Worst stealth design among all 5th gen jets, it have only frontal aspect stealth, with least plan-form alignment properties, it have 2 piece canopy with metal bar between it which increases RCS, IRST also increase RCS, LAVCON deflection also somehow increases RCS and Biggest RCS points are air intakes, which place almost same place s on Su-27 series of jets which may also increases RCS, i think Su-57 is the modified version of Su-27 series of jets with only frontal aspect stealth only, its is LO design but not VLO design like F-22/J-20 but think Russia don't need VLO design because they have different doctrine/strategies and philosophies for their fighter jet development as compare to west and China, and they have backup of latest gen SAMs (S-400/S-500)