388
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PERFORMANCE, STABILITY, DYNAMICS, AND CONTROL
    Flight Path
_/_h _
Fig.4.18    Forces acting on an airplane during a pull-out maneuver.
For the disturbed flight,
                 Fx -. Fxo + AFx -. -(Do + AD) - W sin(0o + AO) + T
                                                                                                                                                                      \ U)?-
   Fz -- Fzo + AFz = -(Lo + AL) + W cos(0o + AO) - ( v~   [(Uo +RAf/
so that
                                                 AFx -. -AD - W cos 0o AO
                        AFz = -AL - W sinOoAO - (V;~) [2URAU ]
 Proceedingin a similar way as we did for the small disturbance equations ofmotion
for a steady flight in a vertical plane, we obtain
                                    Cxu - -2CD - CDu
                                    xcr : -CDa
                                                           Cx0 - -CL COS 0o
                                        Cxct - -CDd - 0
                                         Cxq = -CDq - 0
                                 Czu = -2CL - CLu - 2tTl,iqo
                                    zct : -Cln
                                      zd - -CLdt
                                     Czq = -CLq
                                              Cz8 - -CL siri0o
The expressions for other lateral-directional stability derivatives essentially remain
the same as those derived earlier for steady ffight. However, we have to note that
EQUATIONS OF MOTION AND ESTIMATION OF STABILITY DERIVATIVES 389
all the stability derivatives have to be evaluated for curved flow conditions to sim-
　
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