The T-50 (PAK-FA) is intended to be the successor to the MiG-29 and Su-27 in the Russian Air Force and serve as the basis for the Fifth Generation Fighter Aircraft (FGFA) being co-developed by Sukhoi and Hindustan Aeronautics Limited (HAL) for the Indian Air Force. The T-50 prototype first flew on 29 January 2010 and production aircraft is slated for delivery to the Russian Air Force starting in 2016.
The PAK-FA appears to be optimized for the air-superiority role like the F-22 more so than the multirole, strike-optimized F-35. Like the Raptor, the PAK-FA is being designed to fly high and fast to impart the maximum amount of launch energy to its arsenal of long-range air-to-air missiles—which would greatly increase the range of those missiles.
Variants of the T-50 and the timeline
Defending Russia has the timeline and plans for Su-50 fighter development.
South Korean may get a getting version with local avionics and it would be coded Su-50EK. The Su-50EK is planned for 2018.
Su-50E twin seat version might be co-developed with India with completion around 2020.
In 2020, Sukhoi plans the Su-55-FGFAM which would be a further modernized twin seat version.
The Russian Air Force is expected to procure more than 150 PAK FA aircraft, the first of which is slated to be delivered in 2016. India planned on acquiring modified PAK FA as a part of its Fifth Generation Fighter Aircraft (FGFA) program. India is currently planning to take 144 single-seat aircraft.
The T-50 has two tandem main internal weapon bays each approximately 4.6 m (15.1 ft) long and 1.0 m (3.3 ft) wide and two small triangular-section weapon bays that protrudes under the fuselage near the wing root. Vympel is developing ejection mechanisms for the main weapons bays that can accommodate 300 kg to 700 kg loads. The internal carriage of weapons preserves the aircraft's stealth, reduces drag and improves performance compared to external stores. The T-50's high cruising speed is expected to substantially increase weapon effectiveness compared to its predecessors. The aircraft has an internally mounted 9A1-4071K (GSh-301) 30 mm cannon near the right LEVCON root.
The Su-30, CY-30 history
SOURCES - Wikipedia, Su-27flanker, Defending Russia, National Interest