Optimal trends in Manoeuvre Load Control at subsonic and supersonic flight points for tailless delta wing aircraft

Manoeuvre Load Alleviation (MLA) is the concept of redistribution of forces and moments on airframe through optimal actuation of control surfaces. The effect is to minimise the stresses near wing root and improve fatigue life of airframe components, such as, the frequently studied wing root fitting connecting wing to the fuselage. The configuration is a typical tailless delta wing aircraft having inboard and outboard Elevons (a combination of Elevator and Aileron) placed symmetrically on starboard and port side. The problem is formulated as minimisation of independent conflicting multiple objectives of wing root bending and twisting moments, with stability equations as equality constraints and actuator hinge moments as inequality constraints. Hybrid method is used as optimisation technique, which is evolved from the combination of heuristic based Elitist non-dominated Sorting Genetic Algorithm (NSGA-II) and calculus based Goal Programming methods. The primary objective of this paper is to bring out the structural benefits attainable for some of the combined critical manoeuvre load cases at subsonic and supersonic flight points. The combined critical manoeuvre load cases demarcate the limit to which airframe is loaded. The minimisation achieved is better for flight points at supersonic as compared to subsonic Mach numbers.