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National Advisory Committee for Aeronautics, Technical Notes - Correlation of Calculation and Flight Studies of the Effect of Wing Flexibility on Structural Response Due to Gusts

Studies made to evaluate the influence of wing bending flexibility
on the structural response to gusts of two twin-engine transports and
one four—engine bomber are summarized. The studies encompass some pre-
viously reported and some new flight studies, some calculation studies
based on discrete- or single-gust encounter, and some new calculation
studies for continuous-turbulence encounter, based on the methods of
generalized harmonic analysis. It is shown that the discrete-gust
approach reveals the general nature of the flexibility effects and leads
to qualitative correlation with flight results. The studies based on the
harmonic-analysis approach show good quantitative correlation with flight
results and allow for a much greater degree of resolution of the flexi—
bility effects. The good agreement shown suggests that a suitable approach
for calculating flexibility effects is now available.

This paper presents a summary of results obtained in flight and
analytical studies which deal with the effect of wing flexibility on the
structural response of an airplane in flight_through rough air. The
particular purpose of the paper is to show the degree of correlation that
can be obtained between the flight—test and analytical results, and
through this correlation to assess how well these flexibility effects may
be analyzed.

Specifically, the following material is covered. The significant
results of published flight tests are reviewed and some results of recent
unpublished tests are given. Some results of studies made on the basis
of single- or discrete-gust encounter are then reviewed and the extent of
the correlation with flight—test results is indicated. Finally, some
recent analytical work on the more realistic conditions of continuous-
turbulence encounter, based on the application of the method of general-
ized harmonic analysis, is presented and correlation with flight tests
shown.

In order to permit earlier publication, the present paper has been
confined largely to the significanttfindings of the investigations and
details of the mathematical derivations have been omitted.