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National Advisory Committee for Aeronautics, Technical Notes - Pressure Distribution and Damping in Steady Pitch at Supersonic Mach Numbers of Flat Swept Back Wings Having All Edges Subsonic

A method is presented for calculating the pressure distribution and.
damping in steady pitch at supersonic Mach numbers of thin, flat, swept—
back wings having all edges straight and subsonic. Although it is adapt—
able to wings with negative rake at the tips, the method is applied only
to wings with streamwise tips.

The method consists of two steps: first, the calculation of a basic
pressure distribution, which is identical to that existing on an infinite
triangular plan form having leading edges that coincide with those of the
swept—back wing; and second, the correction of this basic distribution to
account for the effects of the subsonic trailing edges and tips. In cal—
culating the various corrections, use is made of the principle of the
superposition of conical flows. The derivative for the damping in pitch
is calculated in a similar manner.

In applying the method of analysis to a typical configuration, it
was found that several of the corrections .were small, and, from a practi—
cal standpoint, could be dropped. By dropping these terms the method is
shortened to the extent‘ that it closely parallels previously published
methods for calculating the lift, pitching m'oment, and damping in "roll of
swept—back wings with subsonic edges.

A substantial reduction of the pressure in the vicinity of a subsonic
tip was disclosed in the analysis. This effect was also found earlier for
the cases of steady lift and steady roll.

The method is based upon the usual assumptions and limitations of
the linearized potential theory for supersonic flow.

Methods have been develoPed previously for the calculation of the
pressure distribution and the damping in steady pitch at supersonic Mach
numbers for thin, flat wings of various plan forms, including triangular
wings (reference 1), rectangular wings ‘(reference 2), wings with super—‘
sonic leading edges but somewhat arbitrary plan form (reference 3); and
swept—back wings having all supersonic edges or a combination of subsonic
leading edges and supersonic trailing edges and tips (references 1|- and 5).:-
An approximate analysis of the damping in pitch of a limited class of -
swept—back wings having all edges subsonic and straight is reported in
reference 6. In the present report, a method, which can be applied more
generally than that of reference 6, is presented for the analysis of swept—
back wings with straight subsonic edges.