I think that Shuttle Fleet 4.8R2 was developed for Orbiter 2010, so if you are using Orbiter 2016, that might be some kind of incompatibility...
Re-entry effects in Obiter2010 are triggered when density times velocity cubed exceeds a preset threshold. This can be wrong on both sides, displaying the effects at relatively low Mach numbers at low altitude or not displaying effects at orbital velocity in the high atmosphere.
Rho V cubed is not only wrong, it is over-thought. A much more appropriate trigger criteria could only have to consider the Mach number being above a certain threshold (I believe Mach 12 or so) and the vehicle being within a detectable atmosphere.
I would say that when one tries to decide whether to render re-entry flames, they should consider the heating of the air (via shock heating), and not on the vehicle.
Thanks for the reply. But do you have any idea of what the d3d9 client does differently to make the flames appear early?Well, if you are fast enough, plasma will form around the spacecraft. Independent of the air density, that just increases how dense the plasma is. Generally, all visualizations are wrong though. If you look at shuttle launch videos, you can see how faint greenish plasma already dances around the ET before separation. It turns pink during reentry with changing atmospheric composition.