When the flight model is active, this quaternion is the plane's master position; writing to it will change the plane's orientation. Writing to the pitch heading and roll of the plane will have no effect; see MovingThePlane for more info.
sim/flightmodel/position/Q is the yaw rotational rate of the plane in degrees per second. See MovingThePlane for more info.
Datarefs are case sensitive (but this web site is not).