Why do so many Russian fighter jets still use IRST?

Posted by CracklyTurtle64@reddit | aviation | View on Reddit | 249 comments

I saw that video of that SU 57 landing in China today. I guess I never really noticed before, but I saw that it still has the IRST module in front of the cockpit. Why do Russian aircraft, even new 5th gen fighters like the Su57 Felon and the SU75 checkmate still use IRST. I know that in the US fourth GEN fighters still do have the ability to use IRST but only as an add-on module and not integrated into the air frame. To me it just seems like a very archaic design that may at one time had usefulness, but today seems much inferior to modern AESA phased array, radar sets.