Introduction to Aircraft Aeroelasticity and Loads

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Introduction to Loads

In this book, the topics covered divide naturally into those related to (a) stability (e.g. flutter), (b) static deformation (e.g. static aeroelastic effects, steady flight manoeuvres) and (c) dynamic response (e.g. manoeuvres, gusts, turbulence). The aircraft dynamic response needs to be calculated for ground manoeuvres (e.g. taxiing, take-off and landing), flight manoeuvres (e.g. response to control movements) and gust/turbulence encounters. However, once the response deformations and accelerations are obtained, the loads and stresses generated in the aircraft must also be determined so that the strength and fatigue/damage tolerance behaviour may be assessed.

‘Loads’ is a general term that incorporates both forces and moments, discrete and distributed, external and internal. In this chapter, various basic concepts relevant to loads in general will be introduced, including Newton's laws of motion for a particle and their generalization to a body, D'Alembert's principle (leading to discrete inertia forces/couples and distributed inertia forces), externally applied/reactive loads, free body diagrams (FBDs), loads generated internally within a structure (i.e. internal loads) and intercomponent loads. It will be shown how loads within a structure may be determined in an accelerating slender member by introducing distributed inertia loads so as to bring the structure into an effective static equilibrium condition.

In this chapter, the way in which internal loads ...