that row of screw holes is probably not as big a problem for stealth as it might seem because it is aligned with the leading edge of the wing, so it is planform aligned will reflect radar back along the same prescribed direction as the main airframe.
Soviet style military aircraft had always been cheap in willing to accept a very rough finish where the finish didn’t matter too much, compared to gold plated western products. so for example su-27 and Mig-29 didn’t even use countersunk rivets that fits flush with aircraft skin in areas where bumps didn’t disturb the airflow in flight.
But the Su-57 has many more fundamental design issues from stealth perspective, such as absence of a serpentine air intake duct so the radar bright fan blades of the front of the engine is directly visible from the front, and many exterior seams, hatches and canopy rails lack serrated edges to provide planform alignmemt.
so su-57 might be considered a reduced observably design rather than stealthy design by international standards.
Soviet style military aircraft had always been cheap in willing to accept a very rough finish where the finish didn’t matter too much, compared to gold plated western products. so for example su-27 and Mig-29 didn’t even use countersunk rivets that fits flush with aircraft skin in areas where bumps didn’t disturb the airflow in flight.
But the Su-57 has many more fundamental design issues from stealth perspective, such as absence of a serpentine air intake duct so the radar bright fan blades of the front of the engine is directly visible from the front, and many exterior seams, hatches and canopy rails lack serrated edges to provide planform alignmemt.
so su-57 might be considered a reduced observably design rather than stealthy design by international standards.
