Novel approach for angles calibration of air-data systems with inertial measurements

The flow angles calibration of air-data systems is based on the availability of high-accuracy reference measurements of angle-of-attack and sideslip angles. Typically, these are obtained by auxiliary sensors directly providing the reference angles (e.g., nose-boom vanes) or by analytically reconstructing them using calibrated airspeed measurements and inertial data. This paper proposes a novel approach in which the reference data for the flow angles calibration are obtained by inertial measurements only. The methodology, aiming to lower the development costs of advanced aircrafts, is developed and validated with reference to the triple-probe air-data system of a Piaggio Aerospace Medium Altitude Long Endurance Unmanned Aerial System. Specific flight tests are carried out for the calibration process, by defining maneuvers that reduce flight time and facilitate the calibration itself. The technique is made of two steps: first, the aloft wind speed is estimated, and the angle-of-attack and sideslip angles are reconstructed; next, the reference data are used to define the calibration polynomials via least-mean squares approximation. The approach effectiveness is presented and discussed with reference to flight tests with three different configurations of flaps extension, by comparing the calibrated results with the data coming from high accuracy nose-boom vanes.