T-50-2 has no radar and features a long pitot tube at the nose tip. Along with T-50-1, it is used for performance and handling tests.
During more than five years of trials, the T-50 prototypes have made about 600 flights, a sixth of those necessary for testing the fighter.
The PAK FA 101KS-N navigation and targeting pod has been under test since 2011.
The fourth prototype, T-50-4, carrying dummy versions of air-to-ground Kh-31s and air-to-air R-77s - the Sukhoi T-50 has yet to fire missiles. The basic ordnance load is carried in two large weapon bays in tandem inside the fuselage while close-air combat missiles fit in two small underwing fairings close to the engines' inlets.
T-50-5 is under repair after sustaining serious damage in a fire on June 10, 2014.
The purpose of one of the 101KS Atoll electro-optical sensors, the 101KS-O, is unclear. It is presented by the Russians as an infrared jammer for self-defence, but is probably an infrared search-and-track sight.
The N036-01-1 forward-looking X-band electronic-scanning antenna comprises 1,552 transceiver modules and is tilted about 15 degrees up.
Su-57 prototype T50-3 loaded with R-73 and R-77 air-to-air missiles on underwing pylons. The long-range R-77M version features a multifunction doppler monopulse active radar seeker, strakes fitted at the mid-fuselage position, conventional fins at the tail, and a dual pulse rocket motor.
T-50-3 carrying dummy R-77 and R-73 missiles in the Aviadarts demonstration. This aircraft, as well as T-50-4 and T-50-5, is equipped with N036 AESA radar in basic configuration with single forward antenna only.
A model of the Prospective Multi-role Fighter, or Type 79L, to be developed jointly by Russia and India.