Reading level:

Saturn AL-31F

NPO Saturn / UEC-Saturn · Aircraft Engine · Russia · Cold War (1970–1991)

Saturn AL-31F — Aircraft Engine
Open in interactive gallery →

The Saturn AL-31F is a Soviet/Russian afterburning low-bypass turbofan developed by the Lyulka design bureau (now NPO Saturn / UEC-Saturn) in the late 1970s and early 1980s as the powerplant for the Sukhoi Su-27 long-range air-superiority fighter. Designed to compete head-to-head with the American Pratt & Whitney F100 and General Electric F110, the AL-31F entered service in 1985 and went on to power the entire Sukhoi Flanker family for the next four decades.

The AL-31F is a twin-spool axial-flow turbofan with a four-stage low-pressure compressor, nine-stage high-pressure compressor, annular combustor, and single-stage HP and LP turbines. Sea-level static thrust is around 17,000 lbf dry and 27,560 lbf with full afterburner, in the same class as the F100-PW-220. The engine is noted for its tolerance of high angles of attack and rapid throttle response, qualities Sukhoi exploited in the cobra and other post-stall manoeuvres flown at airshows by the Su-27 family.

Application across the Sukhoi line is extensive. Two AL-31Fs power each Su-27, Su-30, Su-33 naval fighter, and Su-34 strike aircraft, plus the early production blocks of the Su-35 before that aircraft transitioned to the AL-41F1S. The AL-31FP thrust-vectoring derivative on Su-30MKI and Su-35 uses round nozzles that swivel in pitch and limited yaw, giving the airframe super-manoeuvrability without the weight penalty of a 2D paddle nozzle.

Export sales have been heavy. Hindustan Aeronautics builds the AL-31FP under licence in Koraput, India, for the Indian Air Force Su-30MKI fleet. China imported large numbers of AL-31F and AL-31FN engines through the 1990s and 2000s to power early Chengdu J-10 single-engine fighters and Shenyang J-11 Flanker copies, as well as the J-15 carrier fighter and J-16 strike fighter, before transitioning to the indigenous WS-10 Taihang.

More than 5,000 AL-31 family engines have been built, making it the most-produced Russian fighter engine of the post-Cold-War era. Production continues at UEC-Saturn in Rybinsk and at the UMPO plant in Ufa. The improved AL-41F1 derivative powers the Su-57 in its first-stage configuration, while the long-term Izdeliye 30 (AL-51F) is the planned second-stage engine for that aircraft.

For Kids — a shorter, friendlier version

The Saturn AL-31F is a powerful jet engine made in Russia. Engineers began designing it in the late 1970s. It first flew on planes in 1985. The engine was built to power the Sukhoi Su-27 fighter jet.

This engine pushes out about 27,560 pounds of force with its afterburner on. An afterburner sprays extra fuel into hot exhaust gas to make the jet go even faster. That is a huge amount of push for one engine. Each Su-27 uses two of these engines together.

The AL-31F is smaller than a school bus but incredibly strong. It works well even when a pilot tilts the plane at a very steep angle. Fighter pilots use this to do special moves called the cobra at air shows. The engine responds fast when pilots push or pull the throttle.

Many jets use this engine. The Su-27, Su-30, Su-33, Su-34, and Su-35 all run on it. Chinese jets like the J-10 and J-15 also use versions of it. More than 5,000 of these engines have been built so far.

Fun Facts

  • The AL-31F first went into service in 1985 and is still used today.
  • Each AL-31F pushes with over 27,000 pounds of force when the afterburner is on.
  • The Su-27 carries two AL-31F engines, giving it twice the push.
  • Pilots use this engine's fast response to do amazing air show moves called the cobra.
  • Over 5,000 AL-31F engines have been built since 1985.
  • The engine was designed to compete with the best American jet engines of its time.
  • Chinese jets like the J-15 also fly using versions of the AL-31F.
  • The AL-31F is heavier than a family car but fits inside a fighter jet.

Kids’ Questions

What does an afterburner do?

An afterburner sprays extra fuel into the hot gases leaving the engine. This makes a big burst of extra thrust. It helps fighter jets go much faster in a hurry.

Which planes use the AL-31F engine?

Many Russian jets use it, like the Su-27, Su-30, Su-33, Su-34, and Su-35. Some Chinese jets like the J-10, J-11, J-15, and J-16 also use it. It is a very popular engine family.

What is the cobra move that Su-27 pilots do?

The cobra is a special flying trick where the pilot points the jet's nose almost straight up for a moment. The AL-31F helps make this possible because it works well at steep angles. Crowds love watching it at air shows.

Variants

AL-31F (baseline)
Production engine for the Su-27, Su-27UB, Su-30, Su-33, and Su-34. 17,000 lbf dry / 27,560 lbf reheat.
AL-31FP (thrust-vectoring)
Round-nozzle thrust-vectoring derivative for the Su-30MKI (Indian Air Force) and Su-30MKM (Malaysia). Nozzles deflect in pitch and limited yaw. Licence-built by HAL Koraput in India.
AL-31FN (single-engine fighter)
Export variant with bottom-mounted accessory gearbox for the single-engine Chengdu J-10. AL-31FN Series 3 raised reheat thrust to around 30,000 lbf.
AL-31F M1 / M2 (Russian upgrade)
Russian Air Force update programme with redesigned fan and improved hot-section materials, raising reheat thrust to roughly 29,500-30,800 lbf and TBO to 1,000 hours.
Izdeliye 117S (AL-41F1S)
Heavily reworked AL-31 derivative used as the production engine for the Su-35S. Higher mass flow, FADEC, and full 3D thrust vectoring.

Notable Operators

Sukhoi Flanker family (Su-27/30/33/34/35)
Two AL-31Fs per airframe across the Su-27, Su-30, Su-33, and Su-34; early Su-35 blocks before transition to AL-41F1S. Russian Aerospace Forces, Russian Naval Aviation, and 15+ export customers including India, Vietnam, Algeria, Venezuela, and Indonesia.
Chinese Flanker derivatives and J-10
Early Shenyang J-11 Flanker copies, J-15 carrier fighter, J-16 strike fighter, and early J-10 blocks. China imported several hundred AL-31F/FN engines through the 1990s-2010s before transitioning to the indigenous WS-10 Taihang.
Indian Air Force (HAL licence build)
Hindustan Aeronautics builds the AL-31FP under licence at Koraput for the Su-30MKI fleet of around 270 aircraft, the largest single Flanker operator in the world.

Frequently Asked Questions

How does the AL-31F compare to the F100 and F110?

The AL-31F sits in the same 27,000-29,000 lbf reheat class as the F100-PW-220 and early F110-GE-100. Russian designers prioritised tolerance of high angles of attack and rapid throttle response over fuel efficiency, which is why the Su-27 family can fly post-stall manoeuvres like the Pugachev cobra. Specific fuel consumption is higher than contemporary American engines, reflecting the older core technology base.

What is the AL-31FP and which aircraft use it?

The AL-31FP is the round-nozzle thrust-vectoring derivative. Each nozzle swivels in pitch (and to a limited extent yaw), giving the airframe pitch authority below stall speed. Two AL-31FPs power the Indian Air Force Su-30MKI and the Royal Malaysian Air Force Su-30MKM. Russia later moved to a full 3D-vectoring derivative in the AL-41F1S for the Su-35S.

Why did China import the AL-31F instead of using a domestic engine?

When China bought the Su-27 in 1992, it had no engine in the 27,000 lbf class. Imported AL-31Fs powered early J-11 Flanker copies and AL-31FN versions powered the J-10. China continued to buy AL-31s through the 2010s as a hedge while the indigenous WS-10 Taihang matured. By the mid-2020s most new J-10C and J-16 aircraft used the WS-10, with AL-31s still in the older fleet.

How many AL-31s have been built?

More than 5,000 across all variants, making it the most-produced Russian fighter engine of the post-Cold-War era (UEC official). Production continues at the UEC-Saturn plant in Rybinsk and at UMPO in Ufa, supporting both Russian Aerospace Forces orders and export contracts.

Is the AL-31F still in production?

Yes. UEC-Saturn and UMPO continue to build new-production AL-31F M1, M2, and FN Series 3 engines for the Russian Aerospace Forces Flanker fleet, for HAL Koraput licence assembly, and for export Su-30 customers. The derivative AL-41F1 and AL-41F1S also remain in series production for the Su-57 stage-1 configuration and the Su-35S.

What replaces the AL-31F on the Su-57?

The first production block of the Su-57 uses the Saturn AL-41F1 (Izdeliye 117), a 32,000+ lbf derivative of the AL-31. The long-term second-stage engine is the clean-sheet Izdeliye 30 (also called AL-51F), which raises thrust further and adds true supercruise. First flight of an Su-57 with Izdeliye 30 took place in 2017; series production started later in the decade.

Sources

See Also