In that way
it is not necessary to depart so far from the normal angle
of incidence at which the lift-drift ratio is highest.
Wash-in is the term applied to the increased angle.
Wash-out is the term applied to the decreased angle.
Both lateral and directional stability may be improved
by washing out the angle of incidence on both sides of the
surface, thus:
The decreased angle decreases the drift and therefore the
effect of gusts upon the wing-tips which is just where they
have the most effect upon the aeroplane, owing to the distance
from the turning axis.
The wash-out also renders the ailerons (lateral controlling
services) more effective, as, in order to operate them, it is
not then necessary to give them such a large angle of incidence
as would otherwise be required.
The less the angle of incidence of the ailerons, the better
their lift-drift ratio, i.e., their efficiency. You will note
that, while the aileron attached to the surface with washed-out
angle is operated to the same extent as the aileron illustrated
above it, its angle of incidence is considerably less. Its efficiency
is therefore greater.
The advantages of the wash-in must, of course be paid for
in some loss of lift, as the lift decreases with the decreased angle.
In order to secure all the above described advantages,
a combination is sometimes effected, thus:
BANKING.--An aeroplane turned off its course to right
or left does not at once proceed along its new course.
Pages:
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108