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National Advisory Committee for Aeronautics, Technical Notes - Effect of Retractable Spoiler Location on Rolling and Yawing Moment Coefficients

In this report are presented the results of wind—
tunnel tests of retractable spoilers on the upper surface
of a Clark Y wing, which have been made as part of an in—
vestigation of lateral control devices being conducted by
the National Advisory Committee for Aeronautics. Spoilers
with chords up to 15.0 percent of the wing chord were teet-
ed in several locations on a plain rectangular wing and in
two locations on the same wing equipped with a 20. 0 per-
oont chord split flap down 60

Charts are given for four representative angles of at-
tack from which values of rolling~ and yawing—moment coef-
ficients may be obtained for spoilers up to 15. 0 percent
chord located on the upper surface of a Clark Y wing.

The tests showed that at low angles of attack prac—
tically the same rolling moments can be obtained with a
given spoiler at any location back of 30.0 percent of the
wing chord. while at high angles of attack there is a def~
inite advantage in locating the Spoiler at least as far
forward as 30. 0 percent of the chord. The yawing moments
accompanying a given rolling moment increase p0s_itively as
the spoiler location is moved forward from the trailing
edge of the wing. It is concluded that the 30. 0 percent
chord location is probably the optimum provided that in~
stantaneeus response of the airplane to a control movement
can be obtained.

The National Advisory Committee for Aeronautics has
undertaken an investigation of the effectiveness of vari-
ous lateral control devices, particularly at high angles
of attack (reference 1). As a part of the investigation
a hingedwplate spoiler located 20 percent of the wing
chord (c) from the leading edge was tested in the wind '
tunnel (reference 2) and in flight (reference 3). The
flight test showed that this type of spoiler had the ob~
Jectionable characteristic of delayed response of the air—
plane to a movement of the spoiler. In an effort to over-
come this lag. a retractable spoiler consisting of a

curved plate hinged at the center of curvature was tested
which presented a sharp-edged projection to the air flow
well forward on the wing (15.0 percent c location) and
which. it was hoped, would give instantaneous response. _

Flight tests with this device, however, showed longer lag '
than with the hingedeplate spoiler. Since ordinary aile—
rons have-nonnoticeable lag. it was believed that moving
the locationjof-the spoiler rearward along the wing chord
might materially reduce the lag. With this idea_in mind,
the present investigation was made to determine the effect
on the rolling and yawing moments of moving the spoiler
rearward.