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National Advisory Committee for Aeronautics, Report - The Aerodynamic Effects of Wing Cut Outs

In connection with the interference program being con—
ducted in the N.A.C.A. variable-density wind tunnel, an
analysis was made of available material with the object
of presenting a qualitative discussion of wing character-
istics as afiected by cut-outs and of determining means for
their quantitative calculation.
The analysis indicated that extending a cut—out in the
chord direction has much greater efiect than attending it
in the span direction. Unfairness in profile over the
leading edge of the cut-out sections adversely afiects the
lift and induced drag as well as the profile drag.
Lifting-line airfoil theory can be successfully used to
calculate the characteristics of a wing as afiected by a cut-
out when the section characteristics of the profiles along
the span are known. It is useful, in such a problem, to
employ the method of successive approximation for ab-
taining the span load distribution.
The information derived from the analysis was applied
for illustration to the prediction of the characteristics of a
wing with a center-section cut-out. The values thus
obtained were found to agree fairly well with the test
results of a model of the cut—out wing measured inthe
variable-density wind tunnel.
It is sometimes desirable to cut out portions of a
wing, usually at the center. Such a change in plan
form may, however, produce large changes in the char-
acteristics of the wing. Therefore, information that
would guide a designer in his choice of a cutwut and
enable him to calculate the aerodynamic character-
istics of cut-out wings should prove useful.
The information now available concerning wing
cut-outs or applicable to the analysis of their effects is
plentiful (references 1 to 7) but too disconnected and
unorganized to be of the greatest possible usefulness.
In connection with the interference program being
conducted in the N.A.C.A. variable-density wind tun-
nel, an analysis was therefore made of existing material
to determine the qualitative effects of the different
features of wing cut-outs, and to obtain means of cal—
culating wing characteristics as affected by them.