Lyulka AL-21
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The Lyulka AL-21 is an axial flow turbojet engine created by the Soviet Design Bureau named for its chief designer Arkhip Lyulka.
Design and development
The AL-21 is closely similar in technology to the General Electric J79 first flown in 1955, which was the first engine for supersonic flight, using a variable stator.<ref>Aircraft Propulsion and Gas Turbine Engines By Ahmed F. El-Sayed p. 16</ref>
It is generally described as being in the "third generation" of Soviet gas turbine engines which are characterized by high thrust-to-weight ratios and the use of turbine air cooling.<ref>Sosounov, V.A. (1990). The Development of Aircraft Power Plant Construction in the USSR and the 60th Anniversary of CIAM. AlAA/ASME/SAE/ASEE 26th Joint Propulsion Conference, July 16–18, 1990. Orlando, Florida. AIAA-90-2761.</ref>
The AL-21 entered service in the early 1960s. Later designed the AL-21F3, it was used in the Sukhoi Su-17, Sukhoi Su-24, Ground-attack variant Mikoyan-Gurevich MiG-23, and Sukhoi T-10 (Sukhoi Su-27 prototype).