Pictured left is the first Sukhoi Su-27M to be fitted with axisymmetric thrust-vectoring-control (TVC) nozzles, during a recent flight test from Zhukovsky. The aircraft is the only Su-27M prototype so far to have been seen with the TVC. The TVC mechanism appears to be fitted in addition to the standard convergent/divergent nozzle. Flight testing began in the second quarter of 1996. The image clearly shows the extent to which the aircraft's tail-sting extends beyond the nozzles. This may limit nozzle movement in the yaw plane.
Sukhoi has previously claimed that the Su-27M would enter service with the Russian air force fitted with TVC, although this seems unlikely.
Source: Flight International