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National Advisory Committee for Aeronautics, Report - Wind Tunnel Investigation of an NACA 23012 Airfoil with a Slotted Flap and Three Types of Auxiliary Flap

An inrestigation was made in the N. A. C. A. ‘7- by
10-foot wind tunnel to determine the aerodynamic section
chardcteristics of an N. A. 0. A. 23012 airfoil with a
single main slotted flap equipped successirely with aux-
iliary flaps of the plain, split, and slotted types. A test
installation was used in which an airfoil of 7-fOOd span
was mounted certically between the upper and the lower
sides of the closed test section so that two-dimensional
flow was approximated.

0n the basis of maximum lift coeflicient, low drag at
moderate and high'lift coeficients, and high drag at high
lift coefiicients, the optimum combination of the arrange-
ments was found to be the double slotted flap. All the
auxiliary flaps tested, however, increased the magnitudes
of the pitching moments over those of the main slotted
flap alone.

Many different types of high-lift device have been
investigated by the N. A. C. A. in an extensive program
of research for increasing safety in flight. Some of
these devices are located at the leading edge of the
wing and others at the trailing edge. One of the most
promising of the devices is a recently developed arrange-
ment of slotted trailing-edge flap. This slotted flap
(reference 1) is capable of giving high maximum lift
coefficients, low drag at moderate and high lift coeffi-
cients, and high drag at high lift coeflicients. This
flap therefore appears well suited for improving take-
off and landing characteristics.

Results of a few preliminary tests of a slotted flap
with a small split flap mounted on it (reported also in
reference 1) indicate that such an arrangement has
considerable promise as a high-lift device. As a fur-
ther development in enlarging the possibilities of the
slotted flap, the investigation has been extended to
include multiple flaps. The present report gives the
results of an investigation of an airfoil with a medium-
size main slotted flap combined with each of three
different types of smaller auxiliary flap: split, plain,
and slotted.