During the last two decades, the interest in civil and military high speed
marine vehicles has lead to several new configurations. Some of them exploit a
combination of aerodynamic and hydrodynamic forces to sustain part of the weight
of the craft, leading to a hybrid vehicle (HV). This paper focuses on the study
of the longitudinal high-speed dynamics of such hybrid vehicles. Since airborne
and waterborne vehicles belong to two distinct areas of research, they have been
investigated with a rather different approach. The authors propose a unified
mathematical model to represent the kinematics suitable for hybrid vehicles,
including a detailed analysis of the aerodynamic and hydrodynamic forces acting
on the vehicle. Then a set of ordinary differential equations of motion is
derived in the frame of small-disturbance stability theory, leading to the
Cauchy standard form. An illustrative example of a hybrid vehicle (KUDU II) is
analyzed with the proposed method