The Su-27SK single-seat multi-role fighter is an export version of the Su-27 fighter that has been serially produced since 1991.
The fighter is designed to gain air superiority through destroying hostile manned and unmanned aircraft with guided missiles in medium-range engagements and dogfights in individual and group operations; and surface (ground and sea) targets destroying with all types of weapon, first of all with high precision weapon (guided missile and bombs) in all-weather conditions.
The main features of Su-27SK are the following:
high maneuverability provided by high thrust-to-weight ratio, the aircraft perfect aerodynamics, and Fly-by-wire system used for the aircraft longitudinal control;
large flight range due to the aircraft perfect aerodynamics, the power plant high effectiveness, and the inner fuel tanks capacity;
integrated weapon control system consists of two independent complementary channels – radar sighting system and optronic sight system with HMS;
up-to-date navigation system, communication suite, and ECM suite;
an expanded weapons suite (air-to-air guided missiles and bombs, and air-to-surface rockets) with the ordnance mounted externally on 10 hardpoints.
The Su-27SK weapon control system provides for aerial, surface and sea targets designation, tracking and destroying with the air weapon in round-the-clock all-weather conditions. It comprises two main subsystems: radar sighting system and optronic sight system.
Flight and navigation data is indicated on the MFD and HUD, and on the other cockpit instruments as well.
The radar used in Su-27SK is of pulse-Doppler type, it ensures aerial targets searching and tracking in air and against a ground/sea background at 100 km distance. The radar can simultaneously track and prioritize 10 aerial targets, and attack the most dangerous one.
The Su-27SK optronic sighting system comprises Optical-Electronic Location System and HMS (Helmet mounted system). Optical-Electronic Location System is a combination of an infrared search and track system (IRST) and a laser rangefinder/target designator, used to track aerial targets both in the front and rear hemispheres using their infrared signature, and the targets laser ranging.
The Su-27SK aircraft weapons suite includes the built-in GSh-301 30-mm automatic single-barrel high-rate-of-fire cannon with 150 rounds ammunition load; and missiles, rockets and bomb ordnance suspended on 10 hard points located under the wings and fuselage.
Su-27SK can carry up to six R-27R1 (R-27ER1) air-to-air medium-range missiles with semi-active radar homing heads, up to two R-27T1 (R-27ET1) heat-seeking medium-range missiles, and up to six RVV-AE medium-range active radar-homing missiles and six R-73E short-range heat-seeking missiles.
The aircraft weapons suite includes a wide range of different types of weapon to destroy surface (sea) targets. The weapon suite can include bombs of 500, 250 or 100-kg caliber, cluster bombs, incendiary tanks, and the S-8 rockets (in four B-8M1 pods), the S-13 rockets (in four B-13L pods), and the S-25-OFM rockets.
Design work on a 4th-generation fighter, later known as the Su-27, began at the Design Bureau of P.O. Sukhoi on the designers’ initiative under the supervision of O.S. Samoilovich at the end of 1969. The new plane was required to provide effective engagement of the F-15 fighter being developed in the USA under the FX programme from 1966, the Soviet fighter being positioned, the same as its foreign rival, as an “air-superiority” aircraft. In contrast to the USSR’s previous efforts to “catch up” with the Americans, Soviet aircraft designers decided this time to produce an aeroplane in no way inferior, and even superior, to “the adversary”. To achieve this objective, the Design Bureau put quite a few challenging ideas into the configuration under development right from the start, such as placing the engines widely spaced in two nacelles under the fuselage body, and placing the vertical tail unit in between the wings and horizontal tail unit.
At the initial stage, the Design Bureau produced a great number of alternative configuration concepts, including the one based on a conventional solution, with an integral body, modelled on the F-15; but interestingly enough, however, at the end of the day, it was the new concept of airframe configuration that the subsequent design efforts were based upon. Another important feature of the new fighter was to be implementation of the concept of longitudinal static instability, with balancing achieved through use of an electronic distance control system (EDCS). Introduction of this innovation promised a substantial decrease in losses for balancing and a dramatic improvement in the plane’s manoeuvrability in dogfighting.
In the period 1971-72, the aeroplane conceptual design was being developed on a tender basis by the Design Bureaus of A.I. Mikoyan, P.O. Sukhoi, and A.S. Yakovlev. The design of the Su-27 (factory code T-10) had been completed by September 1971 and was submitted for review to Air Forces in February 1972. In 1972, after the aeroplane’s PR for the conceptual design had been updated, it was decided to start parallel development of two fighter versions: a “light” one to be produced by Mikoyan Design Bureau and a “heavy” one, assigned to Sukhoi Design Bureau. Based on input from the military, the Su-27 was redesigned in 1972-73 to meet all the requirements, with the aircraft’s wing area, engine design thrust and integral fuel tankage increased. This resulted in an exceptional range on internal fuel for a Soviet-made fighter. The high performance of the new AL-31F turbofans (“Article 99”) developed by the Design Bureau of A.M. Lyulka, produced specially for the Su-27, were expected to provide the plane with a high thrust-to-weight ratio, and therefore superior characteristics of acceleration, rate of climb and manoeuvrability. The problems caused by inadequacies of Soviet-produced avionics components, unavailable unless heavy and bulky, had to be dealt with by the Design Bureau through introduction of improved design and configuration solutions as well as use of new and promising technologies. In 1973-74, the Design Bureau continued its studies to identify and engineer the plane’s optimal airframe and individual assembly configuration, and the composition of systems, equipment and weapons. The configuration options were tried out with large-scale models in wind tunnel installations at CAHI, SibNIA and MAI facilities. N.S. Chernyakov was appointed the Su-27’s chief designer in 1973. The detailed design work on the aeroplane began in 1975.
The Su-27’s 1975 production configuration featured standard aerodynamic design, with an integrated variable sweep ogive wing configuration, leading-edge root extensions, an all-movable horizontal tail unit mounted on the centre wing section continuation beams, and twin tail fins mounted on engine nacelles at the airframe stern-post. The adjustable engine air intakes with horizontal air brakes placed at the top were put on either side of the plane’s roll axis, and suspended from the centre wing section. This inlet configuration ensured highly stable flow at high angles of attack, which is of vital importance for an aircraft designed for air-combat manoeuvring. The engine nacelles at the tail were an extension of the air intakes. The landing gear featured a standard tricycle type configuration. A major problem inherent in the configuration option chosen was finding a place for the main landing gear bays. Finally, a place for them was found in the “dead air” of the centre wing, under the intake ducts, the gear legs retracting with the wheels turned. The flaps were also used as speed brakes. The airframe was significantly lightened through compact configuration and optimization of the design structure, as well as large-scale use of titanium alloys in the design. The development of the Su-27 was approved by a decree of the government of 19th January 1976 as “a single air-superiority fighter for Air Forces and ADF aviation”. In February 1976, M.P. Simonov was appointed chief designer of the Su-27. By that time, the Design Bureau had already started building the first three T-10 prototypes (two for flight testing and one for structural testing), with brass-board marginal testing of all major systems of the future craft already in progress. Note that for trying out the Su-27 aerodynamics, powerplant, control system, attack and navigation equipment and weapons, the Design Bureau and FRI set up and tested a dozen various flying laboratories, conducting studies on an unprecedented scale in Sukhoi’s practice of engineering systems for a new plane. The engineering documentation produced was passed on to the Komsomolsk-on-Amur plant, which was appointed main contractor for production of the Su-27. In 1977, the facility started to gear up for full-scale manufacture. In October 1977, the Design Bureau’s conceptual design of the Su-27 aeroplane successfully passed critical design review and was approved by an Air Forces committee chaired by 1st Deputy Commander-in-Chief of Air Forces, Air Marshal A.N. Yefimov. The first two flying prototypes of the Su-27 were fitted with AL-21FZAI engines.
Construction of the first prototype T10-1 was completed in April 1977. On 20th May 1977, the design bureau’s chief pilot V.S. Ilyushin performed the first flight. In May 1978, the testing programme was expanded to cover a second prototype, T10-2, and the year after that, in 1979, it received the prototypes T10-3 and T10-4, fitted with operational engines AL-31F («Article 99», with low gearbox). To speed up the trials, it was decided to make available for testing the entire development batch of Su-27s made by the production plant in 1980-81. Later on, the planes were used by the Design Bureau and FRI for testing individual systems. In December 1979, the Su-27 was officially accepted by the military for governmental testing. But it was a different version of aeroplane that was put into series production.
Comprehensive analysis of the performance of the Su-27 performance compared to similar Western models, semi-realistic simulation of air combat and actual data obtained during the first flights of the prototype failed to confirm the expected air-superiority of the Su-27. Such a result was due to a number of reasons, the major ones being underestimation of the actual performance capabilities of the F-15, and on the serious excess weight of the Su-27 through failure to meet the weight restrictions for the systems and equipment design as well as the underperformance of the AL-31F engines revealed during their bench testing. To meet the PR targets and achieve a guaranteed result in the plane’s basic role, on the initiative of Chief Designer M.P. Simonov, and approved by General Designer Ye.A. Ivanov, the Bureau developed a plan of actions to:
– introduce tight control of weight,
– decrease drag,
– increase the lift properties of the wing to adapt it to different flight modes,
– improve the plane’s roll control.
To implement the plan, aerodynamicists and planners of the Design Bureau pooled their efforts to develop a number of specific recommendations on how to redesign the original configuration of the Su-27, viz.:
– adopt a tapered wing design with a leading-edge flap and flaperon,
– move the aircraft accessories box onto the back of the engine, which made it possible to “hide” it in the centre-wing airflow-shadow and reduce the plane’s maximum cross-section,
– adopt a new functional solution for main landing gear retraction based on a slanting hinging axis and a lock to fix the gear leg on the engine housing,
– move the fins from the engine nacelles to the fuselage beams to improve their rigidity and the fin performance.
Taken together, all the modifications were incorporated in the configuration that became known as T-10S (“S” being short for “production” in Russian). General Designer Ye.A. Ivanov made a difficult decision to have the aircraft redesigned. The root of the problem was that the engineering follow-up involved suspending the series production already in progress and initiating a new major process to put the project into production, i.e., failure to meet the production targets.
The Design Bureau’s position was strongly opposed by the management of MAI and the production plant, but it was supported by deputy minister I.S. Silayev. As a result, a decision to this effect was made in January 1978, and the Design Bureau started work on detailed design based on the T-10S configuration. Between 1979 and 1981, the Su-27 project at the Design Bureau was headed by A.A. Kolchin, and since 1981, the aeroplane’s Chief Designer has been A.I. Knyshev.
The first Su-27 prototype in production configuration, T10-7, was accepted for flight testing in the spring of 1981, its first flight performed by V.S. Ilyushin on 20th April 1981. In 1982, the Komsomolsk-on-Amur plant started mass production. The first series Su-27 was flight tested at the plant on 1st June 1982, the plane having been taken off the ground for its first flight by the design bureau’s test pilot A.N. Isakov. Governmental integration tests of the Su-27 were completed in December 1983.
The test results confirmed the extremely high APC of the new aeroplane. When brought together, the modifications produced a synergetic effect on the T-10S: the resulting plane demonstrated superior flight performance, leaving behind all the rivals in its class.
The testing of the Su-27 under a variety of programmes continued for several years longer. The Su-27 was officially put into service by a decree of the government of 23rd August 1990 after all the major faults identified during the tests had been remedied. By that time, Su-27 had been in service for 5 years. The first pilots at combat units to receive the Su-27 in June 1985 were the aviators of the 60th FAR in the Far Eastern MD (Dzemghi). By 1989, Su-27 aeroplanes were in service in 16 combat units of the Air Forces and ADF of the USSR. According to the command personnel and pilots of the transition units, despite the fact that in terms of scope and complexity the systems and weapons the plane was far superior to all aircraft of the previous generation, Su-27 transition training was quite straightforward and problem-free, with the plane proving quite easy to master for average pilots.
The Design Bureau started work to develop a two-seat combat trainer version of the Su-27 in 1976, with conceptual design of the Su-27UB (factory code T-10U) successfully passing critical design review in 1978. The first prototype of the two-seater was made at the Komsomolsk-on-Amur production plant to the design bureau specifications and returned to Moscow for engineering follow-up in the spring of 1984. The first flight of the T10U-1 was performed 7th March by the design bureau’s test pilot N.F. Sadovnikov. Official testing took place between 1985 and 1987. Production of a Su-27UB development batch was set up in Komsomolsk-on-Amur, and in 1985 MAI gave the order for the production of the two-seat trainer to be moved to Irkutsk. The first mass-produced Su-27UB was flight tested at the Irkutsk plant on 10th September 1986 by a crew of test pilots G.Ye. Bulanov and N.N. Ivanov. The combat units received the first production Su-27UB in 1987.
The programme to develop the Su-27 as a new-generation plane was the USSR’s major national defence programme in the ’70s-’80s. Its implementation was financed on a large scale, which had the most favourable effect on the development of many establishments in the national aircraft industry and related areas, making it possible to retrofit many production facilities and introduce a great number of new technologies.
The Su-27 programme set up a large network of subcontractors across the country. Large-scale introduction of leading-edge technologies was the rule for all of the plane’s systems. For example:
– The plane’s powerplant comprises two AL-31F turbofans developed by the Design Bureau of A.M. Lyulka. In terms of specifications and performance, these are new-generation engines with superior weight, thrust and fuel consumption characteristics achieved through a dramatic improvement in compressor gas-dynamic behaviour and operating temperature before the turbine. It was only possible to achieve such characteristics by harnessing promising new materials and technologies: new titanium alloys, heat-resistant steels, single-crystal vanes, special coatings, and other new features;
– For the plane as a whole, it was vitally important to stay within the weight limits so that the Su-27’s various systems had to be extensively reengineered to incorporate new components. For example, it was decided, to meet the specifications for the control system and reduce the size and weight of its assemblies, to incorporate in the plane’s design the USSR’s first mass-produced hydraulic system with operating pressure increased up to 280 kg/cm², and a radically new type of steering linkage, with power and distribution centres separated into individual blocks;
– The Su-27’s avionics were developed based on large-scale introduction of digital processing using an onboard computer and the principle of extensive integration of various systems by function; for instance, the fire control system incorporated, in addition to a target search and track radar channel (multi-purpose onboard radar), an independent information channel, i.e., an optical search and tracking station;
– As part of the goal-oriented retrofitting programme, the Su-27 received a specially developed new-generation guided missile of medium (K-27E) and short (K-73) range.
All the above made it possible to create a combat aircraft capability which can be used to effectively engage the very best foreign-made combat planes. All the subsequent history of the Su-27 series validates this conclusion.
Between 1986 and 1990, using a specially configured prototype aeroplane T10-15, which became known as P-42, the design bureau’s test pilots established 41 IAF-registered world records of rate-of-climb and flight altitude, some of the records being absolute.
In June 1989, the Su-27 and Su-27UB were for the first time shown abroad, at the Le Bourget air show. The design bureau’s test pilots V.G. Pugachov and Ye.I. Frolov demonstrated to the international aviation community the superior manoeuvrability of Sukhoi planes. From that day on, Su-27 type planes have been participating in the most prestigious international aviation events, invariably demonstrating the highest level of achievement in the Russian aircraft industry.
Another proof of the plane’s superior combat performance is the Su-27’s commercial success in the global marketplace. Starting in 1991, the production facilities in Komsomolsk-on-Amur and Irkutsk have been producing export variants of the Su-27: the Su-27SK and Su-27UBK. Models of these types have since 1992 been exported to China, Vietnam, Ethiopia and Indonesia, and Su-27SKs have since 1998 been produced as the F/J-11 in China under licence in accordance with intergovernmental agreement. The first licensed-production plane, assembled in the town of Shenyang, was flight tested on 16th December 1998.
As a baseline design, Su-27 had a high reconfiguration potential, which allowed the Design Bureau to start work on enhanced versions.