Flight Tests of Trajectory Energy Management Systems Using a Vertical Takeoff and Landing Vehicle
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The rise of new aircraft propulsion methods (e.g. powered by batteries, fuel cells or hybrid electric systems), the increased use of automated and integrated flight control systems, and the envisioned use of personal Vertical Takeoff and Landing (VTOL) vehicles in urban environments (urban aerial mobility) leads to novel technical and regulatory challenges for aircraft manufacturers, certification authorities and operators. Of primary concern is operational safety, and closely connected pilot situation awareness and workload. A particular safety factor for operating VTOL vehicles that depend on propulsive lift for the majority of their operations and that are operated over urban terrain, is the management of energy and power needs along with power and energy reserves. These reserves are highly sensitive to the environment (mostly temperatures), and with VTOL, where the aircraft cannot simply glide to an emergency landing, management of energy reserves is critical to ensure safe vertical landing after flight. This generates the need for Trajectory Energy Management. This research is intended to define some requirements for energy management such that the pilot can safely accomplish an intended profile and land with enough energy reserves to satisfy the intent of operation rules 91.151 (VFR reserves) and 91.167 (IFR reserves). In the context of trajectory energy management, there is a spectrum of automation tools that may assist the pilot. For example, common avionics systems with moving maps display range rings that help the pilot manage fuel state. These systems make assumptions based on current ground speed, fuel flow and fuel reserve requirements. Requirements for similar tools for VTOL aircraft that employ electric propulsion do not yet exist and must be defined based on prototype algorithm development, simulation results, and flight test data. For higher levels of automation, the Trajectory Energy Management System must be able to define an optimum trajectory for a VTOL aircraft and then couple to an automatic control system to execute that nominal trajectory. This system would need to account for disturbances and off nominal conditions. This project provides solutions and data to help the FAA develop performance estimation tools, flight safety assessment tools and the associated means of compliance for Trajectory Energy Management Systems. Flight tests are used to verify the predicted energy usage and identify potential challenges in operation. Since full scale vehicles are only being developed and are not readily available for testing, a scaled version of electrical VTOL (eVTOL) aircraft was used instead. Scaled vehicle still allows to study power demands in different parts of flight. This thesis provides flight test results of the Trinity F9 drone developed by Quantum-Systems. Prescribed reference missions were flown based on operationally-relevant scenarios. Battery usage for the various flight segments was quantified. Results were compared to analytic models. Finally, lessons learned through the execution of the Trinity F9 flight test program are documented in this thesis. The test objective was to determine the limitations for daily operations of an eVTOL capable Urban Aerial Mobility (UAM)vehicle. Five different reference mission flight profiles were flown for a duration of 2.5 hours, capturing nearly3,000 inflight data points and conducting over 9,000 calculations during data reduction in the production of 20 plots. The results presented are a guide to initial testing of the power and energy management for the tilt rotor Trinity F9 aircraft. Vertical flight phases were found to be most critical as the power demand is 5 to 7 times higher than in horizontal flight. Vehicle is also most likely to overheat during vertical flight limiting the total flight time.