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National Advisory Committee for Aeronautics, Technical Notes - Analysis of Wind Tunnel Data on Directional Stability and Control

Available windutunnel data on static directional sta~
bility and control have been collected and studied. Meth—
ods based on these studies are given for evaluating the
aerodynamic characteristics of vertical tail surfaces and
their contribution to static directional stability and
control. Special attention has been paid to the end-plate
effect of the horizontal tail on the vertical tail and to
the sidewash induced by the fuselage and the trailing vor~
tex system from the wing. Methods based.on limited data
for fuselases and hulls, wings, and fuselage-wing combina~
tions are also given for.estimatins the contribution of
the wins and the fuselage to directional stability.

This paper does not attempt to establish criterions
for directional stability and control; rather. the empha-
sis is placed on providing some basis for design to spec-
ified criterions. An example applying the design methods
has been included.

As a part of a general investigation directed toward
developing a rational system of.tail design, a study has
been made of available wind-tunnel data on directional
stability and control.. The main emphasis has been placed
on a study of the.aerodynamic characteristics of the ver—
tical tail surfaces and their contribution to the static
stability and control characteristice of airplanes. Data
on the characteristics of yawed fuselaees, hulls, wings.
wins~fuselage combinations, and wing—hull combinations
have also been collected. The purpose of this study has
been not to establish the stability and control criterions
for-satisfactory flight handling characteristics but rath~
er to provide methods for design.to specified criterions.

Rudder—effectiveness data.wer0‘available for 4 air—
planes and 28 models, including two 35-foot-span models
of multiengine airplanes. The contribution of the verti—
cal tail to stability, that is} yawing moments for both
tail—attached and tail—removed conditions, was available
for eight of these models. 'Yawing—noment data for fuse—
lagcs and hulls were available for 17 models. For 4 of
the 17 models, yaw tests had also been made of the wing
alone and of the wing—fuselage combination.