For the purpose of this paper, certain fundamental parameters are assumed to be outside the control of the structures designer. It is, however, realised that the designer is often able to show that small changes in one or more of these parameters may have far-reaching effects.

These basic parameters include the aircraft size, weight, operating speed and altitude, aerodynamic characteristics and load factors. Fig. 1 shows how these combine together in various ways to give the loads acting on the structure, the temperature environment and the stiffness required to prevent aeroelastic disturbances.