Page 201 - Aerodynamics for Engineering Students
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184 Aerodynamics for Engineering Students
Note that a positive flap deflection, i.e. a downwards deflection, decreases the
moment coefficient, tending to pitch the main aerofoil nose down and vice versa.
4.5.1 The hinge moment coefficient
A flapped-aerofoil characteristic that is of great importance in stability and control
calculations, is the aerodynamic moment about the binge line, shown as Hin Fig. 4.16.
Taking moments of elementary pressures p, acting on the flap about the hinge,
trailing edge
pd dx
H = -Jhge
where p = pUk and x’ = x - (1 - F)c. Putting
c
C
C
x/=-(i -cose)--(i-cos~) =-(cos~-cose)
2 2 2
and k from Eqn (4.51):
+,( (1 -;) COS4Il - (1
(4.54)
where
’t
Fig. 4.16
