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National Advisory Committee for Aeronautics, Technical Notes - Investigation of a Slat in Several Different Positions on an NACA 64A010 Airfoil for a Wide Range of Subsonic Mach Numbers

An investigation of the two—dimensional aerodynamic characteristics
of an NASA 6hAOlO airfoil with a slat has been conducted in the Mach num-
ber range from 0.25 to 0.85, with a corresponding Reynolds number range
from 3.h million to 8.1 million.. Two families of slat positions were
investigated, one with the slat leading edge extended forward along the
airfoil chord line, and the other with the slat extended forward and dis-
placed below the chord line.

The results indicate that for section lift coefficients up to 0.6,
the airfoil with the slat retracted generally was aerodynamically superior
to any of the other airfoil-slat arrangements investigated. The drags
with the slat nose on the extended chord line were only slightly higher
than the drag with slat retracted, whereas displacing the slat nose below
the chord line markedly decreased the drag-divergence Mach number. Above
0.7 section lift coefficient and at the higher test Mach numbers, the best
results were obtained with the slat nose on the extended chord line of the
airfoil.

At the lower test Mach numbers, the highest maximum lifts were meas-
ured with the slat nose displaced below the wing chord line. At super-
critical speeds, however, adverse effects such as occur with cambered
airfoils resulted with the slat nose below the airfoil chord line. These
adverse effects were large increases in drag and in angle of attack for
zero lift and large negative trim changes.

High-lift devices have been used extensively for improving the land—
ing and take—off performance of all types of airplanes. One of these
devices, the leading-edge slat, has been used to increase maximum lift and
lift-drag ratio and, also, to improve lateral stability and control at
high angles of attack by delaying the stall over the outer portions of the
wing and ailerons. In recent years the use of slats and wing leading-edge
modifications has been directed at improving the characteristics of swept
wings at high speeds as well as at low speeds. Further research also
appears desirable on the development of slats for use on thin unswept
wings suitable for supersonic flight.