Lyulka Saturn has developed a thrust-vectoring version of the AL-31F engine that powers the Sukhoi Su-27. Designated AL-37F, a pair of the power plants have been fitted to a modified Su-27M, dubbed the Su-37 by the design bureau.
The AL-37F has thrust-vectoring in pitch only, although the bureau claims to have also developed a full, two-axis nozzle, which is unsuitable for use on the Su-37 because of the size of the aircraft's tail boom.
The vectoring mechanism is driven by hydraulic actuators, with a compressed air back-up system to return the nozzles to the neutral position. The AL-21 powers the Mikoyan MiG-23 and Sukhoi Su-24 fighters.
Sukhoi's eleventh Su-27M prototype, tail number 711, has been flown for an initial series of 50 flights in which the aircraft's manoeuvre envelope was rapidly expanded to exploit the thrust-vector control. Sukhoi displayed the aircraft for the first time outside Russia at the 1996 Farnborough air show.
The engine design bureau has so far built only three thrust-vector-equipped power plants. The third engine is being used as a static test rig. Although the present thrust-vector design vectors in pitch only, the engine design bureau is also working on a nozzle, which provides both pitch and yaw vectoring.
Source: Flight International
