The development of a total system aircraft landing control scheme

Current aircraft braking systems are independent single loop controlled anti-skid systems. No account is taken of the whole system behaviour or the potential use of the combined aerodynamic and mechanical braking systems. Modern multivariable techniques are used in the development of a control law designed for the purpose of improving landing and braking performance as a total aircraft approach. The problem is to design a braking system that takes into account the all-axis aerodynamic and mechanical behaviour of an aircraft at the point of touchdown and optimises landing performance. The system applies the appropriate aerodynamic and brake control action to cause the aircraft to come to rest in an optimal and controlled manner taking into account weather and runway conditions. The two factors, which are minimised, are runway centre-line offset and landing runway length. The new control scheme uses main wheel braking from the moment the main gear contacts the runway surface and the wheel velocities match that of the ground. The controller also uses the ailerons and main wheel brakes to aid in braking and the ailerons, rudder, nose wheel steering and differential braking to maintain directional stability and evenness of tyre/runway pressure. The paper briefly describes the linear aircraft model used to design the control law, the nonlinear aircraft model used to test the control law and the control rationale.