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National Advisory Committee for Aeronautics, Technical Notes - Development of the NACA Slot Lip Aileron

An investigation of the undesirable delayed action,
or lag. of the spoiler-type lateral control device led to
the development of the N. A. C. A. slot— lip aileron. The
tests were made in the 7- Aby 10—foot wind tunnel with a
4— by 8—foot wing hinged at the tunnel jet boundary and
restrained in roll by elastic cords. Time histories were
taken of the motion of the control device under test and
of the resulting wing motion.
First, the lag, as affected by the fore—and—aft loca—
tion of retractable ailerons or spoilers was determined.
The lag was found to increase regularly as the spoiler was
moved from the rear of the wing toward th-e _front. Then a
combination of spoiler and fixed slot was develoPed that,
with the spoiler retracting into the forward part of the
slot, reduced the time lag to a negligible value, In ad—
dition, an arrangement was developed using a hinged aile-
ron—type flap as the upper portion, or lip, of a slot
through the wing. This arrangement appears to be usable“
as a form of lateral control device that shows promise of
giving improved control and stability at the high angles
of attack through the stall, with negligible lag. low con-
trol forces, and relatively simple construction.
Owing to the fact that safety in flight can be  in—
creased by improving the lateral control and stability at
high angles of attack the National Advisory Committee for
Aeronautics has undertaken an investigation with that aim
(reference 1). Wind—tunnel tests have shown that spoiler-
type devices located in the forward portion of the wing
should give improved rolling'and yawing moments at high
angles of attack (reference 2). Flight tests have re~
vealed, however,_thot the spoiler_control is accompanied
by a delayed response, or lag, (reference 8) unless looat»
ed well back on the wing (reference 4). The present-work
was undertaken to investigate the nature of this lag un~
der controlled conditions in'a wind tunnel and to explore
the possibilities of obtaining a.device having spoiler-
type control without lag.