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80                PERFORMANCE, STABILITY, DYNAMfCS, AND CONTROL
The maximum range occurs when the glide angle is minimum
            1
ynun - En
               1
     - 28 86
- 0.0346 rad
= 1.985 deg
The velocity and lift coefficient for the fiattest glide are given by
                     V : VR
.~  If4[F~
\1  .225~8 OV 0.015
- 23.328 m/s
CL = C:
    - 0.866
Example 2.2
     A glider weighing 5000 N and having an elliptical wing with an area of 10 m2 is
required to maintajn a glide angle of3 deg at a forward speed of 50 m/s. Assuming
CDO - 0.015, find the aspect ratio of the glider.
So/uOon.    Because the glider has an elliptical wing, e - 1. Then,
            CD
                    y- CL
     3
= 5~30
-. 0.0524 rad
AIRCRAFT PERFORMANCE
C~ = p2S~
                     2 *5000
     = ~25~0~502
      - 0.3260
 CD - CLy
            - 0.326 * 0.0524
      - 0.01708
kC~. = CD - CDO
    k = O 01708 - 0.015
                 0 3262
          - 0.0196 .
             1
A--
  k7te
                  1
 =00~96 7r*l
        - 16.20
81
2-4 LeveIFlight
      The forces acting on an airplane in level :flight are shown in Fig.  2.7. In level
flight, the airplane is at a constant altitude so that h = y = 0. With this, Eqs. (2.7)
and (2.8) take the following form:
/- W _O
T-D-O
(2.61)
(2,62)
                                                 
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┃        -- o-        -. ┃          ~ \ Rit   ┃
┃                        ┃--,-                ┃
┃                        ┃     ~}  '          ┃
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┃                        ┃            a    l. ┃
　
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