Relax! There's nothing wrong with the old FSX or the current PREPAR3D.
I've noted a number of forum complaints over this issue and I had very good reason to believe that FSX and PREPAR3D had a fault.
I nearly always sim fly (and real fly) from Redcliffe in Australia and the simulator windsock definitely indicates 180 degrees wrong. If you're going to teach general flying with Prepar then this detail is very important. For this reason I spent 3 hours resolving this issue and I'm convinced that the fault lies with the Redcliffe airfield scenery model. I tried airfields in the northern hemisphere and the southern hemisphere and Brisbane International (nearby) noted gps groundspeeds versus TAS's and couldn't fault the sim programs.
The perceived explanation of local thermal winds as being the cause is frivolous.
I hope this helps someone.
genairco
