Dramatic framerate drop

[Roger_Meatball]

My game runs between 40-60 FPS regularly, but routinely it drops down to 3-4 FPS for no reason I can understand. Sometimes it's in menus or mission briefings or in flight. I can't recreate the bug reliably, but it happens every 10 minutes or so. The framerate drop will last for several seconds or sometimes until the screen type changes (if I'm in menus, it won't fix itself until I get back into the game).