# FORCES ON THE WING

The vertical velocity of the wing section distant у from the center line is

z = h(y)zT (5.10,2)

and the corresponding change in wing angle of attack is

Да(у) = h(y)zTfUf) (5.10,3)

This angle of attack distribution can be used with any applicable steady-flow wing theory to calculate the incremental local section lift. (It will of course be proportional to t/JUfy) Let it be denoted in coefficient form by C’j(y)zT/u0, and the corresponding increment in wing total lift coefficient by C’LJzTlu0. CJ(y) and C’u are thus the values corresponding to unit value of the nondimensional quantity zT/u0.

FORCE ON THE TAIL

The tail experiences a downward velocity h(0)zT, and also, because of the altered wing lift distribution, a downwash change (Эе/Эіт)іт – Hence the net change in tail an­gle of attack is

Эе

Да, = h(0)zT/uo – іт

OZf

Г Й£ 1 Zr

= m – —— —

diXjiW0) J Uq    This produces an increment in the tail lift coefficient of amount

THE DERIVATIVE Z,

ZT    This derivative describes the contribution of wing bending velocity to the Z force act­ing on the airplane. A suitable nondimensional form is dCz/d(zT/u0). Since Cz = —CL, we have that     and hence