A novel methodology to update table in air data system of a high performance fighter aircraft

Accurate air data parameters and measurements are critical for the successful flight missions of any modern fighters. Externally mounted vanes and probes measure the local flow angles, pressure, and temperature. These local measurements are to be corrected through a calibration process to obtain the free stream flow angles, pressure, and ambient temperature, etc. The preflight calibration of these sensors are carried out using wind tunnel tests/CFD computations. This paper presents a novel methodology to update air data table of these sensors, post-flight. The Air Data Computer (ADC) of the aircraft discussed in this paper hosts air data tables that are pre-calibrated using the Maximum Likelihood Estimation (MLE) method. However, challenges have been experienced in extending MLE methods for unsteady flights, when dynamic effects prevail. Unsteady conditions during wind up turns are inevitable to perform calibration at High Angles of Attack (AoA) regimes. Hence, an extended Kalman filter based methodology is proposed for calibration and table update. A complete process is tested for an entire flight envelope having 200 and odd flights. The results demonstrate the strength of the technique for air data calibration and table update in ADC.