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NASA, Technical Memorandum - Computer Program to Obtain Ordinates for NACA Airfoils

Although modern high-speed aircraft generally make
use of advanced NASA supercritical airfoil sections,
there is still a demand for information on the NACA
series of airfoil sections, which were developed over
50 years ago. Computer programs were developed in the
early 1970’s to produce the ordinates for airfoils of any
thickness, thickness distribution, or camber in the NACA
airfoil series. These programs are published in refer-
ences 1 and 2. These programs, however, were written in
the Langley Research Center version of FORTRAN IV
and are not easily portable to other computers. The pur—
pose of this paper is to describe an updated version of
these programs. The goal was to combine both programs
into a single program that could be executed on a wide
variety of personal computers and workstations as well
as mainframes. The analytical design equations for both
symmetrical and cambered airfoils in the NACA 4-digit—
series, 4—digit—modified—series, 5-digit—series, 5—digit—
modified-series, l6—series, 6—series, and 6A-series airfoil
families have been implemented. The camber—line desig-
nations available are the 2—digit, 3-digit, 3-digit—reflex,
6-series, and 6A—series. The program achieves portability
by limiting machine—specific code. An effort was made
to make all inputs to the program as simple as possible to
use and to lead the user through the process by means of
a menu.

The design equations for the analytic NACA airfoils
and camber lines have been presented in references 3
to 7. They are repeated herein to provide a better under-
standing of the computer program and indicate the use of
different design variables. A summary of some of the
design equations and ordinates for many airfoils from
these families is also presented in references 8 to 10.

The traditional NACA airfoil designations are short—
hand codes representing the essential elements (such as
thickness-chord ratio, camber, design lift coefficient)
controlling the shape of a profile generated within a
given airfoil type. Thus, for example the NACA 4—digit-
series airfoil is specified by a 4—digit code of the form
pmxx, where p and m represent positions reserved for
specification of the camber and xx allows for specifica-
tion of the thickness—chord ratio as a percentage, that is,
“me2” designates a 12-percent-thick (t/c = 0.12) 4-digit
airfoil.