Report presenting the results of a limited research program initiated to study the effects of a hot propulsive jet on the longitudinal stability characteristics of a fighter-type airplane configuration. The data was obtained from a rocket-boosted free-flight model investigation over a range of Mach numbers using four models that differed only in the position and size of the horizontal tail. Results regarding the time histories, trim, normal force, pitching moment, aerodynamic-center location, dynamic stability, trim drag, and pressure data are provided.