An extensive theoretical study of the ability of slender-wing aircraft to perform sidestep manoeuvres at approach speeds

Abstract

The sidestep manoeuvre is investigated in some detail for a slender-wing aircraft by specifying the bank-angle time history and determining the required control angles. The effect of inclusion of the full inertia terms, the influence of different bank-angle time histories and the consequences of wide variations in the aerodynamic derivatives are examined. It is found that it is not necessary to include the full inertia terms in the equations of motion. An efficient manoeuvre requires a rapid initial growth of roll angle; if this is not achieved, subsequent control demands are large and only a small sidestep distance is achieved. Besides control effectiveness, the most important derivatives are the yawing moment due to aileron, the rolling moment due to rudder and the yawing moment due to rate of roll. Rudder requirements are much greater than aileron requirements. The initial demands for a good manoeuvre or subsequent demands for a poorly executed manoeuvre could be a design case for the rudder. A tentative design criterion is suggested. If the rudder is not used, the large sideslip angles which develop would require the use of excessively large aileron angles. It appears necessary to attempt some co-ordination of the manoeuvre by the use of the rudder. Piloting difficulties may be greatly alleviated by linking the rudder to the aileron.