曝光臺 注意防騙 網(wǎng)曝天貓店富美金盛家居專營店坑蒙拐騙欺詐消費(fèi)者

 altitude of18,000 m, we find that the Reynolds numberis equal to 11.20x 10J. From
STATIC STABILITY AND CONTROL
291
Fig. 3.74, we get K Rt: 1.97. Substituting in the above expression for fuselage
contribution, we get (Cnp)B(W) - -0.00242]deg.
   Now let us approximately evaluate vertical tail contribution. We have Av.eff =
2.4236, Au - 0.2951, and ALE., = 45 deg. From Fig. 3.14, we get t3 (CNcr)theory  =
3.85/rad, where [3 : -/_      f = 1.732. -fhis gives (CNcr)theory = 2.2228/rad_
Note that p here is not sideslip angle.
   Now we need to apply the sonic leading correction to the above value of CNa
using the data given in Fig. 3.15a. We have Ay = 2.5 so that AYi = Ay/cos A =
3.5360. With this, we obtain from Fig. 3.15a, CNa/(CNcr)theory = 0.825 so that
CNa  -  1.8338/rad or 0.0320/deg, and ay  = 0.032/deg. All the other values in the
expression for vertical tail contribution remain unchanged. Substituting, we obtain
                                 (C,zp.v)rix = 0.00249ldeg
Then,
                                 Cnp = (Cnp)B(W) + (Cnp.V)fix
                                                             - -0.00242 + 0.00249
                                  = 0.00007/deg
We observe that the given aircraft has marginal static directional stability at M =
2.0. However, it should be noted that this result is based on a very crude estimation
of vertical tail contribution.
Example 3.9
   An aircraft is ready for takeoff when it is detected that a crosswind of 8 m/s
is blowing across the runway. Determine the rudder angle required to maintain
a steady normal heading along the runway at unstick point using the following
data.
    Wing loading ( W/S) = 2500 N/m2, span = 25 m, wing area = 70 m2, unstick
velocity -. 1.2  Vsrall, maximum lift coefficient - 1.8, lift-curve slope of t.he verti-
cal tail= 0.08/deg, (Cnp)fix  =  0.012/deg, vertical tail volume ratio = 0.25, and
r7u - 0.9. Assume that 1 deg of rudder deflection changes the vertical tail incidence
by 0.4 deg.
   So/ution.   Assuming sea level conditions (p = 1.225 kg/m3), the stalling ve-
Iocity is given by
Vstall =
- 47.6191 m/s

t?.z:.
  ; 9tj
     .:, -:""-.
      b-: :
   a- :
292            PERFORMANCE, STABtLITY, DYNAMICS, AND CONTROL
We have
Assuming k - l, we have
Vunstick - 1.2 Vsrall
        - 57.1429 m/s
 p = tan-l 57.18429
- 7.9696 deg
Cn8r - -kay V2r7yt2
Cn8r  - -0.08 * 0.25 * 0.9 * 0.4
    - -0.0072ldeg
   -.p(C,,p)tjx
                        8r -.-
          CnBr
                                                           = 13.2827 deg
The rudder should be deflected to the left by 13.2827 deg.
                                     Example 3.10
    A twin jet engine has the following data: thrust per engine = 10,000 N, span-
 wise distance between the two engines = 10 m, w~~ area =50 m2, wing span =
 10 m, rudder effectiveness (Cn8r) = -O.OOlldeg, and maximum permissible rud-
 der deflection -.:+::20 deg. Determine the rudder deflection to maintain zero sideslip
　
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