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Daniel Guggenheim School of Aerospace Engineering

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Zero-Emission Regional Aviation in Sweden

2022-11 , Sorrentino, Robert T. , Parello, Romain C. , Delage, Martin , Justin, Cedric Y. , Mavris, Dimitri N. , Jouannet, Christopher , Amadori, Kristian

Regional air operations, which can be defined as the transportation of passengers using smaller aircraft over short distances, have been overlooked in recent years by airlines focusing on high volume and profitable routes between large airports. Despite this shift of focus, the airport infrastructure still exists in many smaller communities between which demand for air travel exists. The emergence of new air vehicles designed for shorter routes could stimulate efficient and profitable operations, especially if they leverage currently underutilized and paid-for airports. However, new regional air operations need to be sustainable to be successful in a world striving for a carbon-neutral future, especially since air travel over short distances can be substituted by other means of transportation with a smaller environmental footprint such as cars, trains, or buses. Many different paths are envisioned to reach zero-emission goals. These range from technology advancements to new powertrain configurations, and from new transportation policies to new emission offsetting schemes. It is however not clear how these different paths interact and how solutions could be optimally combined. Analyses are therefore required to estimate future demand for air travel and to assess the feasibility of zero-emission regional aviation with the objective to support decision-making about viable and sustainable paths for new regional air operations. The developed modeling environment is implemented in Sweden and allows for an environmental assessment of various scenarios. Significant untapped demand is uncovered between smaller markets, and given fuel and energy consumption for these operations, it is likely that sustainable advanced regional air mobility will be possible in Sweden provided technology transitions can be made.

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Trajectory Energy Management Systems for eVTOL Vehicles: Modeling, Simulation and Testing

2022 , Wilde, Markus , Kish, Brian , Senkans, Emils , Kanchwala, Tahir , Beedie, Seumas M. , Harris, Caleb , Verberne, Johannes , Justin, Cedric Y. , Merkt, Juan

The rise of electric aircraft propulsion methods, 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 lead to novel technical and regulatory challenges for aircraft manufacturers, certification authorities and operators. The combination of electric propulsion, where energy reserves and powertrain performance are highly sensitive to the environment, and VTOL, where the aircraft cannot simply glide to an emergency landing, generates the need for Trajectory Energy Management (TEM). The TEM task involves the manipulation of flight and propulsion controls to achieve a planned flight profile. The TEM system must provide the pilot or automated control system with guidance cues to achieve a planned flight profile, to maintain an energy-optimal trajectory, to avoid deviations from the flight plan causing increases in energy and power consumption, and to mitigate the risk of energy completion. As the pilot must manage both the energy source and flight dynamics energy state, the TEM system must provide sufficient information to the pilot, so that the pilot can perform the mission. 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. These requirements must be defined based on prototype algorithm development, simulation results, and flight test data.

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Impact of Adverse Weather on Commercial Helicopter Pilot Decision-Making and Standard Operating Procedures

2021-08 , Speirs, Andrew H. , Ramee, Coline , Payan, Alexia P. , Mavris, Dimitri N. , Feigh, Karen M.

Helicopter pilots face unique challenges with regard to adverse weather when compared to fixed-wing pilots. Rotorcraft typically operate at lower altitudes in off-field areas that are not always well covered by weather reporting stations. Although recent technological advances have increased the amount of weather data that pilots can access in the cockpit, weather remains a factor in 28% of fatal helicopter accidents. In this work, commercial helicopter pilots were surveyed and interviewed to better understand how they gather and process weather information, what the perceived limitations of current weather tools are, and how their decision-making process is affected by the information they gather and/or receive. Pilots were found to use a wide variety of weather sources for their initial go or no-go decision during the preflight phase, but use fewer weather sources in the cockpit while in-flight. Pilots highlighted the sparsity and sometimes inaccuracy of the weather information available to them in their prototypical operational domain. To compensate, they are forced to rely on local and experiential weather knowledge to supplement weather reports while still working to mitigate other external pressures. Based on the literature and on results from this work, recommendations are made to address the weather-related gaps faced by the rotorcraft community. This includes the installation of additional weather reporting stations outside of airports and densely populated areas, the further promotion of the HEMS tool to helicopter pilots in all industries, the development of weather tools capable of visualizing light precipitation such as fog, and the development of in-flight graphical displays that can help reduce the cognitive workload of interpreting weather information.

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Modeling and Simulation of Novel Electric/Hybrid Electric Multicopter Architectures for Urban Air Mobility

2021-08 , Demers Bouchard, Etienne , Verberne, Johannes , D’Arpino, Matilde , Ozcan, Metin , Porpora, Francesco , Gladin, Jonathan C. , Patel, Srujal , Justin, Cedric Y. , Mavris, Dimitri N.

This paper introduces a dynamic simulation environment developed for novel multi-copter aircraft architectures. The development is motivated by the need to better understand the safety implications of architectural design choices and to provide a formal reliability assessment framework for new Vertical Take-Off and Landing (VTOL) concepts able to consider various airframe and subsystems dynamic behavior. The concepts of interests are different multi-copters configurations investigated by NASA and featuring either electric, hybrid electric, or turboshaft driven powertrains. The simulation environment is a timemarching dynamic simulator formulated using physics-based subsystem models for the batteries, electric motors, turboshaft engines and electric generators. Identified fault modes are integrated into the subsystem models for subsequent use during reliability assessments. The impacts of subsystem faults are propagated to the vehicle flight dynamic response for analysis of their impact on the ability of the vehicle to sustain safe operations. Detailed features of the electric quadrotor model are provided to illustrate the simulation capabilities. Some faults are inserted on the different aircraft in hover and the subsystems behavior is successfully propagated at the vehicle level.

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Development of a Simulation Environment to Track Key Metrics to Support Trajectory Energy Management of Electric Aircraft

2022-07 , Verberne, Johannes , Beedie, Seumas M. , Harris, Caleb , Justin, Cedric Y. , Mavris, Dimitri N.

Growing concerns worldwide about anthropogenic climate change are leading to significant research in ways to reduce greenhouse gas emissions. Technologies are investigated to improve the overall energy efficiency of flying vehicles, and among these, new powertrain technologies less reliant on fossil fuels are especially promising. Concurrently, the expected growth of new market segments, such as urban air mobility and regional air mobility where vehicles are envisioned to operate over densely populated areas, will lead to increased scrutiny regarding the vehicle emissions and the vehicle safety. In this context, significant research has been carried out in the field of electric and hybrid-electric aircraft propulsion. Driven by significant strides made by the automotive industry regarding electric battery technology, the aspirational goal of useful electric flight is now within reach. Significant challenges nonetheless remain regarding the certification of these new vehicles to ensure an equivalent level of safety. Indeed, the behavior of electric powertrains is more complex than that of traditional powertrains and features additional thermal and ageing constraints that need to be contended with. Moreover, the ability of many of these vehicles to fly both on their wing or on their rotors brings another level of sophistication that will increase the workload of flight crews. Combined, these might adversely impact the safety of flight. This research aims to elucidate some of these challenges by providing insights into the behavior and idiosyncracies of new electrified vehicles and by identifying visual cues that should be provided to flight crews to support safe decisionmaking in the cockpit. Besides these visual cues, we explore functionalities that a Trajectory Energy Management system could feature to improve flight safety by providing insights into the management of stored usable energy and by monitoring critical parameters of electrified powertrains. This paper includes two use-cases in which the functionality of the Trajectory Energy Management system is explored for pre-flight planning and in-flight diversion decisionmaking applications.

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Emergency Planning for Aerial Vehicles by Approximating Risk with Aerial Imagery and Geographic Data

2022-01 , Harris, Caleb M. , Kim, Seulki , Payan, Alexia P. , Mavris, Dimitri N.

Urban Air Mobility and Advanced Air Mobility require the certification of novel electrified, vertical takeoff and landing, and autonomous aerial vehicles. These vehicles will operate at lower altitudes, in more dense environments, and with limited recovery abilities. Therefore, emergency landing scenarios must be considered broadly to understand the risks in some situations of flight failures. This work provides a preflight planning tool to assist these vehicles when emergency landing is required in crowded environments by fusing geographic data about the population, geometric data from lidar scans, and semantic data about land cover from aerial imagery. The Pix2Pix Conditional GAN is trained on Washington D.C. datasets to predict eight classifications at a 1m resolution. The information from this detection phase is transformed into a costmap, or riskmap, to use in planning the path to the safest landing locations. Multiple combinations of the cost layers are investigated in three test scenarios. The Rapidly Exploring Random Tree (RRT) algorithm efficiently searches for an alternative path that minimizes risk during emergency landing. The tool is demonstrated through three scenarios in the D.C. area. The objective is that the tool allows for the safe operation of UAM and AAM vehicles through crowded regions by providing confidence to the local population and federal regulators.

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Performance Assessment of a Distributed Electric Propulsion System for a Medium Altitude Long Endurance Unmanned Aerial Vehicle

2021-08 , Markov, Alexander A. , Cinar, Gokcin , Gladin, Jonathan C. , Garcia, Elena , Denney, Russell K. , Mavris, Dimitri N. , Patnaik, Sounya S.

Distributed propulsion systems are enabled by electrified aircraft and can provide aero-propulsive benefits. The magnitude and impact of these benefits rely on the location of propulsors on the vehicle, the amount of propulsive force generated by those propulsors, vehicle geometry, and the extent of hybridization of the propulsion system. With an increased number of degrees of freedom over conventionally electrified aircraft, the full extent of the impacts of this technology have not yet been explored, especially for military applications. This study builds on a previous one that implemented a series hybrid and turboeletric propulsion architecture on a turboprop UAV, by introducing a distributed electric propulsion system on the same vehicle. The previous study showed that with a hybrid architecture, the same performance, in terms of range and endurance, could not be achieved for a fixed gross take-off weight. This study investigates the impact of the distributed propulsion system with the goal of identifying the benefits over the previous vehicle and determining the level of technology required to break even with the conventional propulsion UAV. In incorporating the new propulsion system, the engine and main motor are resized, leading edge wing mounted propellers and motors are added to the configuration, and a new battery sizing strategy is implemented. Preliminary results show that, although this new system shows increased range and endurance over the series hybrid vehicle, it still falls short compared to the conventional vehicle with current levels of technology. Although improvements are needed to the electrical system technology to reduce the weight enough to break even with the conventional system, the new vehicle shows increased performance during climb, and has the capability to store energy during the mission. With the proper power management and battery utilization strategies, this system can provide reduction in fuel burn and improved performance during certain phases of the mission which could be beneficial for military applications.

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Optimal Trajectory and En-Route Contingency Planning for Urban Air Mobility Considering Battery Energy Levels

2022-06 , Kim, Seulki , Harris, Caleb , Justin, Cedric Y. , Mavris, Dimitri N.

Urban Air Mobility (UAM) is an electric propelled, vertical takeoff and landing (eVTOL) aircraft envisioned for transporting passengers and goods within metropolitan areas. Planning UAM flights will not be easy as unexpected wind turbulence from high-altitude structures may impact the vehicles operating at a low altitude. Furthermore, considering the short travel time of the UAM, smart and safe decision-making will be challenging, particularly in off-nominal situations that force the aircraft to divert to an alternate destination instead of landing at the initially planned destination. To overcome these challenges, this research proposes automated pre-flight and in-flight contingency planning systems to assist in both normal and irregular UAM operations. A planner in the pre-flight planning system optimizes an aerial trajectory between the scheduled origin and destination, avoiding restricted high-level structures and estimating energy levels. In the contingency planning system, an in-flight replanner produces several optimal trajectories from where the diversion is declared to each alternate destination candidate. A diversion decision-making tool then scores a list of candidates and selects the best site for diversion. Real-world operational scenarios in the city of Miami are presented to demonstrate the capability of the proposed framework.

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Machine Learning Enabled Turbulence Prediction Using Flight Data for Safety Analysis

2021-09 , Emara, Mariam , dos Santos, Marcos , Chartier, Noah , Ackley, Jamey , Puranik, Tejas G. , Payan, Alexia P. , Kirby, Michelle R. , Pinon, Olivia J. , Mavris, Dimitri N.

The hazards posed by turbulence remain an important issue in commercial aviation safety analysis. Turbulence is among the leading cause of in-flight injury to passengers and flight attendants. Current methods of turbulence detection may suffer from sparse or inaccurate forecast data sets, low spatial and temporal resolution , and lack of in-situ reports. The increased availability of flight data records offers an opportunity to improve the state-of-the-art in turbulence detection. The Eddy Dissipation Rate (EDR) is consistently recognized as a reliable measure of turbulence and is widely used in the aviation industry. In this paper, both classification and regression supervised machine learning models are used in conjunction with flight operations quality assurance (FOQA) data collected from 6,000 routine flights to estimate the EDR (and thereby turbulence severity) in future time horizons. Data from routine airline operations that encountered different levels of turbulence is collected and analyzed for this purpose. Results indicate that the models are able to perform reasonably well in predicting the EDR and turbulence severity around 10 seconds prior to encountering a turbulence event. Continuous deployment of the model enables obtaining a near-continuous prediction of possible future turbulence events and builds the capability towards an early warning system for pilots and flight attendants.

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Analysis of Weather-Related Helicopter Accidents and Incidents in the United States

2021-08 , Ramee, Coline , Speirs, Andrew H. , Payan, Alexia P. , Mavris, Dimitri N.

Helicopters typically operate at lower altitudes than fixed-wing aircraft and can take-off and land away from airports. Thus, helicopter pilots have decreased access to weather information due to connectivity issues or sparsity of weather coverage in those areas and at those altitudes. Moreover, regulations allow most rotorcraft to operate in marginal weather conditions. Therefore, weather is a challenge to rotorcraft operations. In this study, rotorcraft events in the United States between 2008 and 2018 in which weather was determined to be a factor are analyzed using the National Transportation Safety Board aviation database. Results show that weather was a factor in 28% of rotorcraft fatal accidents. Wind was involved in most incidents but more rarely involved in fatalities. Bad visibility conditions due to a combination of low illumination and clouds were responsible for most fatal weather-related accidents. Personal flights had the highest accident and incident rates. Finally, the Helicopter Air Ambulance industry had the largest number of incidents and accidents related to visibility conditions out of all other industries. The authors recommend improving awareness of the conditions in which weather events occur and improving training to maintain control of the aircraft in windy conditions or during inadvertent instrument meteorological conditions.

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