https://www.rbth.com/defence/2017/08/02/russias-fifth-generation-fighter-jet-gets-a-new-heart-and-a-new-name_815520
Russia’s fifth-generation fighter jet gets a new ‘heart’ and a new name
August 2, 2017 BORIS EGOROV, NIKOLAI LITOVKIN
Formally known as the PAK FA, the Su-57 is an improved fighter jet with a new advanced engine that trumps its American counterparts.