Objectives

We want glider flight models that:

1. Accurately reflect the glider polar i.e. it's sink rate at every speed, flap setting, and ballast load.
2. Behave accurately near the stall - glider pilots get close to this, e.g. when thermalling, much more often than power pilots.
3. Have airbrakes and flaps that work progressively and accurately. It's virtually impossible to land a high-performance sailplane without effective flaps and airbrakes.

Current status

X-Plane looks like it has quite detailed control over how the flight model behaves although this involves complex manipulation of a hidden 3d model. But with effort it seems possible to get good flying characteristics.

An example of x-plane glider flight model improvement is lordauriel's work on the ASK21 Realistic Flight Model . There is an interesting forum thread with comment as the flight model was improved here

XPlane glider airfoil design

XPlane aircraft parameters affecting the flight model

... more coming soon...