Douglas Barrie/LONDON

SUKHOI'S LATEST pre-production Su-35 has been fitted with thrust-vectoring nozzles, and it is believed to be undertaking flight tests at the Zhukovsky flight-test research centre near Moscow.

First pictures of the advanced Flanker derivative show two axisymmetric nozzles fitted to the aircraft. Senior Sukhoi designers have claimed that the Su-35 will enter service with thrust-vectoring control (TVC) as standard.

While the round nozzle appears to be axisymmetric, the aircraft retains the full-tail sting of previous Su-35, making it likely that the TVC is only available in the pitch plane. Nozzle movement in the yaw plane would seriously risk damaging the tail sting.

TVC is being pursued by Russia and the West as part of the quest, for a super- manoeuvrable fighter aircraft. The USA has several programmes under way such as the Pratt & Whitney pitch/yaw balanced-beam nozzle and the Multi-Axis Thrust-Vectoring (MATV) programme.

Unlike the MATV, the Su-35 TVC nozzle appears to retain the usual actuators for a convergent/divergent nozzle, coupled with the actuators necessary for pitch movement. This probably means that the TVC unit imposes a weight penalty. Earlier pictures of a TVC system, shown on a test rig, showed only slow nozzle movement.

There is a question as to whether the TVC nozzles can move effectively at the same speed as the Su-35 tail plane. This is desirable for optimum super-manoeuvrability.

Previously, Sukhoi had shown a box-like nozzle fitted to a Su-27, dubbed the Su-27UBL. This aircraft had been seen in 1990.

Some Sukhoi officials say, that this nozzle was intended to be used to explore, reducing a supersonic commercial aircraft's sonic footprint, but others contradict this.

The nozzle on this aircraft is unlikely, given its size, to be associated with the Su-35, and may have been intended for a larger aircraft.

Source: Flight International