RUSSIAN ENGINE manufacturer Lyulka Saturn has unveiled a heavily modified variant of its AL-31F powerplant, which has been fitted with pitch-only thrust vectoring nozzles, and redesignated the AL-37FU.
The new engine is being test-flown on a Sukoi Su-27M (Su-35), with around a dozen test flights having been carried out in the past two months from the Gromov flight-test research institute at Zhukovsky.
Sukoi has previously suggested that the Su-27M would have thrust-vector control (TVC) systems in the pitch and the yaw axes, but Victor Chepkin, general designer and president of Lyulka Saturn, says that the Su-27M TVC operates only in the pitch plane. He says that Lyulka Saturn has a pitch/yaw nozzle "in its pocket", however, although this is not believed to be for the Su-27M.
Chepkin cites the difficulty of integrating a TVC system covering the pitch and yaw planes as one reason why it is not being implemented on the Su-27M. The aircraft's tail-sting would also inhibit nozzle movement severely in the yaw axis.
The test aircraft, which has a sidestick rather than a conventional control stick, is believed to be the first Su-27M to be equipped with a digital flight-control system (FCS). Anatoly Andreyev, a senior vice-president with the manufacturer, claims that the TVC is integrated with the FCS and, despite having had only a dozen test flights, the vectoring nozzles have already been tested. The nozzles are claimed to move +/- 20¡.
It remains unclear whether series-production models of the Su-27M will be fitted with TVC. There is no timetable yet for the TVC-equipped Su-27M prototype to be transferred to the Russian air force for tests.
Source: Flight International