and a variable-stator compressor that worked reliably across the full speed range. No other Western engine combined those traits at the time. Once the F-104, F-4, and B-58 standardised on the J79, second-generation U.S. fighters were locked into it through commonality with maintenance and spare-parts pipelines. More than 17,000 units were built across thirty-three years of production (GE Aerospace J79 page).

What made the F-4 Phantom II smoke so heavily?

The J79-GE-17's combustor ran rich at military power, producing visible unburned hydrocarbons in the exhaust. Pilots routinely lit the afterburner on approach because the higher combustor temperature burned the soot off and eliminated the smoke trail that gave Phantoms away at 20 nautical miles. The smokeless combustor on later J79-GE-17C/E and -19 dash numbers fixed the problem, but earlier airframes carried the smoking reputation for the rest of their service lives.

How did the J79 compare to the Pratt & Whitney J75?

The J75 was bigger and produced more thrust at 24,500 lbf with afterburner, but it weighed more, drank more fuel, and never matched the J79's Mach 2 efficiency. The J75 found its niche on the F-105 and F-106; the J79 dominated the Mach 2 lightweight-fighter market. The J79 was also a single-spool design with variable stators, while the J75 used a two-spool architecture without variable geometry.

Are any J79 engines still flying?

Yes, into 2026. IAI Kfir upgrades fly with the Colombian Air Force (Kfir C10) and the Sri Lankan Air Force, and Iranian F-4E Phantoms remain in service with the Islamic Republic of Iran Air Force on smuggled and indigenously-overhauled J79s. The U.S. Navy's adversary leases of Kfirs ran through 1989; private contractors operating Kfirs as adversary aircraft for the U.S. Navy and U.S. Marine Corps still fly them today.

What replaced the J79?

Front-line USAF service ended when the F-15 Eagle and F-16 Fighting Falcon entered service with the Pratt & Whitney F100 turbofan. Later F-16s switched to the General Electric F110, which was a direct descendant of the F101 bomber engine and produced 28,000 lbf with afterburner in a similar-diameter package. The turbofan architecture cut subsonic cruise fuel burn by around 30 percent compared to the J79, decisively ending the front-line turbojet era for fighters.

What were variable stators and why did they matter?

Variable stator vanes are stationary blades in the compressor that pivot to change the angle at which air strikes the next rotating stage. By matching the blade angle to flight speed and throttle setting, the J79 avoided the compressor stalls that plagued earlier single-spool turbojets at low speeds and high throttle. The concept was invented by GE's Gerhard Neumann and remains standard practice on every modern turbofan, from the F135 to the CFM56.

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