Saturn AL-31

AL-31
Saturn AL-31 FN turbofan engine
Type	Turbofan
National origin	USSR/Russia
Manufacturer	Lyulka (now NPO Saturn), UMPO, NPC Salyut, HAL
Major applications	Sukhoi Su-27 Sukhoi Su-30 Sukhoi Su-35 Sukhoi Su-57 Shenyang J-11 Chengdu J-10 Chengdu J-20 Sukhoi S-70B Okhotnik-B

The Saturn AL-31 is a family of axial flow turbofan engines, developed by the Lyulka, now NPO Saturn, in the Soviet Union/Russia, originally for the Sukhoi Su-27 long range air superiority fighter. It currently powers most of the Su-27 family and the Chengdu J-10 multirole jet fighter. Assembly of the engine is also performed under license in India. Highly improved variants power the fifth-generation Sukhoi Su-57 and Chengdu J-20.

Development and design[]

The design of the AL-31 turbofan began in the 1970s under the designation izdeliye 99 by the Lyulka design bureau. With an emphasis on greater fuel efficiency over turbojets for longer range, the turbofan engine was intended to power the heavy PFI (Russian: ПФИ, short for: перспективного фронтового истребителя, lit. 'Promising Frontline Fighter'), which was being developed by Sukhoi as the T-10. It was designed to produce 7.8 tonnes (76.2 kN, 17,100 lbf) of thrust dry and 12.5 tonnes (122.6 kN, 27,600 lbf) of thrust in afterburner. The chief designer was Arkhip M. Lyulka, and after his death, Victor M. Chepkin. As the AL-31 was not yet ready for the first two T-10 prototypes in 1977, they were initially powered by modified AL-21F3 turbojet engines. The third prototype would be the first to install the AL-31. The T-10 design would be heavily revised into the T-10S, with T-10-7 being the first prototype of the improved design; the aircraft's aerodynamic refinements from changes in the outer shaping and packaging also resulted in the AL-31 gearbox changing to a top-mounted position. State tests of the AL-31 were completed in 1985, and the T-10 entering Soviet air services as the Su-27. The engine is manufactured at Ufa-based UMPO and Moscow-based Salyut.^[1][2]

After the collapse of the Soviet Union, design bureau and production plant distinctions gradually faded, and Lyulka-Saturn, now NPO Saturn, became aligned with UMPO while Salyut became an independent entity. Both Saturn and Salyut would make their own developments for the AL-31 family. Salyut also supplies AL-31 variants to fighters operated by the People's Republic of China. The J-10 uses the AL-31FN while the J-20 uses the AL-31FM2 as an interim engine until the domestic WS-15 is ready.^[3] This would result in serious disputes between Saturn and Salyut over intellectual property rights and royalties over AL-31 sales to China.^[2]

Design[]

The base model AL-31F is a two-shaft axial-flow turbofan. The engine has a four-stage low-pressure compressor and a nine-stage high-pressure compressor, both driven by single stage turbines. Overall pressure ratio is 23, and the turbine inlet temperature is 1,392 °C; the turbine blades incorporate air film cooling. The engine is controlled by the analogue KRD-99 unit, and can tolerate severely distorted air flow from the intake. The AL-31 has a modular design to facilitate maintenance and overhaul. In the twin-engine Su-27, left and right engines are interchangeable. Initially, the Mean Time Between Overhaul (MTBO) of the engine was only 100 hours, short of the required 300 hours. Improvements has increased the figure, and the MTBO for the AL-31F series 42 is 1000 hours with a full-life of 3000 hours.^[2]

According to Saturn's Victor Mihailovich Chepkin, chief designer of the 117 and 117S engines, the Chinese WS-10 was developed with the aid of the AL-31's maintenance technical documentation;^[4] this was recently confirmed by AVIC.^[5]

Further development[]

The AL-37FU and AL-31FP variants have thrust vectoring. The AL-37FU was an experimental thrust vectoring variant for a modified Su-27M, later designated Su-37, and was uprated to 32,000 lbf (142.2 kN) of thrust. After the engines reached the end of their service lives, the sole Su-37 was equipped with the normal AL-31F until it crashed in December 2002. The research on thrust vectoring would be applied to the production AL-31FP used in the Su-30MKI export version of the Su-30 for India & Sukhoi Su-30MKM for Malaysia. This engine has the same thrust as the base AL-31F, but can deflect its nozzle to a maximum of ±15° at a rate of 30°/sec. The vectoring nozzle is used primarily in the pitch plane, but the canting of the vectoring axes allow differential vectoring to produce roll and yaw moments as well. AL-31FP is built in India by HAL at the Koraput facility under a deep technology transfer agreement.

AL-31F series 42 (AL-31FM1) at Russian Defense Ministry Innovation Day 2013

The AL-31FN variant was developed to power the Chengdu J-10, with key differences including slightly more thrust and gearbox relocated from the top to the bottom of the engine. Later J-10 variants and production lots were equipped with the improved AL-31FN series 3. In addition to selling AL-31FN to China, Salyut developed improved variants of the AL-31F with increased thrust and reliability. The AL-31FM1, also referred to as the AL-31F series 42, had improved MTBO and thrust increased to 29,800 pounds-force (132.4 kN). Subsequent developments by Salyut include the AL-31FM2 with a larger diameter fan and increased turbine inlet temperature, and a proposed AL-31FM3 with additional fan and core improvements. Initial production Chengdu J-20 are powered by the AL-31FM2.^[2]

AL-41F1 (117)[]

AL-41F1 for fifth generation Sukhoi PAK FA (The international aerospace salon MAKS-2011)

Due to the decline of the MiG 1.42/1.44 MFI fifth-generation fighter program in the 1990s, the Russian Defence Ministry initiated the PAK FA program for a more affordable next-generation multirole fighter, with the competition announced in 2001. As the designs would be smaller than the MFI, the original Lyulka-Saturn AL-41F design was too large. Instead, a highly improved AL-31F derivative designated the izdeliye 117, with some application of technology from the AL-41F, was contracted by Sukhoi specifically for its T-50 design, which would eventually enter service as the Su-57. The izdeliye 117, or AL-41F1, began development in 2004 and has increased fan diameter, new high- and low-pressure turbines, provisions for thrust-vectoring nozzles similar to the AL-31FP, and a digital control system (FADEC) integrated into the aircraft's flight controls. Though the specifics remain classified, the engine's thrust was increased by 24.5 kN (5,500 lbf) over the AL-31 while the engine weight growth was reduced by 150 kg (330 lb). The AL-41F1 produces 88.3 kN (19,900 lbf) of thrust dry, 142.2 kN (32,000 lbf) in afterburner, and 147.1 kN (33,100 lbf) in an emergency, with a dry weight of approximately 1,600 kg (3,500 lb) and thrust-to-weight ratio of 9.3:1.^[6][7] Like the AL-31F, the AL-41F1 has 4 low-pressure compressor (fan) and 9 high-pressure compressor stages.^[8] According to Sukhoi director Mikhail Pogosyan, the AL-41F1 meets the Russian Air Force requirements and will be installed in production Su-57 fighter which will be supplied to the Russian Air Force and prospective foreign clients.^[7] As the Su-57 is meant to be the basis for a family of stealth combat aircraft, future improved variants are planned to be powered by the Saturn izdeliye 30, a new design.

AL-41F1S (117S)[]

To spread out development risks and associated costs with the fifth-generation PAK FA program, Sukhoi applied some of the technology, including the propulsion system, into a highly upgraded Su-27 variant, designated T-10BM (popularly called the Su-35BM), before being designated just as the Su-35. The aircraft's powerplant, the izdeliye 117S, or AL-41F1S, is a slightly simplified derivative of the AL-41F1 from the Su-57, with the key difference being the separate engine control system of the AL-41F1S, and intended for export.^[9] The engine produces 86.3 kN (19,400 lbf) of thrust dry, 137.3 kN (30,900 lbf) in afterburner, and 142.2 kN (32,000 lbf) in an emergency.^[10] The AL-41F1S fan diameter of 932 mm (36.7 in) is 3% greater than the AL-31's 905 mm (35.6 in). This engine has an assigned life of 4,000 hours and an MTBO of 1,000 hours.^[11] The first flight of this engine was completed in an Su-35BM on 20 February 2008.^[12] On 9 August 2010, Ufa-based company UMPO started supplying 117S engines (AL-41F1S) intended for Su-35S fighters.^[13]

Variants[]

Specifications[]

AL-31F[]

Data from Gordon,^[24] Rosoboronexport,^[25] United Engine Corporation^[26]

General characteristics

• Type: Two-shaft afterburning turbofan
• Length: 4,945 mm (194.7 in)
• Diameter:
  
  • 905 mm (35.6 in) inlet;
  • 1,280 mm (50 in) maximum external
• Dry weight: 1,520 kg (3,350 lb)

Components

• Compressor: 4 fan and 9 HP compressor stages
• Combustors: Annular
• Turbine: 2 single-staged turbines

Performance

• Maximum thrust:
  
  • 76.2 kN (17,100 lb_f) dry thrust
  • 122.6 kN (27,600 lb_f) with afterburner
• Overall pressure ratio: 23:1
• Bypass ratio: 0.56:1
• Air mass flow: 112 kg/s (250 lb/s)
• Turbine inlet temperature: 1,665 K (2,537 °F; 1,392 °C)
• Specific fuel consumption:
  
  • Dry thrust: 22.1 g/kN/s (0.78 lb/lbf/h)
  • With afterburner: 55.5 g/kN/s (1.96 lb/lbf/h)
• Thrust-to-weight ratio: 4.93 (dry), 8.22 (afterburning)

AL-41F-1S (117S)[]

Data from Rosobornexport^[27]

General characteristics

• Type: Two-shaft afterburning turbofan
• Length: 194.6 in (494.2 cm)
• Diameter: 36.7 in (93.2 cm) inlet
• Dry weight: 3,536 lb (1,604 kg)

Components

• Compressor: Axial, 4 stage fan, 9 stage compressor
• Combustors: Annular
• Turbine: 2 single stage turbines

Performance

• Maximum thrust:
  
  • 19,400 lbf (86.3 kN) dry
  • 30,900 lbf (137.3 kN) with afterburner
  • 32,000 lbf (142.2 kN) emergency thrust
• Turbine inlet temperature: 2,681 °F; 1,472 °C (1,745 K),
• Fuel consumption:
  
  • 15,020 lb/h (6,813 kg/h) dry
  • 55,050 lb/h (24,969 kg/h) with afterburner
• Specific fuel consumption:
  
  • 0.790 lb/lbf/h (22.37 g/kN/s) dry
  • 1.819 lb/lbf/h (51.53 g/kN/s) with afterburner
• Thrust-to-weight ratio: 5.49 (dry), 8.75 with afterburner, 9.04 with emergency thrust

See also[]

Comparable engines

• General Electric F110
• Pratt & Whitney F100
• Klimov RD-33
• Shenyang WS-10
• Soloviev D-30

Related lists

• List of aircraft engines

References[]

Notes

External links[]

Wikimedia Commons has media related to Saturn AL-31.

• Russian Military Analysis - AL-31 F aircraft turbofan engine
• AL-31F on LeteckeMotory.cz (cs,en)
• AL-41F1A (117S) on LeteckeMotory.cz (cs,en)