Air Data Computation in Fly By Wire Flight Control Systems

The aim of the air data system is the determination of flight parameters (such as pressure altitude, Mach number, angles of attack and sideslip) from measurements of local pressures and of local flow angles on wings or fuselage provided by a proper set of sensors. The "active" and "integrated" use of flight parameters in a full-authority Fly by Wire Flight Control System imposes the system architecture to be redundant, in order to achieve the adequate level of reliability and safety. In this paper a methodology for the air data computation is proposed which allows the above mentioned flight parameters to be evaluated on the basis of data measured by four multi-function air data probes. It takes into account the effects of the modification of aircraft configuration during flight, as well as the effects of aircraft manoeuvres. Finally, it includes dedicated algorithms for the management of redundancy, which are able to detect possible system failures and to provide consolidated outputs. The methodology has been implemented in the Matlab/Simulink environment and a preliminary comparison of the results with flight test data outlined satisfactory performance.