Multiple solutions for aircraft sideslip behaviour at high angles ofattack

Abstract

This paper advocates the use of total plane aerodynamics to simplify the problems of aircraft aerodynamics/ flight dynamics at high angles of attack. The advantages of this approach are illustrated by considering the problem of aircraft sideslip behaviour at high angles of attack. Force components on aircraft forebodies at combined angies of attack and sideslip are successfully synthesized from zero sideslip data. in addition the wide variety of published Cn v beta c u r v e s for forebodies are shown to be particular examples of the multiple solutions that are possible due to side force switching effects. The value of applying this approach to complete aircraft is demonstrated by the remarkable agreement obtained between experimental data for the Cn v beta curve of an F-111 and a prediction based on the contribution of its forebody alone. The significance of these multiple solutions to the resultant aircraft motion is discussed and a new wind tunnel testing procedure is advocated to ensure a full discovery of all possible high incidence behaviour. .,