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National Advisory Committee for Aeronautics, Technical Notes - The Effect of Partial Span Split Flaps on the Aerodynamic Characteristics of a Clark Y Wing

Aerodynamic force tests were made in the N.A.C.A. 7
by 10 foot wind tunnel on a model Clash Y wing with a 20
percent chord split flap deflected 60 downward. The
tests were made to determine the effect of partial— —span
split flaps, located at various positions along the wing
span, on the aerodynamic characteristics of the wing—and—
flap combination. The different lengths and locations of
the flaps were obtained by cutting off portions of a full~
span flap, first from the tips and then from the center.
The results are given in the form of curves 6f lift,
drag, and center of pressure. They show that with partial-|
span split flaps both the lift and drag are less than with
full-span flaps; that the lift for a given length of flap
is somewhat greater when the partial span is located at
the center of the wing than when it is located at the tip
portion; and that the drag for a given length of flap is
the same regardless of the location of the flap with re—
spect to the wing span.
Among the devices for increasing the maximum lift and
also the drag of an airplane to improve the landing char—
acteristics, is the split trailing—edge flap. With this
arrangement the rear portion of the wing is split_ into up-
per and lower sections and the lower section is deflected
downward as a flap. This type of flap is designed for use
over the maximum possible length of the wing span, no per-
tion of the flap serving for lateral control.
Some tests have previously been made on airfoils with
split flaps (references 1, 8,-3 , -and 4) in which the ef-
fects of changes in flap chord and deflection have been
investigated, The present investigation was made to de-
termine the effects of changes in flap length and location
along the wing span. The flaps were tested on a Clark Y
wing in the 7'by 10 foot wind tunnel, and lift. drag, and
pitching moment were measured for each size and location
of flap. Only split flaps with a chord 20 percent of the
wing chord were used since previous investigations indi-
cated that flaps of this chord size would give results of
most general value.