In any aircraft it is important to use your airspeed indicator while side-slipping. The pitot tube, for the best part, and being in the direction of normal airflow, will in fact influence the airpeed indicator so that it tells you the component of airflow over the wings in the normal sense. During the side-slip you would, thus, expect to see the airspeed drop if the deck angle remains the same. Nose the aircraft down and recover the airpeed to your approach speed. What the airspeed indicator tells you is what the wings are getting in the normal sense, the tail should not be affected or 'balnked' if you have the correct airspeed reading.