# The lift and moment of the tail equations

We have

The lift of the tail,

$$L_t = C_L.q.S_t$$

The moment of the tail around c.g.

$$M_(cg,t) = C_M.q.S.c$$

look at the S in the two equations.

Why the lift of the tail is proportional to the surface of the tail while the moment of the tail about c.g. is proportional to the surface of the wing ?

If I consider the moment of the tail as the tail lift multiplied by the arm, then the moment will be independent of S, the surface of the wing.

• What is $S_t$? how does it differ from $S$? – Manu H Jun 22 '20 at 17:51
• $S_t$ is the tail surface.$S$ is the wing surface – hadi floka Jun 25 '20 at 8:01