Mike wrote:
XCSoar has an artificial horizon? I did not know that.

Yes:

http://git.xcsoar.org/cgit/master/xc...nderer.cpp#n35

The code has been there for many years, but is disabled, the comment
says why. (Not my opinion/decision, I would not put artificial limits
on technology used by XCSoar)

This code will be reinstated when Johnny (and the rest of the
OpenVario project) finishes his new vario design, which includes a
real AHRS. The OpenVario project started long before Butterfly
announced their vario, but since it's a spare time project of a few
soaring geeks, it takes a bit longer.

Max