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• November 30, 2016 Create Date
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National Advisory Committee for Aeronautics, Technical Notes - Wind Tunnel Investigation of an NACA 23030 Airfoil with Various Arrangements of Slotted Flaps

An investigation was made i'n the N. A. C. A. T— by 10-
foot wind tunnel of a large— chord N. A. G. A. 23030 airfoil
with a 40and a 25.66—percent-chord slotted flap to de-
termine the section aerodynamic characteristics of the'
airfoil as affected by flap chord, slot shape, flap posi-
tion, and flap deflection. The flap positions for maxi-
mum lift, the positions for minimum drag at moderate and
high lift coefficients. and the complete section'aerody-
namic characteristics of selected optimum arrangements
are given. Envelope polars of various flap arrangements
are included. The relative merits of slotted flaps of
different chords on the N.A.C.A. 23030 airfoil are dis-
cussed, and a comparison is made of each flap size with a_
corresponding flap size on the N.A.C.A. 23021 and 230i?
airfoils.

The lowest profile-drags at moderate lift coeffi—-
cients were obtained with an easy'entrance to the slot.
The 25.66-percent~chord slotted flap gave.somewhat lower
drag than the 40-percent—chord flap for lift coefficients
less than 1.8, but the 40—percent—chord flap gave consid—
erably lower drag for lift coefficients from 1.8 to 2. 5
and a larger value of the maximum lift coefficient. The
drag coefficients at moderate and high lift coefficients
were greater with both sizes of flap on the N.A.C.A. 23030
airfoil than on either the N.A.C.A. 23021 or the N.A.C.A.
23012 airfoil. The maximum lift coefficient for the de-
flections tested with either flap was practically inde—
pendent of airfoil thickness.‘

The National Advisory Committee for Aeronautics has
been conducting an extensive investigation of wing-flap
combinations for the purpose of improving safety and per—
formance. For take-off and initial climb. a wing-flap
combination capable of producing moderately high lift
with low drag is dosiroblel On the other hand, landing
requirements probably make a device with high lift and
variable drag desirable. Furthermore, such a device
should give a small increase in drag when the flap is re—
tracted and should give low operating forces and a mini—
mum chenge in pitching moment with change in flap deflec—
tion.