T-10 Su-27 FLANKER-A Prototype
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 program 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, it was ae 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 on 19 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 20 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.
