Stick Force for a Horizontal Stabilizer-Elevator Combination

The relationship for stick force and stick force gradient will now be developed for the horizontal tail configuration of Figure 8.7b. Such a configuration is trimmed either by changing the incidence of the horizontal stabilizer (so in a sense it is not fixed) or by deflecting a small flap, known as a trim tab, on the trailing edge of the elevator. The particular method of trim is not pertinent to the present development.

Assuming a symmetrical airfoil section, the elevator hinge moment coefficient will be written in the same form as Equation 8.32

8, refers to the trim tab, as shown in Figure 8.9. Following the same procedure as for the all-movable tail, it can be shown that

F’= (t)a + [fi2 ~ b)ihs + b}8t~ в]™у2 (838)

Cl„ (Cm6Clb — СцаСц) ЬгСіСи

If iks or 5, is adjusted to trim P to zero at a trim speed of FTR, Equation 8.28 becomes

зЬИІМ’-ШІ <8-з9>

The rate of change of stick force with speed will be

dP 2GSece(WIS)A dVra Ftr