I found turning off Photogrammetry helps with the stutters
I own KIAD, KDEN and KPDX FlightBeam airports. KDEN and KPDX runs great in my sistem (RX 580, Ryzen 5 2600, 16 GB ram) but KIAD is heavy as a fat man eating in McDonald’s… OMG eats all my FPS 
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But I think KIAD decreased performance after SU9… I remember it was running ok before 