Introduction to Aircraft Aeroelasticity and Loads

24

Flight Manoeuvre and Gust/Turbulence Loads

In this chapter, the different ways in which flight manoeuvres and gusts are handled in industry when seeking type certification are discussed. The wide range of different cases that have to be considered is examined. From these bookcase and rational design calculations, the internal loads can be determined which then are used to calculate the stresses.

In Chapter 25, the corresponding issue of ground manoeuvre loads will be considered. Also in Chapter 25, the calculation of stresses from internal loads (via loads acting upon components) and loads sorting will be considered briefly. Once again, it should be pointed out that the treatment in this book stops at the generation of shear forces, bending moments, torques, etc., and does not cover calculation of stresses in any detail.

24.1 EVALUATION OF INTERNAL LOADS

In all the following manoeuvre/gust cases, the internal loads and other interesting quantities may be extracted from the response and applied force time histories using the ‘mode displacement’, ‘mode acceleration’ or ‘force summation’ approaches (CS/AMC 25.341). The ‘force summation’ method was illustrated in Chapter 18, showing how suitable transformation matrices allowed summation of inertial and aerodynamic effects via an auxiliary equation when generating internal loads.

It should be noted that in this book, ‘internal’ loads (as far as the whole aircraft is concerned) are taken to be bending moments, shear forces, axial ...