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National Advisory Committee for Aeronautics, Research Memorandum - Wind Tunnel Investigation of Horizontal Tails - I - Unswept and 35° Sweptback Plan Forms of Aspect Ratio 3

The results are presented'of a wind—tunnel investigation of the
low—speed characteristics of horizontal tails of aspect ratio 3
with unswapt and. swept—back plan forms. Two models were tested.
which had identical areas, aspect ratio, taper ratio, and airfoil
section, differing only in the angle of sweepback and elevatgr area
ratios. Data are presented for Reynolds numbers of 3.0 X 10 and.
1+.O >.< 10° with the elevator sealed and for a Reynolds number of
3.0 x 106 with the seal removed and with standard. roughness applied
to the leading edge.

The major effect of sweepback, as measured from the tests of
the two models, was to increase the rate of change of hinge-moment
coefficient with angle of attack, to reduce the rate of change with
elevator deflection, and. to reduce the elevator effectiveness.

An investigation of. the theoretical prediction of control—
surface hinge moments by lifting—sm'face theory has been undertaken
by the NASA. The lifting—surface theory is a further refinement
to the lifting—line theory to obtain more accurate predictions. This
report presents the experimental results obtained on the first two.
of a series of models to determine the validity of the theoretical
computations and the extent of aspect ratios over which they are
valid. The comparisons with the theoretical calculations are not
presented herein but will await the results of tests of models of
aspect ratios 4.5 and 6.

Another equally important purpose of the investigation was to
evaluate the effects of sweepback by a comparisOn of the results
of tests of two models with the same area, aspect ratio, taper
ratio, and airfoil section, differing mainly in the angle of sweep—
back.

The present investigation included the measurement of the lift,
hinge-moment, and pitching—moment coefficients, and the pressure
coefficients across the elevator nose seal of the semispan hori—
zontal tails of unswept and swept-back plan forms and. an aspect
ratio of 3. The effects of Reynolds number, standard roughness on
the leading edge, and removal of the elevator seal were also
determined.