Can airflow reverse over the flight surfaces of a uav in high wind conditions Can airflow reverse over the wing of a uav in high tail winds and low forward airspeed i.e 25knt fwd airspeed in a 35 knt tailwind? What would be the overall effect on the elevator and rudder? I suspect the rudder would be remain the same but operate at a reduced efficiency however, wouldn't the function of the elevator reverse and/or become ineffective, especially at high angles of attack? As a point of note, this uav does not have ailerons, I believe the roll effect is achieved as a combination of pitch and yaw.
It is possible, but only if there were a very sudden and dramatic change that the aircraft was unable to overcome.  However, it would be only temporary.  

If the airflow direction was actually reversed the control surfaces would likely be blown to a full deflection position one way or the other depending on which side of neutral they were.  

Otherwise, the aircraft would still move forward at 25kts relative to the moving airmass, with the additive effect of the wind giving it 60kts of ground speed.