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National Advisory Committee for Aeronautics, Technical Notes - Low Speed Wind Tunnel Investigation of Various Plain Spoiler Configurations for Lateral Control on a 42° Sweptback Wing

A low-speed wind-tunnel investigation of an emloratory nature has
been performed to determine a satisfactory location for a spoiler lateral-
control device for a sweptback wing. ‘The semispan wing used for the
tests had 42° sweepback referred to the wing leading edge and an aspect
ratio of 1+.Ol. Spoilers having a projection of 10 percent of the local
wing chord were tested at various spanwise and chordwise locations and
skew angles. The variation of rolling effectiveness with spoiler pro-
Jection was determined for one of the most effective locations.

The results showed that a spoiler consisting of a group of segments
located near the trailing edge of the wing, slightly inboard from the
wing tip, and skewed with reference to the wing so as to be perpendicular
to the free-stream air flow had the most nearly constant and highest
values of rolling-moment coefficient throughout the usable lift range
and would exhibit fairly high values of maximum rolling moment. These
spoilers were found to have some of the objectionable characteristics
previously found for plain spoilers on unswept wings, namely a reduction
of maximum control effectiveness at high angles of attack and a region
of ineffectiveness or reversed effectiveness at small spoiler projections.

One of the many problems arising from the use of sweptback wings
on high-speed aircraft has been that of securing adequate lateral control.
In order to obtain solutions to this poblem, the National Advisory
Committee for Aeronautics is currently investigating the applicability
of various types of lateral-control devices to sweptback wings. One type
of lateral—control device that appears to offer some advantages is a
spoiler. Some possible advantages of the spoiler—type control device
(see references 1 to 5) are the favorable yawing moments associated
with spoilers and the fact that, because of the location of the spoilers,
the trailing edge of the wing is available for full—span, high—lift flaps.
In addition, the wing twisting moments produced by the deflected spoiler
will probably be small in comparison with the twisting moments produced
by an aileron of the same rolling power and the spoiler will probably
have smaller operating forces. .The lag in rolling response of the
deflected spoiler may, however, be objectionable.