Stability and Performance of a Light Unmanned Airplane in Ground Effect

Abstract

The objective of the present work is to understand the effect of ground proximity on the aerodynamic performance and stability of a light unmanned aerial vehicle. The flowfield around the airplane was computed by PAN AIR and Athena Vortex Lattice. The ground effect was simulated using the method of images. The stability coefficients and other aerodynamic characteristics were obtained at different heights above ground and in free flight. The results demonstrate that the airplane is lateral-directional statically stable, longitudinal statically stable in free flight and longitudinal statically unstable in ground effect. The dynamic stability characteristics of the airplane were obtained at different heights above ground. The phugoid mode is considerable influenced by ground effect and a divergent and non-oscillatory mode appears when the airplane is near to the ground. This is called non-dimensional height mode. The short-period, the Dutch roll, the roll and the spiral modes are slightly affected by ground effect. Significant differences were obtained when the z derivatives were neglected in the dynamic analysis for longitudinal motion. The present work demonstrates that the performance and stability of the unmanned airplane are considerably influenced by ground effect.