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National Advisory Committee for Aeronautics, Report - Summary of Methods for Calculating Dynamic Lateral Stability and Response and for Estimating Lateral Stability Derivatives

A summary of methods for making dynamic lateral stability
and response calculations and for estimating the aerodynamic
stability deriratires required for use in these calculations is pre—
mntrd. The processes of performing calculations of the time
histories of lateral motions, of the period and damping of these
motions. and of the lateral stability boundaries are presented as
a series of simple straightforimrd steps. Eristing methods for
estimating the stability derivatives are summarized and. in
mutt? cases. simple new empirical formulas are presented. Ref-
erence is also made to reports presenting experimental data
that should be useful in making estimates of the derivatires.
Detailed estimation methods are presented for low—subsonic-
speerl conditions but only a brief discussion and a list of refer-
mces are given for transonic- and supersonic-speed conditions.

Dynamic lateral stability has not received widespread
attention in the past because it has not generally been a
serious problem in the design of airplanes. Consideration
of dynamic lateral stability has recently become more im-
portant. however, because current design trends toward the
use of low aspect ratio, sweepback, and higher wing load-
ing have, in many cases, led to unsatisfactory dynamic lat-
eral stability. Airplane designers are therefore finding it
necessary to make such calculations in connection with the
design and modification of airplanes. In many cases these
calculations are difficult to perform for designers who have
had no previous experience in theoretical stability work
because most of the published theoretical analyses are not
presented in a form that is especially suited to the compu-
tation of dynamic stability. The estimation of the stability
derivatives required in dynamic stability calculations has
also been found to be difficult in many cases. Although
theoretical and experimental data on these derivatives have
appeared in numerous publications, no single publication has
presented methods for estimating the derivatives for all
types of airplanes.