NO. 5 STABILITY OF AEROPLANES HUNSAKER AND OTHERS 



19 



plane and moving with it in space. In the normal attitude, the axis 

 of X is tangent to the trajectory of the center of gravity with its 

 positive direction toward the rear. The axis of c is normal to x and 



Fig. 7. — Coordinate axes, x, y, 



y in the vertical plane, and the axis of y horizontal and directed to the 

 left. The axes are shown in figure 7. As the aeroplane rolls, yaws, 

 and pitches these axes move with it. so that ^ is no longer in the 

 vertical plane of x, nor y horizontal. 



