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National Advisory Committee for Aeronautics, Technical Notes - Effect of Spoiler Type Lateral Control Devices on the Twisting Moments of a Wing of NACA 230 Series Airfoil Sections

The effects of several spoiler arrangements on the spanwise
variation of section twisting moments of a wing of NACA 230-series
airfoil sections were investigated. The spoilers'tested included
both plain and perforated spoilers. The tests were conducted at
a Reynolds number of 7,350,000 and a Mach number of 0.2h5; the
tests included force and moment measurements and chordwise pressure-
distribution measurements at six spanwise stations.

The results of the tests indicated that the influence of a
proJected spoiler on the section pitching-moment coefficients
extended approximately 25 percent of the semispan inboard of the
spoiler. The maximum twisting-moment coefficients due to the
spoilers at a low angle of attack of the wing were reached at this
spanwise location-

A region of negative pressure coefficients existed directly
behind the projected spoiler and diminished the positive pitching-
moment tendencies. This low pressure region became intensified
near the tip and, in some cases, caused negative local twisting
moments. Consequently, the smalleSt maximum twisting moment
due to a spoiler for a given rolling moment may be obtained by
locating the outboard end of the-spoiler as close to the tip as
possible to take advantage of the increased balancing moment-

The perforations caused the pressure coefficients directly
behind the spoiler to increase, and a greater maximum twisting
moment resulted. The rolling moments of the perforated and the
plain spoilers, however, were the same within the experimental
accuracy of the tests.

Either an extension of the spoiler span inboard from the tip
or an increase in spoiler proJection increased both the twisting-
moment coefficients due to the spoiler and the rolling-moment
coefficients. For a given change in rolling-moment coefficient,
however, an extension of the spoiler span resulted in greater
increases in twisting moments due to the spoiler than did an
increase in spoiler projection.