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┃    ┃     n l;7 hl } ┃       n a~z h/7 __ ┃    ┃
┣━━╋━━━━━━━━╋━━━━━━━━━━┫    ┃
┃    ┃UOr u~i_        ┃         UjO UI{ -- ┃    ┃
┃    ┃   ~,h          ┃                    ┃    ┃
┃T)  ┃                ┃      uJ (-         ┃    ┃
┣━━┻━━━━━━━━┻━━━━━━━━━━┻━━┫
┃                 ' r^ ^'NG-EDGE  DROOP            ┃
┃                    /-BASIC AIRFOiL               ┃
┃                                                  ┃
┃  ------_--                                       ┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━┛
10
TOTAL
RESULTANT
FOttCe
COEFFICIOIT
U1ng leading-edge modtfication to out-
board wlng panel of airplane A.
b)
o    IO   ZO   30   O
       ANGLE OF ATTACK, deg
o    10   20   30   40
      AN6LE OF ATTACK, deg
Fig. 7.25    An example ofwing leading-edge modification,23.24 continued.
667
668            PERFORMANCE, STABILITY, DYNAMICS, AND CONTROL
Strake
                   b) Strakes
Fig. 7.26    Examples ofmodification offuselage geometry.
in significant improvement in spin resistance oflight general aviation airplanes.
The spins exhibited by modified airplanes are much steeper and slower compared
to the baseline airplanes.19
       The aerodynamic flow mechanisms giving rise to these beneficial effects are dis-
cussed elsewhere.26,27 Essentially,these modifications alter the sectional side force
coefficient characteristics from prospiri type A to antispin-type B (see Fig. 7.8).
As a result, the fuselage contribution becomes more damping in nature.
Example 7.2
    A Light single-engine, general aviation airplane has the following data: gross
 weight =  10,915 N, wing span =  9.9822 m, wing area -  13.53 m2, mean aerody-
namic chord = 1.34 m,lx  = 2304 kg/m2,ly  = 2602 kg/m2, andlz = 4336 kg/m2.
       This aircraft has a steady spin mode at an angle of attack of 40 deg. The aircraft
takes about 3 min per tum and spins with right wing 5 deg below the horizontal
plane. Assuming that the resultant force coefficient at 40 deg angle of attack is
equal to 1.2, determine 1) velocit3r of descent, 2) spin radius as a fraction of
wing semispan, 3) angular velocity components in the body axes system, and 4)
aerodynamic moments acting on the airplane during the steady-state spin. Assume
sea level conditions.
                                                        siriOy = -cos a sin X
With Qy = 5 deg and a - 40 deg, we get X  = -6.5326 deg.
INERTIA COUPLfNG AND SPIN
~
      The angular velocity components are given by
                                                                 p = s? cos cy cos X
　
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