Preliminary investigation of the superelastic monostable spoiler for dynamic gust loads alleviation

ifasd2024 Tracking Number 26

Much effort has been made to design aircraft to optimise fuel consumption through reduction of aerodynamic drag. A sizable contribution to the overall drag is lift-induced drag, which could be reduced by increasing the wing span, but such a design solution has well defined limits since it often results in the increment of structural loads, especially in terms of wing bending moment, and consequently wing weight. Aircraft flight and ground loads are the key elements in carrying out the aircraft structural sizing and therefore determining its weight. In order to minimise costs and fuel consumption, aircraft designers aim to achieve minimum structural weight, whilst ensuring that failure cannot occur at any point of an aircraft’s operation and in-service life due to excessive stresses or deflections. Aircraft load alleviation strategies are of particular interest since they allow the mitigation of critical load cases thus preventing oversizing the structure. This paper investigates a novel load alleviation technology named “superelastic mono stable spoiler”. This consists in a passive load alleviation system given by a monostable surface that is passively deployed when the local structural strain is higher than a given threshold value and passively stow back when the strain is reduced. Such a surface, when located on the top part of the aerodynamic airfoil, is supposed to obstruct the incoming aerodynamic flow leading to local flow separation and consequently lift reduction. Such a working mechanism allows the “superelastic mono stable spoiler” (SMS) to act as a passive loads alleviation system that passively pops up only when needed and it is supposed to be not activated in normal cruise conditions. This paper will present a number of trade studies looking at the impact of different activation thresholds and deflection rate of the “superelastic mono stable spoiler” on the aircraft gust dynamic response. A representative civil aviation model will be used and all the analyses will be done using a linear time marching unsteady gust simulation formulation based on doublet lattice method for the aerodynamics and modal condensation for the structure. Initial preliminary results show promising loads alleviation capability in a one minus cosine gust encounter.