The q Derivatives (CZq, CmJ

These derivatives represent the aerodynamic effects that accompany rotation of the airplane about a spanwise axis through the CG while ax remains zero. An example of this kind of motion was treated in Sec. 3.1 (i. e., the steady pull-up). Figure 5.2b shows the general case in which the flight path is arbitrary. This should be contrasted with the situation illustrated in Fig. 5.2a, where q = 0 while ax is changing.

Both the wing and the tail are affected by the rotation, although, when the air­plane has a tail, the wing contribution to CZq and Cmq is often negligible in compari­son with that of the tail. In such cases it is common practice to increase the tail effect by an arbitrary amount, of the order of 10%, to allow for the wing and body.