The paper presents a missile autopilot design using a recently developed extended mean assignment (EMA) control technique for linear time varying (LTV) systems. The EMA control technique is based on a new series D-eigenvalue (SD eigenvalue) concept in a way similar to the conventional pole placement design for linear time invariant (LTI) systems. The autopilot is to control the nonlinear, time varying pitch axis dynamics of a hypothetical tail controlled missile, which has been used as a benchmark in a number of recent studies on nonlinear, gain scheduling design techniques. A significant improvement of the EMA controller over the previous design is that the new EMA controller uses complex value SD-eigenvalues to avoid singularities known as finite escapes. The nonlinear dynamics of the missile is rendered into a linear one that is tractable by the EMA control technique via the classical linearization along a nominal normal acceleration profile, followed by a linear coordinate transformation. This is the first application of the EMA control to a state space LTV model that is not in the phase variable canonical form. Simulation results are presented for the zero input stabilization; the complete tracking problem will be studied in Part II of the paper.