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National Advisory Committee for Aeronautics, Technical Notes - Span Load Distribution for Tapered Wings with Partial-Span Flaps

Tables are given for determining the load distribution of
tapered wings with partial-span flaps placed either at the
center or at the wing tips. Seventy~two wing-flap com-
binations, including two aspect ratios, four taper ratios,
and nine flap lengths, are included. The distributions for
the flapped wing are divided into two parts, one a zero
lift distribution due primarily to the flaps and the other an
additional lift distribution due to an angle of attack of the
wing as a whole.

Comparisons between theoretical and experimental
results for wings indicate that the theory may be used to
predict the load distribution with sufiicient accuracy for
structural purposes.

Simple computing forms are included for determining,
by the Lotz method, the theoretical loadings for a combina-
tion of any wing with any flap. A discussion of the
method is given showing: (1) the eject on the load dis-
tribution of increasing the number of harmonics for a
wing with partial-spanfiaps; and (2) the efiect of increas-
ing the number of points used across the semispan for a
wing of unfair plan form.

A knowledge of the span load distribution over a
wing is important not only from structural considera-
tions but also because certain conclusions regarding the
behavior of the wing near the stall may be drawn from
it. Indirectly, the span load distribution also influences
such items relating to performance as the magnitude
of the induced drag, the pitching moment of the entire
wing about an aerodynamic center, and the angle of
zero lift. Because of the importance of span load
distribution, numerous methods for computing it have
been proposed but, since they are generally lengthy
and complicated, they have been little used in practice.

In reference 1 the span loading was given for linearly
tapered wings with rounded tips. The results given
therein cover a large range of aspect ratios and taper
ratios, but they are for the case of a wing in which there
is either no twist or only linear twist. Since most
airplanes include some sort of high-lift or drag-increas-
ing device covering only part of the span, the wing with
an abrupt twist is of particular interest.