The stability triangle


Stability triangle formula


 Gyroscopic stability factor
 Dynamic stability factor


The dynamic stability condition Go to formula can be expressed in an alternate way. leading to a very illustrative interpretation of bullet stability.
In using a quantity s, according to the above definition, the dynamic stability condition takes a very simple form (see above formula). This means that for a bullet to be gyroscopically and dynamically stable, a plot of s vs. sd has to remain completely within the stability triangle (green area in the figure below).
Stability triangle

 The red areas are regions of gyroscopic stability but dynamic instability: either the slow mode oscillation (left area) or the fast mode oscillation (right area) get umdamped.

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