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National Advisory Committee for Aeronautics, Technical Notes - Investigation of Deflectors as Gust Alleviators on a 0.09-Scale Model of the Bell X-5 Airplane with Various Wing Sweep Angles from 20° to 60° at Mach Numbers from 0.40 to 0.90

An investigation was made in the Langley high—speed 7- by 10-foot
tunnel to determine the effectiveness of a given deflector arrangement
as a gust alleviator on a 0.09-scale model of the Bell X-5 airplane with
various wing sweep angles from 200 to 60° at Mach numbers from 0.h0
to 0.80 over a maximum angle-of—attack range from approximately —5°
to 21.

Deflectors were effective as gust alleviators (reduction of the
lift-curve slope measured through 0° angle of attack) at all wing sweep
angles; however, the magnitude of lift—curve-slope reduction varied with
Mach number and wing sweep angle. For this particular deflector instal-
lation (projection of 15 percent average chord and span of 0.25 wing
semispan located along the 55—percent—chord line of the unswept wing),
the configuration with 50° swept wings had the maximum reduction in
lift-curve slope and the minimum variation with Each number (from approx-
imately 29 percent at a Mach number of 0.h0 to approximately 21 percent
at a Mach number of 0.90). The deflectors caused an increase in drag at
all Mach numbers and wing sweep angles of this investigation and, con-
sequently, would be effective as aerodynamic brakes.

At the lower angles of attack (linear portion of the lift curve),
the longitudinal stability of the wing configurations for angles of
sweep from 200 to 50° was increased by the addition of the deflectors.

At higher angles of attack as the Mach number was increased, pitch—up
was evident for both the basic model and the model with deflectors. The
severity of the pitch-up and the angle of attack when the pitch-up occurs
are closely associated with the nonlinearity of the lift curve. Over the
angle-of—attack range of the present investigation the deflectors caused
no marked effect on the longitudinal stability of the 60° sweptnwing
model. It appears that, generally, if the basic model.had no pitch-up
problem, the deflectors did not cause pitch—up; hOWever, if the basic
model had pitch-up, the deflectors tended to increase pitch-up.