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National Advisory Committee for Aeronautics, Technical Notes - The Pressure Distribution Over a Douglas Wing Tip on a Biplane in Flight

This note presents the results obtained in pressure dis—
tribution tests on the right upper wing panel and tip of a
Douglas M—S airplane in flight. These tests are a part of a more
extensive investigation of the effect of changes in tip shape
on the load distribution, the tip reported herein being the
first of a series of six shapes being tested.
The results are given in tables and curves in such form
that the load distribution for any conditions may be determined
easily.

The distribution of load over the tips of airplane wings,
and the influence of such loads on the stresses in the spars is
perhaps of as great importance in the wing design as any other
phase of load distribution. Very little correlated or systemat~
10 data on the distribution of load over wing tips, however, ex—
ist, and the common practice in wing design is to assume a “tip
loss" or reduction in load at the tip which is based on early
wind/tunnel tests. These tests were made on an airfoil With
square tips, and were conducted in such a manner that the results
are somewhat open to question. Later tests have been made on
wings with other forms of tip, but the results of these tests
either are incomplete or have not been correlated to the point
of usefulness in design.

In view, therefore, of the importance of wing tip loads,
and of the lack of systematic or reliable information concerning
such loads, an investigation in flight of the pressure distri—
bution over wing tips has been undertaken by the National Ad—
visory Committee for Aeronautics at Langley Field, Virginia.
This investigation is outlined to include pressure measurements
on the right-upper wing panel of a Douglas MFB airplane with
several Variations in tip plan form, systematic in the main,
but also including a few odd shapes, either because such forms
are commonly used, or because of the facility with which such
forms could be included in the program.