  Present work deals with the dynamics of vehicles which intentionally operate
in the ground proximity. The dynamics in ground effect is influenced by the
vehicle orientation with respect to the ground, since the aerodynamic force and
moment coefficients, which in turn depend on height and angle of attack, also
vary with the Euler angles. This feature, usually neglected in the
applications, can be responsible for sizable variations of the aircraft
performance and stability. A further effect, caused by the sink rate,
determines unsteadiness that modifies the aerodynamic coefficients. In this
work, an analytical formulation is proposed for the force and moment
calculation in the presence of the ground and taking the aircraft attitude and
sink rate into account. The aerodynamic coefficients are firstly calculated for
a representative vehicle and its characteristics in ground effect are
investigated. Performance and stability characteristics are then discussed with
reference to significant equilibrium conditions, while the non-linear dynamics
is studied through the numerical integration of the equations of motion.
