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National Advisory Committee for Aeronautics, Technical Notes - Experimental Investigation of the Effect of Vertical Tail Size and Length and of Fuselage Shape and Length on the Static Lateral Stability Characteristics of a Model with 45° Sweptback Wing and Tail Surfaces

An investigation was made to determine the effects of vertical-tail
size and length and of fuselage shape and length on the lateral static
stability characteristics of a model with wing and vertical tails having
the quarter—chord lines swept back hso. The results indicate that the
directional instability of the various isolated fuselages was about two-
thirds as large as that predicted by classical theory. A reduction in
area of vertical tails (geometric aspect ratio kept constant) attached
to a given fuselage resulted in an increase in the effective aspect ratio
of the vertical tail for the range of tail sizes considered. Simple
analytical considerations indicate, however, that for tail sizes below
the range investigated, the opposite effect would be expected.

For the fuselage-tail combinations investigated, the tail effec-
tiveness usually decreased with increasing angle of attack, with the
greatest rate of decrease occurring at angles of attack greater than
about 16°.

The wing—fuselage interference for the midwing arrangements inves—
tigated was only slightly affected by the shape of the fuselage and
tended to increase Slightly'the directional stability of the'combination.
The interference effects of the wing tended to decrease the vertical—
tail effectiveness, particularly at high angles of attack. The large
effects observed were attributed to a partially stalled condition of the
Wing.

Recent advances in the understanding of the principles of high-speed
flight have led to significant changes in the design of the principal
components of airplanes. Two of the more important changes have been the
incorporation of large amounts of sweep of the wing and tail surfaces and
the elevation of the horizontal tail to a higher position. Much informa—
tion is available on the influence of the wing, fuselage, and tail geome—
try on the static stability characteristics of the more conventional
airplane designs (for example, references 1 and 2); however, little
information is available on the influence of the various airplane come
ponents on the characteristics of airplanes having wings and tail sur-
faces with large amounts of sweep. In order to provide such information,
a series of investigations is being conducted in the Langley stability
tunnel with a model having various interchangeable parts. The effects
of changes in the size and location of the horizontal tail on the low-
speed static lateral stability characteristics have been reported in
reference 3. The effects on the static—lateral—stability derivatives
of variations of vertical-tail size and length and of fuselage shape and
length are presented herein. The data also have been used to determine
interference effects between the wing and fuselage and the interference
effects of the wing-fuselage combination on the vertical-tail effectiveness.