NACA

NACA is the Acronyme of “National Advisory Committee for Aeronautics” which means “national advisory committee for aeronautics”, committee which existed in the United States of 1915 to 1958 before being replaced by NASA.

History

This committee existed March 3rd 1915 at October 1st 1958. It was then replaced by NASA.

During this period, this committee published a great number of reports/ratios and technical notes on subjects concerning aviation. It also led a good portion of research of the E. - U., in aeronautics.

In the beginning, the goal of this committee was to organize the aeronautical research of the USA to raise it on the level of European aviation. Some of its first reports/ratios are besides translations of German work such as the n°16 report/ratio of 1918 or the technical note 66 of 1920.

These documents are consultable on http://naca.central.cranfield.ac.uk

In addition to the technical sides, the NACA also gave opinions aiming at organizing the aircraft industry and the civil exploitation of aviation. Its recommendations, made in 1925, inspired the “Air Trades Act” of 1926.

Nevertheless the essence of its activities related to the research and the development with an aim of working out practical solutions. In 1917, in order to fill the delay of the E. - U. compared to the Europe, the NACA establishes “Langley Memorial Aeronautical Laboratory” in Virginia.

Outstanding results (very partial list)

Among the results of carried out work one will note:

Reduction in the Trailed by the suitable shape of the engine cowlings (Years 1920)
Drag decrease grace the provision of the engines on the leading edge (and not out of nacelle) (Years 1920)
Study and measurement of the performances of the families of profiles of wing known under designations NACA to 4 or 5 digits (Years 1930)
Study and measurement of more elaborate profiles until the supercritical profiles (series NACA 6,7 and 8)
Research on the prevention of icing on the wings, the Propeller S and in the Carburizing S
Experimentation in flight of the extreme configurations of flight (left gimlets with various positions of the center of gravity)
Study of the sweptback wings (after the Second world war and the Germans)
Just after the Second world war: translation of the German documents describing the reaction engine
Study of the passage of the Wall of the sound: participation in the X1 program.
Establishment of the Law of the surfaces, (Whitcomb, 1952), which stipulates that the trail is minimal when the curve of the surfaces (evolution of the cross sections of the plane of before to the back) is continuous. It is thus recommended to decrease the section of the fuselage at the level of the wings: fuselage in " cut guêpe".

Profiles NACA with 4 digits

The 4 figures describe the geometry of the profile. They use the length of the cord of the wing as unit; the cord is the straight line which joint the leading edge at the edge of escape.

the first figure gives the Cambrure expressed as a percentage profile length of the cord.
the second figure gives the position of the maximum camber in tenth of the cord.
the last two figures expressed as a percentage give the maximum thickness of the profile of the cord.

Thus, this system with the advantage simultaneously of naming a profile and of describing its form. Unfortunately this system only makes it possible to cover a negligible proportion of the possible profiles.

Bonds and reference

National The Advisory Committee for Aeronautics (NACA)
NACA DIGITAL Library - the U.K. Mirror
NACA Airfoil Series

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