General Relationships Between the Various Systems of Reference Axes Employed in Flight Mechanics

The different possibilities of orientation of the systems of axes currently employed in flight mechanics are compiled and described. Of the three possible couplings between the wind and aircraft axes, the most suitable coupling is that in which the y axis is made the principal axis of rotation for one of the two coupling angles (angles of attack). In connection with this coupling, an experimental system of axes is introduced, whose axes x(sub e) and z(sub e) are situated in the plane of symmetry of the airplane and rotate about the airplane lateral axis y = y(sub e). This system of axes enables the utilization of the coefficients obtained in the wind tunnel in the flight-mechanic equations by a simple transformation, with the aid of the angle of attack, measured in the plane of symmetry of the airplane.