I need a formula to calculate the speed of air moving over an RC airplane. Because the plane will not be flying above 2000 ft and this plane flies at less than 15 miles per hour max, the formula can be very basic I think. Example of sensors: I have two very sensitive barometer (temperature compensated), one is for the altitude and the other is for speed of the aircraft in air( similar to a pitot tube). The plane has a GPS for the ground speed of the plane. The need for the air speed of the aircraft is to be used to guide the control computer as to the amount of input into the controls to accomplish tasks (turn, climb rate etc). Because the airplane flies so slowly power must be applied to get enough air flow across the rudder to cause a turn. Many times the plane is standing still in a slight breeze or even appears to fly backward.