for fuselage Surface objects. If the fuselage wasn't aligned perpendicular
to the Y axis, the matrix wouldn't be orthonormal. Since all of, perhaps,
three aircraft have ever been built this way, it's doubtful I would have
found this as a bug report. :)
Math::unit3(fwd, x);
y[0] = 0; y[1] = 1; y[2] = 0;
Math::cross3(x, y, z);
+ Math::unit3(z, z);
+ Math::cross3(z, x, y);
s->setOrientation(o);
_model.addSurface(s);