Safety Assessment for Certified Air Data Systems based on Synthetic Sensors

The work deals with safety assessment for the innovative modular digital air data system developed under the MIDAS project, funded in the Clean Sky 2 frame. The MIDAS's main innovation is based on estimation of aerodynamic angles (angle of attack and sideslip) using synthetic sensors instead of classical vanes (or sensors), whereas pressure and temperature are directly measured with Pitot and temperature probes. As known, air data systems are safety-critical ones that are usually redundant in order to be compliant with the safety requirements of airworthiness regulations. In order to meet safety objectives, a single (simplex) ADS is studied in order evaluate its own safety characteristics starting from reliability known data for any air data system items. These results are then collected in order to provide necessary information to the aircraft integrator that is in charge to define the system redundancy. The present paper introduces the common aeronautical procedures for system safety assessment to be applied to a safety critical system based on synthetic sensors for the first time. Standard procedures are applied to the MIDAS project in order to evaluate its safety characteristics with respect to safety objectives defined at aircraft level in accordance with the aircraft integrator. Results shown in this work provide information on criticality allocated to any air data functionalities that will be used to study the overall ADS redundancy.