Calibration of a Nose Boom Mounted Airflow Sensor on an Atmospheric Research Aircraft by Inflight Maneuvers

Abstract

The document demonstrates the complete calibration of an air data sensor on the German atmospheric research aircraft HALO. The airflow probe which is mounted on the tip of a nose boom measures static and dynamic pressure as well as the two airflow angles: angle of attack and angle of sideslip. These four units and a temperature measurement are required to calculate the complete 3-dimensional airflow vector which is used for flight testing as well as for the determination of the wind speed vector in atmospheric research. The report is based on the preceding static source calibration of this sensor by means of a trailing cone which is documented in a preceeding DLR Forschungsbericht (2019-07). The document demonstrates step by step how to determine the necessary corrections which are required to calculate the true airflow vector with extremely small measurement errors and a high temporal resolution. The calibration uses known properties of the atmospheric wind and therefore requires the establishment of a 3-dim wind measurement on the aircraft. The necessary experimental flight test effort concerns static calibration procedures for the mean air data units as well as dynamic maneuvers which are required to investigate the response of the experimental air data system to fast airflow fluctuations. The dynamic corrections prove that the direct measurement of vertical and horizontal wind fluctuations shows a directional sensitivity which must be corrected if the data is used for meteorological investigations. (Published in English)