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• December 13, 2016 Create Date
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National Advisory Committee for Aeronautics, Technical Notes - Effect of Horizontal Tail on Low Speed Static Lateral Stability Characteristics of a Model Having 45° Sweptback Wing and Tail Surfaces

An investigation.has been conducted in.the Langley stability
tunnel to determine the effects of changes in horizontal—tail size and
location on the static lateral stability characteristics of a complete
model with wing and tail surfaces having the quarter—chord line swept
back #50. '

Available procedures, based on analyses of unswept—tail configu—
rations, for predicting the effect of the horizontal tail on directional
stability, were found to be unreliable when applied to swept—tail
configurations.

When the horizontal tail was located at the base of the vertical
tail, diSplacement.of the horizontal tail rearward increased the
favorable contribution of the horizontal tail to directional stability
at low angles of attack; at high angles of attack, the contribution of
the horizontal tail was unfavorable regardless of the horizontal locar
tion. When the horizontal tail was located near the top of the vertical
tail, the contribution of the horizontal tail was highly favorable at
low angles of attack; at high angles of attack, the largest favorable
effect was obtained with the horizontal tail in a forward location.

The trends obtained with the wing on were similar to those obtained
with the wing off, but a large decrease occurred in the favorable effect
obtained at large angles of attack with the horizontal tail in the upper
positions; a probable explanation was the detrimental effect of the wing
wake arising from flow separation over the wing.

Recent advances in the understanding of the principles of high—
speed flight have led to significant changes in the design of the major
component parts of airplanes. In many instances, consideration is
given to configurations which are beyondthe range covered by available
design information regarding stability characteristics. {the effects of
changes in wing design on stability characteristics have been exten—
sively investigated. In_order to provide information on the influence
of other parts of the complete airplane, an investigation of a. model
having various interchangeable component parts is being conducted in
the Langley stability tunnel. As part of this investigation, the effect
of changes in the size and location of a swept horizontal tail on the
static—lateral—stability derivatives was determined.