Active control of a modern fighter aircraft

Many of the active control technology (ACT) systems discussed in this chapter can be found in modern fighter aircraft. Most have been designed using modern control methods, such as the optimal linear quadratic regulator problem, to determine the appropriate feedback control law. Other methods such as model-following or eigenstructure assignment can be used with equal facility, but the resulting control law will take the same form namely a linear full, state-variable feedback control law. When gust load alleviation (GLA) or bending mode control (BMC) are being considered, where the most significant bending modes are taken into account, the corresponding feedback control will require that the bending displacements and rates are available for measurement. This may be unlikely, and if those methods are to be employed, then recourse to state estimation techniques will be required.