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National Advisory Committee for Aeronautics, Technical Notes - Full Scale Force and Pressure Distribution Tests on a Tapered USA 45 Airfoil

This report presents the results of force and pres-
sure—distribution tests on a 2:1 tapered U.S.A. 45 air—
foil as determined in the full—scale wind tunnel. The
airfoil has a constant—chord center section and rounded
tips and is tapered in thickness from 18 percent at the
root to 9 percent at the tip. Force tests were made
throughout a Reynolds Number range of approximately
2,000,000 to 8,000,000 providing data on the scale effect V
in addition to the conventional characteristics. Pressure-
distribution data were obtained from tests at a Reynolds
Number of approximately 4,000,000. The aerodynamic char-
acteristics giVen by the usual dimensionless coefficients
are presented graphically.

For a portion of an extensive wing—fuselage interfer—
ence program being carried out in the N.A.G.A. full~scale>
wind tunnel, it was necessary to obtain pressure-distri- A.
bution and force tests upon a tapered U.S.A. 45 airfoil.
This particular airfoil section is a feature of the air-
plane used in the main investigation; otherwise a more
commonly used section would have been chosen. The paucity
of full~scale information on the aerodynamic characteris—
tics of tapered airfoils warrants the presentation of ‘
these data as a report separate from the results of the
wing—fuselage interference investigation.

The airfoil constructed primarily to coonform
with the requirements of a wing-fuselage interfer—
ence investigation is of standard weed and fabric aircraft
construction. Fries—type ailerons.

The airfoil (fig. 1) has a Span of 45.75 feet, an as~
pact ratio of 6.20. and a mean chord of 7.38 feet; the
area is 337.5 square feet. -A constant-chord center sec-
tien extends 10.7 percent of_the semispan from the center
line of the airfoil;' The plan form, from the center sec—
tion outboard, is determined by a basic trapezoid tapered
2:1; the rounded tips are formed within the trapezoid.