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National Advisory Committee for Aeronautics, Technical Notes - Wind Tunnel Pressure Distribution Tests on a Series of Biplane Wing Models - Part I - Effects of Changes in Stagger and Gap

This report furnishes information on the changes in the
forces on each wing of a biplane cellule when either the stagger
or the gap is varied. The data were obtained from pressure dies
tribution tests made in the Atmospheric Wind Tunnel of the
Langley Memorial Aeronautical Laboratory. Since each test Was
carried up to 90° angle of attack, the results may be used in
the study of stalled flight and of spinning as well as inlthe
structural design of biplane wings.

This report presents the results of wind tunnel pressure
distribution tests which were made in order to determine the
magnitude and dispositiou.of the normal or “beam" air loads on
two wing models arranged in different biplane combinations.

The effects of changes in stagger and gap were investigated
separately. A subsequent report, Part II, will cover the re—
sults of similar tests in which the decalage, dihedral, sweepe
back and overhang were varied.

This investigation forms the second part of a program of
force, pressure distributionland autorotation tests on a syste—
matic series of wing models through a large angle of attack
range. All the tests are being made in the Five—Foot Atmos—
pheric Wind Tunnel (Reference 1) of the Langley Memorial Aero—
nautical Laboratory, -The force'test part of the program has
been completed and two reports (References 2 and 3) have been
prepared on the results, The autorotation1tssts are to be made
in the near future.

This test program.comes under a general study of the aero—
dynamic factors affecting airplane safety. For this reason, all
the tests are carried up to 90° angle of attack,

The informationxin this report and in Part II may_be ap—
plied to the structural designxof biplane wing systems. The re~
sults also have a bearing on safety in stalled flight and on
spinning.