Ground Effect on the Longitudinal Stability of an Unmanned Airplane

Abstract

Universidad Simon Bolivar, Naiguata, Edo. Vargas, 1160, Venezuela The objective of the present study is to analyze the effect of ground proximity on the longitudinal stability of the Unmanned Airplane for Ecological Conservation (ANCE). First, the original system of equations that describes the effect of variations of vertical distance was modified in order to consider the influence of ground proximity on the airplane at small angles of attack. The stability coefficients at different heights were computed using the low–order panel code CMARC. Then, the static characteristics were estimated, and a dynamic analysis was performed. The implication of the h derivatives on the aircraft dynamic stability was studied by writing two groups of equations of motion, one includes the h derivatives, and the other one assumes these ones equal to zero. The eigenvalues for each case were calculated at different heights above ground. It can be concluded that the h derivatives have a strong influence on the longitudinal dynamic stability in ground effect, and it would be a mistake to consider only the stability coefficients at a given height to study the dynamic stability of an aircraft in ground effect neglecting the h derivatives.