To study the longitudinal motion of the submerged body, the fundamental equations of motion and kinematic relationships of the motion coordinates were established, and then by use of proper assumptions, the equations of motion were linealized to obtain equations amenable to analytic solution by perturbation methods.
The characteristics of the eigen values of the equations of motion of the typical model due to the changes in Froude number, and proper stability derivatives were discussed by the use of Root Locus Method and the results of the solution by the digital computer.