Sollte der hier sein. Ich habe es auf 25000 gestellt.
MAX_TEXTURE_REQUEST_DISTANCE = 1000
This setting can be used to change the distance that is used to request textures of aircrafts and library objects that are not visible. This prevents the objects from rendering with a black texture when looking at it after it has been out of view for a certain amount of time. The larger the distance the more graphics memory that is required.

