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National Advisory Committee for Aeronautics, Technical Notes - Calculated Spanwise Lift Distributions and Aerodynamic Influence Coefficients for Unswept Wings in Subsonic Flow

Spanwise lift distributions have been calculated for nineteen
unswept wings with various aspect ratios and taper ratios and with a
variety of angle-of-attack or twist distributions, including flap and
aileron deflections, by means of the weissinger method with eight control
points on the semispan. Also calculated were aerodynamic influence coef—
ficients which pertain to a certain definite set of stations along the
span, and several methods are presented for calculating aerodynamic
influence coefficients for stations other than those stipulated.

The information presented herein can be used in the analysis of
untwisted wings or wings with known twist distributions, as Well as in
aeroelastic calculations involving initially unknown twist distributions.

In the design and development of an airplane, a knowledge of the
spanwise lift distribution on the wing is important in predicting the
structural loads and the stability characteristics. For high-speed air-
planes having flexible wings, the calculation of the spanwise lift dis-
tribution is an aeroelastic rather than a purely aerodynamic problem.

In aeroelastic calculations means are required for calculating the span-
wise lift distribution for angle-of-attack (or twist) distributions which
are initially unknown. Aerodynamic influence coefficients constitute the
most convenient of these means.

One of the most satisfactory techniques developed in recent years
for calculating the spanwise lift distribution on a wing in subsonic flow
has been the weissinger L—method (ref. 1), which can be applied to a
large variety of plan forms and yields solutions of sufficient accuracy
for all practical purposes without requiring an unduly long time for the
calculations. This method may be considered as a simplified lifting—
surface theory because the calculation of the lift on_the wing is treated
as a boundary-value problem, the boundary condition being that the down-
wash angle induced by the bound and trailing vortices is equal to the
geometric angle of attack at the three-quarter-chord line.