An experimental study on the effects of adverse weathers on the flight performance of an Unmanned-Aerial-System (UAS)
An experimental UAS was developed to study the effects of adverse weathers, including icing and strong winds, on the UAS flight performance. Sensors were integrated on board the UAS to take in-situ, time-resolved measurements of atmospheric parameters, including temperature, humidity, pressure, wind direction and speed, during the flight. The measurement results of the atmospheric parameters were correlated with the UAS altitude data, and the UAS power consumption data to elucidate the underlying physics for a better understanding of the effects of the adverse weathers on the flight performances. Test flights were fully autonomous between takeoff and landing. The experimental portion of the flight had fixed geolocation and trajectories in the designed missions. The flights resulted in comparison of circular loiter data between calm, windy and icing conditions. Variations in the UAS power consumption were investigated during different segments of each flight. Glaze ice accretion was found to result in the malfunction of pitot static tube causing the loss of air speed data. Furthermore, wing leading edge and propeller icing resulted in rapid increase in the power consumption. It was discovered that ice accretion caused the greatest power consumption during the flight. Then, windy condition had the second highest power consumption with strong headwinds. Power consumption also spiked when turning against crosswinds from an initial tailwind condition. Iced propeller and vertical tail were preserved for the 3D scanning in the laboratory to quantify the 3-D shapes of the accreted ice structures. While the glaze icing on the UAS propeller resulted in the formation of ice horns and ridges, the main wing of the UAS had mostly leading-edge icing with the formation of runback rivulets on the suction side. Total power consumption in calm, windy and icing conditions during fixed loiter was found to be 10.5 kW, 24.2 kW and 36.1 kW, respectively. The findings derived from the present study highlight the importance of developing effective strategies to ensure safer and more efficient UAS operation under adverse weather conditions.