Investigation of the Lift Distribution Over the Separate Wings of a Biplane Page: 2 of 41
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1 II1 1 I111ill III1 II
3 1176 01440 6640
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
TECHNICAL MEMORANDUM NO. 889
INVESTIGATION OF THE LIFT DISTRIBUTION
OVER THE SEPARATE WINGS OF A BIPLANE*
By D. Kchemann
An investigation is made of the mutual interference
of the wings of a biplane under the general assumption
that each wing may be replaced by a vortex system of the
type given by the Prandtl wing theory. The additional ve-
locities induced at each wing by the presence of the other
are determined by the Biot-Savart law and converted into
an equivalent change in angle of attack, the effect being
that of an additional twist given to the wings in changing
their lift distributions. The lift distributions computed
in this manner for several airplane types are compared
with the results of measurement.
Notation
In general the subscript o will denote the value
for the upper wing, whereas the subscript u will denote
the corresponding value for the lower wing;
x, y, z, rectangular coordinates (right-hand system); the
y axis laid in the direction of the bound
or lifting vortex of the lower wing positive
to starboard, origin taken at the center of
the wing, and the x axis forward
a, stagger of the biplane system = separation of
lifting vortices in the x direction
h, wing gap = separation of lifting vorticesin the
z direction
t, wing chord
b, wing span
*"Berechnung der Auftriebsverteilung tiber die einzelnen
Fligel eines Doppeldeckers." Luftfahrtforschung, Oct. 10,
1938, pp. 543-55.
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Küchemann, D. Investigation of the Lift Distribution Over the Separate Wings of a Biplane, report, March 1939; (https://digital.library.unt.edu/ark:/67531/metadc63276/m1/2/: accessed March 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.