AERODYNAMICS, DYNAMICS AND PERFORMANCE PREDICTION OF SAILPLANES AND LIGHT AIRCRAFT

Abstract

Aerodynamic characteristic prediction is of crucial importance in order to be able to estimate aircraft performances and dynamic behavior. In this paper capabilities of a PC based computer code (named AEREO) to predict longitudinal and lateral aerodynamic characteristics of light aircraft and sailplanes is presented. Semi-empirical methods are used as main thesis, together with more sophisticated procedures for high angles of attack or more in general non linear conditions.
Aerodynamic prediction is performed in different steps. In a first preliminary step, wing, vertical and horizontal tail airfoils aerodynamic characteristics prediction is performed with a 2D code which has been developed at DPA (Department of Aeronautical Engineering). The output are Cl(a), Cm(a), Cd(a), curves up to stall and post-stall conditions. These curves along all necessary geometrical aircraft characteristics are the input to the AEREO code. In this code an iterative numerical procedure based on the lifting line Prandtl theory is then used for the prediction of loads and moments for the wing and horizontal tail up to stall and post-stall conditions. The aerodynamic curves coming from the AEREO code are used as input for the aircraft motion simulation code called DYNASIM which returns aircraft motion and dynamic behavior for a user specified control law or for an imposed air disturbances. This code solves the general 6 degrees of freedom equations using non-linear aerodynamics and it offers the possibility to fly the airplane using the mouse as stick command. Simulation of a stall maneuver of a light single engine aircraft has been performed and numerical results are in good agreement with flight data. Comparison between predicted and flight sink polar has been shown for the ASW-24 sailplane.