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                                          L - W                                 (2.34)
                                        x - V                                (2.35)
                                     h = Vy                             (2.36)
Lift and drag forces are given by
                                                             L -  21p V 2SCL                                             (2,37)
                               D = ;p V2SCD
                                         = ~2pl/2'      o +kCZ)
           _ r2S(CDO.          (2.38)
The velocity is given by
'v _
(2.39)
AIRCRAFT PERFORMANCE
The glide angle can be obtained from Eqs. (2.33) and (2.34) as
                        D
                                  )/ = -W
                        D
       =-L
               CD
                                                   = - CL
so that
        1
= -E
75
(2.40)
  Dnun
Ynun - N-
      W
                1
      = - E~                                    (2.41)
Thus, the fiattest glide (y = Ynun) occurs when the glider fiies at that angle of attack
when the drag per unit weight is minimum or E = Em. Because the weight of a
glider is constant, we can say that the fiattest glide occurs when the drag is at
minimum. We know that when E = Em, CL = C7. =.            7k. The fiight velocity
for the fiattest glide is given by
V --
(2.42)
In other words, the velocity for the fiattest glide is equal to the reference velocity
or u ~ 1.
   For a given height, the distance covered with respect to the ground can be
obtained as follows:
dx = V .                           (2.43)
　
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