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National Advisory Committee for Aeronautics, Technical Notes - Tests of an NACA 23012 Airfoil with a Slotted Deflector Flap

Section aerodynamic characteristics of a large—chord
N.A.G.A. 23012 airfoil with a slotted deflector flap were
obtained in the N.A.G.A. 7~ by lO~foot wind tunnel. The
characteristics of an N.A.0.A. slotted flap and of a sim—
ple split flap are included for comparison.

The slotted deflector flap was found to have a some-
what lower maximum lift coefficient and somewhat higher
drag at high lift coefficients than the N.A.G.A. slotted
flap. At moderate lift coefficients, however, the drag of
the slotted deflector flap was about the same as that_of
the N.A.C.A. slotted flap. The high drag of the open slot
with the deflector flap neutral indicates that the slot
should be closed for this condition.

Many present—day airplanes use some form of lift—
increasing device to aid in taking off and in landing.
Among the more desirable characteristics of such devices
are high maximum lift with relatively low drag, low mini~
mum drag and, possibly, high lift with high drag. One of
the most promising of such devices appears to be some form
of slotted flap.

The results of an investigation of a slotted deflec—
tor flap are given in this paper. The distinguishing
characteristics of the slotted deflector flap are a very
large slot and a deflector plate mounted on the leading
edge of the flap. Results from similar tests of a split
flap and an N.A.C.A. slotted flap (one of the most promis—
ing slotted flaps developed to date by the N.A.C.A. (ref—
2 N.A.C.A. Technical Note No. 599
erence 1)) are included for comparison.
Egiélq— The airfoil was built of laminated pine tcthe
N.A,G.A. 23012 section and has a chord of 3 feet and a span
of 7 feet. Data for the design of the slotted deflector
flap were furnished by the United Aircraft Corporation.

The deflector is a metal plate mounted on the flap leading
edge, as shown in figure 1.

Eind'tunnel.~ The model was mounted on the standard
two—dimensional~flow set—up in the N.A.C.A. 7— by 10—foot
closed~throat wind tunnel, which is described in reference 1.

lest§.— The tests were made at a dynamic pressure of
16.37 pounds per square foot, corresponding to an air
speed of about 80 miles per hour at standard sea~level con—
ditions and an average test Reynolds Number of 2.190.000-
The turbulence factor of the tunnel is 1.6; the effective
Reynolds Number, therefore, is approximately 3.500.000-

The flap was tested in what was specified as the most
effective location by the United Aircraft Corporation at
deflections of 0°, 10°, 20°, 30°, 40°, 50°, and 60°. Enough
angles of attack were taken to determine envelope polars
over the complete lift range from zero to maximum lift.