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National Advisory Committee for Aeronautics, Technical Notes - Lateral Stability and Control Characteristics of a Free Flying Model Having an Unswept Wing with an Aspect Ratio of 2

Tests have been made in the Langley free—flight tunnel to determine
the lateral stability, control, and general flying characteristics of a
free—flying model having an unswept wing with an aspect ratio of 2. The
tests were made at a lift coefficient of 1.0 and covered a range of
geometric dihedral angles from —20° to 20° and a range of vertical—tail
areas from O to 15 percent of the wing area. The results of these tests
were compared with the previously reported results of a similar series
of tests on a conventional model having a wing with an aspect ratio
of 6.

The general flight behavior of the low-aspect—ratio model was not
so good as that of the conventional model for corresponding values of
static directional stability and effective dihedral. The primary cause
of the difference in the flight behavior of the models was the adverse
yawing moments due to aileron deflection which, as would be expected
from theory, were considerably larger for the loweaspect—ratio model
than for the conventional model.

In the transonic and supersonic speed range, low~aspect—ratio
unswept wings appear to offer some of the advantages of swept wings,
particularly as regards drag. In addition, IOWhaspect—ratio unswept
wings appear to have better static stability characteristics than
swept wings in the high—lift—coefficient range and may offer some
structural advantage over swept wings. Hence, a great deal of interest
has been shown in the use of low—aspect—ratio unswept wings for high—
speed airplanes.

An investigation has therefore been conducted in the Langley free—
flight tunnel to provide some basic information on the effects of aspect
ratio on the lateral stability and control characteristics of airplanes
with unswept wings. Flight tests were made with a model having an
unswept wing with an aspect ratio of 2. All of the flight tests were
made at a lift coefficient of 1.0 and covered a range of dihedral angles
from —20° to 20° and vertical tail areas from 0 to 15 percent of the wing
area. Sufficient combinations of dihedral angle and vertical tail area
were covered to determine the effects of these parameters on lateral
stability and control characteristics and general flying characteristics.
The results of the flight tests are presented in the form of qualitative
ratings of the oscillatory stability and general flight behavior of the
model for each test condition.