Abstract: The application of H _∞ control theory to flight dynamics problems is studied. The lateral directional maneuver of a representative aircraft is used as an example. The flight control system design problem is formulated as the standard H _∞ control problem. The H _∞ controller is designed for the generalized plant in order to improve the robustness. The explicit model following technology is used in which the desired flying qualities are embedded in ideal models of the sideslip angle and stability axis roll rate responses to commanded inputs. The control objective is met by minimizing the weighed error between the ideal model outputs and the actual plant outputs; at the same time, all the control surfaces are not saturated. Numerical computations indicate that the generalized plant can attain desired performance and robustness despite uncertainties in the aircraft's aerodynamic coefficients.

Key words: H _∞ contr ol theor y, flight control syst em, r obustness