Calibration and accuracy determination of airdata system for a modern fighter aircraft

An Air data system (ADS) is an essential avionics module found in modern fighter aircraft cockpits. It provides critical information about the aircraft to the pilot throughout the flight regime. Airdata system comprises of air data computer and their associated sensors. Sensors instrumented on aircraft normally measure pressures and flow angles in the local flow field using vanes and probes. However, aircraft requires the free stream parameters for flying. Therefore, forward lookup tables in Air Data Computer (ADC) are used to covert local parameters measured using airdata sensor to free stream parameters. In order to design flight controls, improved system performance, ADS should deliver accurate output. Accuracy of free stream parameters depends upon the accuracy of these tables in Air data computer. In this paper, the airdata system of a modern fighter aircraft is considered. This system carries airdata tables which are calibrated/updated using Maximum Likelihood Estimation (MLE) method. The accuracy of it needs to be determined by another independent technique. Hence an Extended Kalman Filter (EKF) is proposed to calibrate and describe the accuracy limits of airdata system. The technique is tested with flight data and the results demonstrate the strength of the technique for airdata calibration and accuracy determination.